From c81f2dabbc0df96a97556b78b0a697cb8532ca1f Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 19:38:48 +0200
Subject: [PATCH 01/50] add failing test

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 65b38fe67..aa65aec74 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -398,6 +398,20 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn test_invalid_channel_id() -> Result<(), TokenTransferError> {
+        let denom = "transfer/channel-75/factory/stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4/dust";
+        let dt = PrefixedDenom::from_str(denom)?;
+
+        assert_eq!(dt.trace_path.to_string(), "transfer/channel-75");
+        assert_eq!(
+            dt.base_denom.to_string(),
+            "factory/stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4/dust"
+        );
+
+        Ok(())
+    }
+
     #[test]
     fn test_denom_trace() -> Result<(), TokenTransferError> {
         assert_eq!(

From 6c0a324c35600ab46ff0cef191e42b4ab6e16b21 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 20:47:56 +0200
Subject: [PATCH 02/50] add TracePath::new

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index aa65aec74..6444a6338 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -113,6 +113,13 @@ impl Display for TracePrefix {
 pub struct TracePath(Vec<TracePrefix>);
 
 impl TracePath {
+    /// Creates a new trace path from a vector of trace prefixes.
+    /// Reverse the order of the prefixes for easier addition/removal from the end.
+    pub fn new(mut trace: Vec<TracePrefix>) -> Self {
+        trace.reverse();
+        Self(trace)
+    }
+
     /// Returns true iff this path starts with the specified prefix
     pub fn starts_with(&self, prefix: &TracePrefix) -> bool {
         self.0.last().map(|p| p == prefix).unwrap_or(false)

From ad096f5ce913fae22d9a250886cbc16868e22865 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 20:48:28 +0200
Subject: [PATCH 03/50] imp PrefixedDenom parsing

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 38 +++++++++++++++-------
 ibc-core/ics24-host/types/src/error.rs     |  2 ++
 2 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 6444a6338..4f689a7b3 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -301,18 +301,34 @@ impl FromStr for PrefixedDenom {
     type Err = TokenTransferError;
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let mut parts: Vec<&str> = s.split('/').collect();
-        let last_part = parts.pop().expect("split() returned an empty iterator");
-
-        let (base_denom, trace_path) = {
-            if last_part == s {
-                (BaseDenom::from_str(s)?, TracePath::empty())
-            } else {
-                let base_denom = BaseDenom::from_str(last_part)?;
-                let trace_path = TracePath::try_from(parts)?;
-                (base_denom, trace_path)
+        let mut trace_prefixes = vec![];
+
+        let mut remaining_parts = s;
+
+        loop {
+            let parsed_prefix = remaining_parts
+                .split_once('/')
+                .and_then(|(port_id_s, remaining)| {
+                    remaining
+                        .split_once('/')
+                        .map(|(channel_id_s, remaining)| (port_id_s, channel_id_s, remaining))
+                })
+                .and_then(|(port_id_s, channel_id_s, remaining)| {
+                    let port_id = PortId::from_str(port_id_s).ok()?;
+                    let channel_id = ChannelId::from_str(channel_id_s).ok()?;
+                    Some((port_id, channel_id, remaining))
+                });
+            match parsed_prefix {
+                Some((port_id, channel_id, remaining)) => {
+                    trace_prefixes.push(TracePrefix::new(port_id, channel_id));
+                    remaining_parts = remaining;
+                }
+                None => break,
             }
-        };
+        }
+
+        let trace_path = TracePath::new(trace_prefixes);
+        let base_denom = BaseDenom::from_str(remaining_parts)?;
 
         Ok(Self {
             trace_path,
diff --git a/ibc-core/ics24-host/types/src/error.rs b/ibc-core/ics24-host/types/src/error.rs
index 4df4c4dd9..b0b6151e0 100644
--- a/ibc-core/ics24-host/types/src/error.rs
+++ b/ibc-core/ics24-host/types/src/error.rs
@@ -16,6 +16,8 @@ pub enum IdentifierError {
     RevisionNumberOverflow,
     /// String `{value}` cannot be converted to packet sequence, error: `{reason}`
     InvalidStringAsSequence { value: String, reason: String },
+    /// String `{id}` does not start with `{name}`
+    InvalidNamedIndex { id: String, name: String },
 }
 
 #[cfg(feature = "std")]

From 08710f600f96a990299d768eda4f4f51f20336bf Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 20:48:56 +0200
Subject: [PATCH 04/50] add validate_named_u64_index

---
 ibc-core/ics24-host/types/src/validate.rs | 32 +++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/ibc-core/ics24-host/types/src/validate.rs b/ibc-core/ics24-host/types/src/validate.rs
index 47a92ac72..8360d80b3 100644
--- a/ibc-core/ics24-host/types/src/validate.rs
+++ b/ibc-core/ics24-host/types/src/validate.rs
@@ -61,6 +61,38 @@ pub fn validate_prefix_length(
     validate_identifier_length(prefix, min, max)
 }
 
+/// Checks if the identifier is a valid named u64 index: {name}-{u64}.
+/// Example: "connection-0", "connection-100", "channel-0", "channel-100".
+pub fn validate_named_u64_index(id: &str, name: &str) -> Result<(), Error> {
+    let number_s = id
+        .strip_prefix(name)
+        .ok_or_else(|| Error::InvalidNamedIndex {
+            id: id.into(),
+            name: name.into(),
+        })?
+        .strip_prefix('-')
+        .ok_or_else(|| Error::InvalidNamedIndex {
+            id: id.into(),
+            name: name.into(),
+        })?;
+
+    if number_s.starts_with('0') && number_s.len() > 1 {
+        return Err(Error::InvalidNamedIndex {
+            id: id.into(),
+            name: name.into(),
+        });
+    }
+
+    _ = number_s
+        .parse::<u64>()
+        .map_err(|_| Error::InvalidNamedIndex {
+            id: id.into(),
+            name: name.into(),
+        })?;
+
+    Ok(())
+}
+
 /// Default validator function for the Client types.
 pub fn validate_client_type(id: &str) -> Result<(), Error> {
     validate_identifier_chars(id)?;

From 9d2a9eac787e5fb02da5c7f80fdf0fbc46a575f0 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 20:49:26 +0200
Subject: [PATCH 05/50] validate_named_u64_index in channel and connection
 validation

---
 ibc-core/ics24-host/types/src/validate.rs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/ibc-core/ics24-host/types/src/validate.rs b/ibc-core/ics24-host/types/src/validate.rs
index 8360d80b3..6ce26f246 100644
--- a/ibc-core/ics24-host/types/src/validate.rs
+++ b/ibc-core/ics24-host/types/src/validate.rs
@@ -114,7 +114,9 @@ pub fn validate_client_identifier(id: &str) -> Result<(), Error> {
 /// in the ICS-24 spec.
 pub fn validate_connection_identifier(id: &str) -> Result<(), Error> {
     validate_identifier_chars(id)?;
-    validate_identifier_length(id, 10, 64)
+    validate_identifier_length(id, 10, 64)?;
+    validate_named_u64_index(id, "connection")?;
+    Ok(())
 }
 
 /// Default validator function for Port identifiers.
@@ -132,7 +134,9 @@ pub fn validate_port_identifier(id: &str) -> Result<(), Error> {
 /// the ICS-24 spec.
 pub fn validate_channel_identifier(id: &str) -> Result<(), Error> {
     validate_identifier_chars(id)?;
-    validate_identifier_length(id, 8, 64)
+    validate_identifier_length(id, 8, 64)?;
+    validate_named_u64_index(id, "channel")?;
+    Ok(())
 }
 
 #[cfg(test)]

From eba0690056504f33fc6ae1583d8049d5f1889197 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 20:49:44 +0200
Subject: [PATCH 06/50] add tests for validate_named_u64_index

---
 ibc-core/ics24-host/types/src/validate.rs | 50 +++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/ibc-core/ics24-host/types/src/validate.rs b/ibc-core/ics24-host/types/src/validate.rs
index 6ce26f246..b800c1d3b 100644
--- a/ibc-core/ics24-host/types/src/validate.rs
+++ b/ibc-core/ics24-host/types/src/validate.rs
@@ -177,6 +177,25 @@ mod tests {
         assert!(id.is_err())
     }
 
+    #[test]
+    fn parse_invalid_connection_id_indexed() {
+        // valid connection id with index
+        validate_connection_identifier("connection-0").expect("no error");
+        validate_connection_identifier("connection-123").expect("no error");
+        validate_connection_identifier("connection-18446744073709551615").expect("no error");
+    }
+
+    #[test]
+    fn parse_invalid_connection_id_non_idexed() {
+        // invalid indexing for connection id
+        validate_connection_identifier("connection-0123").expect_err("InvalidNamedIndex");
+        validate_connection_identifier("connection0123").expect_err("InvalidNamedIndex");
+        validate_connection_identifier("connection000").expect_err("InvalidNamedIndex");
+        // 1 << 64 = 18446744073709551616
+        validate_connection_identifier("connection-18446744073709551616")
+            .expect_err("InvalidNamedIndex");
+    }
+
     #[test]
     fn parse_invalid_channel_id_min() {
         // invalid channel id, must be at least 8 characters
@@ -193,6 +212,24 @@ mod tests {
         assert!(id.is_err())
     }
 
+    #[test]
+    fn parse_invalid_channel_id_indexed() {
+        // valid channel id with index
+        validate_channel_identifier("channel-0").expect("no error");
+        validate_channel_identifier("channel-123").expect("no error");
+        validate_channel_identifier("channel-18446744073709551615").expect("no error");
+    }
+
+    #[test]
+    fn parse_invalid_channel_id_non_idexed() {
+        // invalid indexing for channel id
+        validate_channel_identifier("channel-0123").expect_err("InvalidNamedIndex");
+        validate_channel_identifier("channel0123").expect_err("InvalidNamedIndex");
+        validate_channel_identifier("channel000").expect_err("InvalidNamedIndex");
+        // 1 << 64 = 18446744073709551616
+        validate_channel_identifier("channel-18446744073709551616").expect_err("InvalidNamedIndex");
+    }
+
     #[test]
     fn parse_invalid_client_id_min() {
         // invalid min client id
@@ -278,4 +315,17 @@ mod tests {
         let result = validate_prefix_length(prefix, min, max);
         assert_eq!(result.is_ok(), success);
     }
+
+    #[rstest]
+    #[case::zero_padded("channel", "001", false)]
+    #[case::only_zero("connection", "000", false)]
+    #[case::zero("channel", "0", true)]
+    #[case::one("connection", "1", true)]
+    #[case::n1234("channel", "1234", true)]
+    #[case::u64_max("chan", "18446744073709551615", true)]
+    #[case::u64_max_plus_1("chan", "18446744073709551616", false)]
+    fn test_named_index_validation(#[case] name: &str, #[case] id: &str, #[case] success: bool) {
+        let result = validate_named_u64_index(format!("{name}-{id}").as_str(), name);
+        assert_eq!(result.is_ok(), success, "{result:?}");
+    }
 }

From dfac6b5f9bc2fd133ee219ef88762537ba44d347 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 20:51:03 +0200
Subject: [PATCH 07/50] update PrefixDenom parsing tests

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 34 +++++++++++++++-------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 4f689a7b3..193d1a5f9 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -380,6 +380,8 @@ impl Display for PrefixedDenom {
 
 #[cfg(test)]
 mod tests {
+    use rstest::rstest;
+
     use super::*;
 
     #[test]
@@ -421,16 +423,28 @@ mod tests {
         Ok(())
     }
 
-    #[test]
-    fn test_invalid_channel_id() -> Result<(), TokenTransferError> {
-        let denom = "transfer/channel-75/factory/stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4/dust";
-        let dt = PrefixedDenom::from_str(denom)?;
-
-        assert_eq!(dt.trace_path.to_string(), "transfer/channel-75");
-        assert_eq!(
-            dt.base_denom.to_string(),
-            "factory/stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4/dust"
-        );
+    #[rstest]
+    #[case(
+        "transfer/channel-75",
+        "factory/stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4/dust"
+    )]
+    #[case(
+        "transfer/channel-75/transfer/channel-123/transfer/channel-1023/transfer/channel-0",
+        "factory/stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4/dust"
+    )]
+    #[case(
+        "transfer/channel-75/transfer/channel-123/transfer/channel-1023/transfer/channel-0",
+        "//////////////////////dust"
+    )]
+    fn test_strange_prefixed_denom(
+        #[case] prefix: &str,
+        #[case] denom: &str,
+    ) -> Result<(), TokenTransferError> {
+        let pd_s = format!("{}/{}", prefix, denom);
+        let pd = PrefixedDenom::from_str(&pd_s)?;
+
+        assert_eq!(pd.trace_path.to_string(), prefix);
+        assert_eq!(pd.base_denom.to_string(), denom);
 
         Ok(())
     }

From be171a19388bc3cf266c7f2cf042a94c42a2e597 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 21:10:22 +0200
Subject: [PATCH 08/50] update accepted cases in ibc-go

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 193d1a5f9..3dbde7655 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -393,16 +393,6 @@ mod tests {
             PrefixedDenom::from_str("transfer/channel-0/").is_err(),
             "empty base denom with trace"
         );
-        assert!(PrefixedDenom::from_str("/uatom").is_err(), "empty prefix");
-        assert!(PrefixedDenom::from_str("//uatom").is_err(), "empty ids");
-        assert!(
-            PrefixedDenom::from_str("transfer/").is_err(),
-            "single trace"
-        );
-        assert!(
-            PrefixedDenom::from_str("transfer/atom").is_err(),
-            "single trace with base denom"
-        );
         assert!(
             PrefixedDenom::from_str("transfer/channel-0/uatom").is_ok(),
             "valid single trace info"
@@ -420,6 +410,13 @@ mod tests {
             "invalid channel"
         );
 
+        // the followings are valid denom according to `ibc-go`
+        // https://github.com/cosmos/ibc-go/blob/e2ad31975f2ede592912b86346b5ebf055c9e05f/modules/apps/transfer/types/trace_test.go#L17-L38
+        PrefixedDenom::from_str("/uatom").expect("no error");
+        PrefixedDenom::from_str("//uatom").expect("no error");
+        PrefixedDenom::from_str("transfer/").expect("no error");
+        PrefixedDenom::from_str("transfer/atom").expect("no error");
+
         Ok(())
     }
 

From e59060ed3b6c0ab86b6121e9a90db442c1844509 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 21:30:53 +0200
Subject: [PATCH 09/50] update accepted cases

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 3dbde7655..0f0bc11f9 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -401,14 +401,6 @@ mod tests {
             PrefixedDenom::from_str("transfer/channel-0/transfer/channel-1/uatom").is_ok(),
             "valid multiple trace info"
         );
-        assert!(
-            PrefixedDenom::from_str("(transfer)/channel-0/uatom").is_err(),
-            "invalid port"
-        );
-        assert!(
-            PrefixedDenom::from_str("transfer/(channel-0)/uatom").is_err(),
-            "invalid channel"
-        );
 
         // the followings are valid denom according to `ibc-go`
         // https://github.com/cosmos/ibc-go/blob/e2ad31975f2ede592912b86346b5ebf055c9e05f/modules/apps/transfer/types/trace_test.go#L17-L38
@@ -416,6 +408,8 @@ mod tests {
         PrefixedDenom::from_str("//uatom").expect("no error");
         PrefixedDenom::from_str("transfer/").expect("no error");
         PrefixedDenom::from_str("transfer/atom").expect("no error");
+        PrefixedDenom::from_str("(transfer)/channel-0/uatom").expect("no error");
+        PrefixedDenom::from_str("transfer/(channel-0)/uatom").expect("no error");
 
         Ok(())
     }

From 04b40dc619d41873b90f412fa9eac78a5dfe6f29 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 21:31:18 +0200
Subject: [PATCH 10/50] add test cases from ibc-go

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 44 ++++++++++++++++++----
 1 file changed, 36 insertions(+), 8 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 0f0bc11f9..42223a7f1 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -427,17 +427,45 @@ mod tests {
         "transfer/channel-75/transfer/channel-123/transfer/channel-1023/transfer/channel-0",
         "//////////////////////dust"
     )]
-    fn test_strange_prefixed_denom(
-        #[case] prefix: &str,
-        #[case] denom: &str,
-    ) -> Result<(), TokenTransferError> {
-        let pd_s = format!("{}/{}", prefix, denom);
-        let pd = PrefixedDenom::from_str(&pd_s)?;
+    // https://github.com/cosmos/ibc-go/blob/e2ad31975f2ede592912b86346b5ebf055c9e05f/modules/apps/transfer/types/trace_test.go#L17-L38
+    #[case("", "uatom")]
+    #[case("", "uatom/")]
+    #[case("", "gamm/pool/1")]
+    #[case("", "gamm//pool//1")]
+    #[case("transfer/channel-1", "uatom")]
+    #[case("customtransfer/channel-1", "uatom")]
+    #[case("transfer/channel-1", "uatom/")]
+    #[case(
+        "transfer/channel-1",
+        "erc20/0x85bcBCd7e79Ec36f4fBBDc54F90C643d921151AA"
+    )]
+    #[case("transfer/channel-1", "gamm/pool/1")]
+    #[case("transfer/channel-1", "gamm//pool//1")]
+    #[case("transfer/channel-1/transfer/channel-2", "uatom")]
+    #[case("customtransfer/channel-1/alternativetransfer/channel-2", "uatom")]
+    #[case("", "transfer/uatom")]
+    #[case("", "transfer//uatom")]
+    #[case("", "channel-1/transfer/uatom")]
+    #[case("", "uatom/transfer")]
+    #[case("", "transfer/channel-1")]
+    #[case("transfer/channel-1", "transfer")]
+    #[case("", "transfer/channelToA/uatom")]
+    #[should_panic]
+    #[case("", "")]
+    #[should_panic]
+    #[case("transfer/channel-1", "")]
+    #[should_panic]
+    #[case("transfer/channel-1/transfer/channel-2", "")]
+    fn test_strange_prefixed_denom(#[case] prefix: &str, #[case] denom: &str) {
+        let pd_s = if prefix.is_empty() {
+            denom.to_owned()
+        } else {
+            format!("{}/{}", prefix, denom)
+        };
+        let pd = PrefixedDenom::from_str(&pd_s).expect("no error");
 
         assert_eq!(pd.trace_path.to_string(), prefix);
         assert_eq!(pd.base_denom.to_string(), denom);
-
-        Ok(())
     }
 
     #[test]

From a9b8d8b7763546541238a168fb1e6e6703b9fa61 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 21:31:37 +0200
Subject: [PATCH 11/50] use valid connection id

---
 ibc-testkit/src/fixtures/core/connection/conn_open_confirm.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ibc-testkit/src/fixtures/core/connection/conn_open_confirm.rs b/ibc-testkit/src/fixtures/core/connection/conn_open_confirm.rs
index 151ab7e37..9a5014b87 100644
--- a/ibc-testkit/src/fixtures/core/connection/conn_open_confirm.rs
+++ b/ibc-testkit/src/fixtures/core/connection/conn_open_confirm.rs
@@ -14,7 +14,7 @@ pub fn dummy_conn_open_confirm() -> MsgConnectionOpenConfirm {
 /// Returns a dummy `RawMsgConnectionOpenConfirm` for testing purposes only!
 pub fn dummy_raw_msg_conn_open_confirm() -> RawMsgConnectionOpenConfirm {
     RawMsgConnectionOpenConfirm {
-        connection_id: "srcconnection".to_string(),
+        connection_id: "connection-118".to_string(),
         proof_ack: dummy_proof(),
         proof_height: Some(Height {
             revision_number: 0,

From 6542a23281af59303540025cfe7deb0f54951f91 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 21:48:07 +0200
Subject: [PATCH 12/50] failing doc tests

---
 ibc-core/ics24-host/types/src/identifiers/channel_id.rs    | 4 ++--
 ibc-core/ics24-host/types/src/identifiers/connection_id.rs | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/ibc-core/ics24-host/types/src/identifiers/channel_id.rs b/ibc-core/ics24-host/types/src/identifiers/channel_id.rs
index 5d4583dc6..c8f9e30d7 100644
--- a/ibc-core/ics24-host/types/src/identifiers/channel_id.rs
+++ b/ibc-core/ics24-host/types/src/identifiers/channel_id.rs
@@ -88,9 +88,9 @@ impl AsRef<str> for ChannelId {
 /// ```
 /// use core::str::FromStr;
 /// use ibc_core_host_types::identifiers::ChannelId;
-/// let channel_id = ChannelId::from_str("channelId-0");
+/// let channel_id = ChannelId::from_str("channel-0");
 /// assert!(channel_id.is_ok());
-/// channel_id.map(|id| {assert_eq!(&id, "channelId-0")});
+/// channel_id.map(|id| {assert_eq!(&id, "channel-0")});
 /// ```
 impl PartialEq<str> for ChannelId {
     fn eq(&self, other: &str) -> bool {
diff --git a/ibc-core/ics24-host/types/src/identifiers/connection_id.rs b/ibc-core/ics24-host/types/src/identifiers/connection_id.rs
index 883c41138..9fe9657cc 100644
--- a/ibc-core/ics24-host/types/src/identifiers/connection_id.rs
+++ b/ibc-core/ics24-host/types/src/identifiers/connection_id.rs
@@ -82,9 +82,9 @@ impl FromStr for ConnectionId {
 /// ```
 /// use core::str::FromStr;
 /// use ibc_core_host_types::identifiers::ConnectionId;
-/// let conn_id = ConnectionId::from_str("connectionId-0");
+/// let conn_id = ConnectionId::from_str("connection-0");
 /// assert!(conn_id.is_ok());
-/// conn_id.map(|id| {assert_eq!(&id, "connectionId-0")});
+/// conn_id.map(|id| {assert_eq!(&id, "connection-0")});
 /// ```
 impl PartialEq<str> for ConnectionId {
     fn eq(&self, other: &str) -> bool {

From 3337f6591e5321ebdfe44be480627271537368db Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 21:48:20 +0200
Subject: [PATCH 13/50] use existing constants

---
 ibc-core/ics24-host/types/src/validate.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/ibc-core/ics24-host/types/src/validate.rs b/ibc-core/ics24-host/types/src/validate.rs
index b800c1d3b..09685c091 100644
--- a/ibc-core/ics24-host/types/src/validate.rs
+++ b/ibc-core/ics24-host/types/src/validate.rs
@@ -1,6 +1,7 @@
 use ibc_primitives::prelude::*;
 
 use crate::error::IdentifierError as Error;
+use crate::identifiers::{ChannelId, ConnectionId};
 
 const VALID_SPECIAL_CHARS: &str = "._+-#[]<>";
 
@@ -115,7 +116,7 @@ pub fn validate_client_identifier(id: &str) -> Result<(), Error> {
 pub fn validate_connection_identifier(id: &str) -> Result<(), Error> {
     validate_identifier_chars(id)?;
     validate_identifier_length(id, 10, 64)?;
-    validate_named_u64_index(id, "connection")?;
+    validate_named_u64_index(id, ConnectionId::prefix())?;
     Ok(())
 }
 
@@ -135,7 +136,7 @@ pub fn validate_port_identifier(id: &str) -> Result<(), Error> {
 pub fn validate_channel_identifier(id: &str) -> Result<(), Error> {
     validate_identifier_chars(id)?;
     validate_identifier_length(id, 8, 64)?;
-    validate_named_u64_index(id, "channel")?;
+    validate_named_u64_index(id, ChannelId::prefix())?;
     Ok(())
 }
 

From a88e1d27ad67690ee96b69d1ee30bac6b7ef7e67 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 21:51:20 +0200
Subject: [PATCH 14/50] changelog entry

---
 .../unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md     | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 .changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md

diff --git a/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md b/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md
new file mode 100644
index 000000000..f081bfe6d
--- /dev/null
+++ b/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md
@@ -0,0 +1,2 @@
+- [ibc-apps-transfer] Compatible `PrefixedDenom` parsing with `ibc-go`.
+  ([\#1177](https://github.com/cosmos/ibc-rs/issues/1177))

From dd021d9c7ebf05831039697665780839b0a843f3 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 19 Apr 2024 22:04:51 +0200
Subject: [PATCH 15/50] refactor tests

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 31 +++++++++++++++-------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 42223a7f1..26ea9a360 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -450,22 +450,35 @@ mod tests {
     #[case("", "transfer/channel-1")]
     #[case("transfer/channel-1", "transfer")]
     #[case("", "transfer/channelToA/uatom")]
-    #[should_panic]
-    #[case("", "")]
-    #[should_panic]
-    #[case("transfer/channel-1", "")]
-    #[should_panic]
-    #[case("transfer/channel-1/transfer/channel-2", "")]
-    fn test_strange_prefixed_denom(#[case] prefix: &str, #[case] denom: &str) {
+    fn test_strange_but_accepted_prefixed_denom(
+        #[case] prefix: &str,
+        #[case] denom: &str,
+    ) -> Result<(), TokenTransferError> {
         let pd_s = if prefix.is_empty() {
             denom.to_owned()
         } else {
-            format!("{}/{}", prefix, denom)
+            format!("{prefix}/{denom}")
         };
-        let pd = PrefixedDenom::from_str(&pd_s).expect("no error");
+        let pd = PrefixedDenom::from_str(&pd_s)?;
 
         assert_eq!(pd.trace_path.to_string(), prefix);
         assert_eq!(pd.base_denom.to_string(), denom);
+
+        Ok(())
+    }
+
+    #[rstest]
+    #[case("")]
+    #[case("transfer/channel-1")]
+    #[case("transfer/channel-1/transfer/channel-2")]
+    #[should_panic(expected = "EmptyBaseDenom")]
+    fn test_prefixed_empty_base_denom(#[case] prefix: &str) {
+        let pd_s = if prefix.is_empty() {
+            "".to_owned()
+        } else {
+            format!("{prefix}/")
+        };
+        PrefixedDenom::from_str(&pd_s).expect("error");
     }
 
     #[test]

From 4a7c0347ff8039d33e325f8c5ad882c559c99f55 Mon Sep 17 00:00:00 2001
From: Rano | Ranadeep <ranadeep@informal.systems>
Date: Sat, 20 Apr 2024 04:38:33 -0400
Subject: [PATCH 16/50] apply suggestions from code review

Co-authored-by: Sean Chen <seanchen11235@gmail.com>
Co-authored-by: Farhad Shabani <Farhad.Shabani@gmail.com>
Signed-off-by: Rano | Ranadeep <ranadip.bswas@gmail.com>
---
 .../unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md   | 2 +-
 ibc-core/ics24-host/types/src/validate.rs                     | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md b/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md
index f081bfe6d..c7dd829c3 100644
--- a/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md
+++ b/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md
@@ -1,2 +1,2 @@
-- [ibc-apps-transfer] Compatible `PrefixedDenom` parsing with `ibc-go`.
+- [ibc-apps-transfer] Bring `PrefixedDenom` parsing up to parity with `ibc-go`.
   ([\#1177](https://github.com/cosmos/ibc-rs/issues/1177))
diff --git a/ibc-core/ics24-host/types/src/validate.rs b/ibc-core/ics24-host/types/src/validate.rs
index 09685c091..7286bbc05 100644
--- a/ibc-core/ics24-host/types/src/validate.rs
+++ b/ibc-core/ics24-host/types/src/validate.rs
@@ -187,7 +187,7 @@ mod tests {
     }
 
     #[test]
-    fn parse_invalid_connection_id_non_idexed() {
+    fn parse_invalid_connection_id_non_indexed() {
         // invalid indexing for connection id
         validate_connection_identifier("connection-0123").expect_err("InvalidNamedIndex");
         validate_connection_identifier("connection0123").expect_err("InvalidNamedIndex");
@@ -222,7 +222,7 @@ mod tests {
     }
 
     #[test]
-    fn parse_invalid_channel_id_non_idexed() {
+    fn parse_invalid_channel_id_non_indexed() {
         // invalid indexing for channel id
         validate_channel_identifier("channel-0123").expect_err("InvalidNamedIndex");
         validate_channel_identifier("channel0123").expect_err("InvalidNamedIndex");

From 9d246d43d3306990010efc63253d513cdee43b0c Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Sat, 20 Apr 2024 10:54:17 +0200
Subject: [PATCH 17/50] add comment for PrefixedDenom::from_str

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 26ea9a360..b3cd44ebf 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -300,6 +300,27 @@ pub fn is_receiver_chain_source(
 impl FromStr for PrefixedDenom {
     type Err = TokenTransferError;
 
+    /// Initializes a [`PrefixedDenom`] from a string that adheres to the format
+    /// `{port-id-1/channel-id-1}/{port-id-2/channel-id-2}/.../{port-id-n/channel-id-n}/base-denom`.
+    /// A [`PrefixedDenom`] exhibits a sequence of `{port-id/channel-id}` pairs.
+    /// This sequence makes up the [`TracePath`] of the [`PrefixedDenom`].
+    ///
+    /// This [`PrefixedDenom::from_str`] implementation _left-split-twice_ the argument string
+    /// using `/` delimiter. Then it peeks into the first two segments and attempts to convert
+    /// the first segment into a [`PortId`] and the second into a [`ChannelId`].
+    /// This continues on the third remaining segment in a loop until a
+    /// `{port-id/channel-id}` pair cannot be created from the top two segments.
+    /// The remaining parts of the string are then considered the `BaseDenom`.
+    ///
+    /// For example, given the following denom trace:
+    /// "transfer/channel-75/factory/stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4/dust",
+    /// the first two `/`-delimited segments are `"transfer"` and `"channel-75"`. The
+    /// first is a valid [`PortId`], and the second is a valid [`ChannelId`], so that becomes
+    /// the first `{port-id/channel-id}` pair that gets added as part of the [`TracePath`]
+    /// of the [`PrefixedDenom`]. The next two segments are `"factory"`, a
+    /// valid [`PortId`], and `"stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4"`, and invalid `ChannelId`.
+    /// The loop breaks at this point, resulting in a [`TracePath`] of `"transfer/channel-75"`
+    /// and a [`BaseDenom`] of `"factory/stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4/dust"`.
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         let mut trace_prefixes = vec![];
 

From be0f6935e6bf48d1a16faacc5f01aec8199a83d1 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Sat, 20 Apr 2024 11:00:29 +0200
Subject: [PATCH 18/50] rm TracePath::new

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index b3cd44ebf..f10506887 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -92,9 +92,10 @@ impl Display for TracePrefix {
 }
 
 /// A full trace path modelled as a collection of `TracePrefix`s.
-// Internally, the `TracePath` is modelled as a `Vec<TracePrefix>` but with the order reversed, i.e.
-// "transfer/channel-0/transfer/channel-1/uatom" => `["transfer/channel-1", "transfer/channel-0"]`
-// This is done for ease of addition/removal of prefixes.
+///
+/// Internally, the `TracePath` is modelled as a `Vec<TracePrefix>` but with the order reversed, i.e.
+/// "transfer/channel-0/transfer/channel-1/uatom" => `["transfer/channel-1", "transfer/channel-0"]`
+/// This is done for ease of addition/removal of prefixes.
 #[cfg_attr(
     feature = "parity-scale-codec",
     derive(
@@ -113,13 +114,6 @@ impl Display for TracePrefix {
 pub struct TracePath(Vec<TracePrefix>);
 
 impl TracePath {
-    /// Creates a new trace path from a vector of trace prefixes.
-    /// Reverse the order of the prefixes for easier addition/removal from the end.
-    pub fn new(mut trace: Vec<TracePrefix>) -> Self {
-        trace.reverse();
-        Self(trace)
-    }
-
     /// Returns true iff this path starts with the specified prefix
     pub fn starts_with(&self, prefix: &TracePrefix) -> bool {
         self.0.last().map(|p| p == prefix).unwrap_or(false)
@@ -348,7 +342,11 @@ impl FromStr for PrefixedDenom {
             }
         }
 
-        let trace_path = TracePath::new(trace_prefixes);
+        // reversing is needed, as [`TracePath`] requires quick addition/removal
+        // of prefixes which is performant from the end of a [`Vec`].
+        trace_prefixes.reverse();
+        let trace_path = TracePath::from(trace_prefixes);
+
         let base_denom = BaseDenom::from_str(remaining_parts)?;
 
         Ok(Self {

From 02d57c81abab55182fa999abd0879130626767f3 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Sat, 20 Apr 2024 11:05:48 +0200
Subject: [PATCH 19/50] collect the same tests

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 24 ++--------------------
 1 file changed, 2 insertions(+), 22 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index f10506887..3b1c4f320 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -446,6 +446,8 @@ mod tests {
         "transfer/channel-75/transfer/channel-123/transfer/channel-1023/transfer/channel-0",
         "//////////////////////dust"
     )]
+    #[case("transfer/channel-0", "uatom")]
+    #[case("transfer/channel-0/transfer/channel-1", "uatom")]
     // https://github.com/cosmos/ibc-go/blob/e2ad31975f2ede592912b86346b5ebf055c9e05f/modules/apps/transfer/types/trace_test.go#L17-L38
     #[case("", "uatom")]
     #[case("", "uatom/")]
@@ -500,28 +502,6 @@ mod tests {
         PrefixedDenom::from_str(&pd_s).expect("error");
     }
 
-    #[test]
-    fn test_denom_trace() -> Result<(), TokenTransferError> {
-        assert_eq!(
-            PrefixedDenom::from_str("transfer/channel-0/uatom")?,
-            PrefixedDenom {
-                trace_path: "transfer/channel-0".parse()?,
-                base_denom: "uatom".parse()?
-            },
-            "valid single trace info"
-        );
-        assert_eq!(
-            PrefixedDenom::from_str("transfer/channel-0/transfer/channel-1/uatom")?,
-            PrefixedDenom {
-                trace_path: "transfer/channel-0/transfer/channel-1".parse()?,
-                base_denom: "uatom".parse()?
-            },
-            "valid multiple trace info"
-        );
-
-        Ok(())
-    }
-
     #[test]
     fn test_denom_serde() -> Result<(), TokenTransferError> {
         let dt_str = "transfer/channel-0/uatom";

From b1804b036d5a8915ea7ef734e5e022a48dfb66f1 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Sat, 20 Apr 2024 11:06:38 +0200
Subject: [PATCH 20/50] test parsed PrefixedDenom string repr

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 3b1c4f320..870658396 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -482,6 +482,7 @@ mod tests {
         };
         let pd = PrefixedDenom::from_str(&pd_s)?;
 
+        assert_eq!(pd.to_string(), pd_s);
         assert_eq!(pd.trace_path.to_string(), prefix);
         assert_eq!(pd.base_denom.to_string(), denom);
 
@@ -502,19 +503,6 @@ mod tests {
         PrefixedDenom::from_str(&pd_s).expect("error");
     }
 
-    #[test]
-    fn test_denom_serde() -> Result<(), TokenTransferError> {
-        let dt_str = "transfer/channel-0/uatom";
-        let dt = PrefixedDenom::from_str(dt_str)?;
-        assert_eq!(dt.to_string(), dt_str, "valid single trace info");
-
-        let dt_str = "transfer/channel-0/transfer/channel-1/uatom";
-        let dt = PrefixedDenom::from_str(dt_str)?;
-        assert_eq!(dt.to_string(), dt_str, "valid multiple trace info");
-
-        Ok(())
-    }
-
     #[test]
     fn test_trace_path() -> Result<(), TokenTransferError> {
         assert!(TracePath::from_str("").is_ok(), "empty trace path");

From baedfb70edada2f910e4b5e2e93451219ad8c1d9 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Sat, 20 Apr 2024 11:24:45 +0200
Subject: [PATCH 21/50] test trace order

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 87 ++++++++++++++++++++++
 1 file changed, 87 insertions(+)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 870658396..216c7ee45 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -503,6 +503,93 @@ mod tests {
         PrefixedDenom::from_str(&pd_s).expect("error");
     }
 
+    #[rstest]
+    fn test_trace_path_order() {
+        let mut prefixed_denom =
+            PrefixedDenom::from_str("customtransfer/channel-1/alternativetransfer/channel-2/uatom")
+                .expect("no error");
+
+        assert_eq!(
+            prefixed_denom.trace_path.to_string(),
+            "customtransfer/channel-1/alternativetransfer/channel-2"
+        );
+        assert_eq!(prefixed_denom.base_denom.to_string(), "uatom");
+
+        let trace_prefix_1 = TracePrefix::new(
+            "alternativetransfer".parse().unwrap(),
+            "channel-2".parse().unwrap(),
+        );
+
+        let trace_prefix_2 = TracePrefix::new(
+            "customtransfer".parse().unwrap(),
+            "channel-1".parse().unwrap(),
+        );
+
+        let trace_prefix_3 =
+            TracePrefix::new("transferv2".parse().unwrap(), "channel-10".parse().unwrap());
+        let trace_prefix_4 = TracePrefix::new(
+            "transferv3".parse().unwrap(),
+            "channel-101".parse().unwrap(),
+        );
+
+        prefixed_denom.trace_path.add_prefix(trace_prefix_3.clone());
+
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_1));
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_2));
+        assert!(prefixed_denom.trace_path.starts_with(&trace_prefix_3));
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_4));
+
+        assert_eq!(
+            prefixed_denom.to_string(),
+            "transferv2/channel-10/customtransfer/channel-1/alternativetransfer/channel-2/uatom"
+        );
+
+        prefixed_denom.trace_path.remove_prefix(&trace_prefix_4);
+
+        assert!(!prefixed_denom.trace_path.is_empty());
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_1));
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_2));
+        assert!(prefixed_denom.trace_path.starts_with(&trace_prefix_3));
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_4));
+        assert_eq!(
+            prefixed_denom.to_string(),
+            "transferv2/channel-10/customtransfer/channel-1/alternativetransfer/channel-2/uatom"
+        );
+
+        prefixed_denom.trace_path.remove_prefix(&trace_prefix_3);
+
+        assert!(!prefixed_denom.trace_path.is_empty());
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_1));
+        assert!(prefixed_denom.trace_path.starts_with(&trace_prefix_2));
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_3));
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_4));
+        assert_eq!(
+            prefixed_denom.to_string(),
+            "customtransfer/channel-1/alternativetransfer/channel-2/uatom"
+        );
+
+        prefixed_denom.trace_path.remove_prefix(&trace_prefix_2);
+
+        assert!(!prefixed_denom.trace_path.is_empty());
+        assert!(prefixed_denom.trace_path.starts_with(&trace_prefix_1));
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_2));
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_3));
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_4));
+        assert_eq!(
+            prefixed_denom.to_string(),
+            "alternativetransfer/channel-2/uatom"
+        );
+
+        prefixed_denom.trace_path.remove_prefix(&trace_prefix_1);
+
+        assert!(prefixed_denom.trace_path.is_empty());
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_1));
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_2));
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_3));
+        assert!(!prefixed_denom.trace_path.starts_with(&trace_prefix_4));
+        assert_eq!(prefixed_denom.to_string(), "uatom");
+    }
+
     #[test]
     fn test_trace_path() -> Result<(), TokenTransferError> {
         assert!(TracePath::from_str("").is_ok(), "empty trace path");

From 32f54074427fdb26dbe6e6e3dcaa21e13d8c5d41 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Sat, 20 Apr 2024 11:30:21 +0200
Subject: [PATCH 22/50] more tests

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 216c7ee45..29b357aec 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -448,6 +448,9 @@ mod tests {
     )]
     #[case("transfer/channel-0", "uatom")]
     #[case("transfer/channel-0/transfer/channel-1", "uatom")]
+    #[case("", "/")]
+    #[case("", "transfer/uatom")]
+    #[case("", "transfer//uatom")]
     // https://github.com/cosmos/ibc-go/blob/e2ad31975f2ede592912b86346b5ebf055c9e05f/modules/apps/transfer/types/trace_test.go#L17-L38
     #[case("", "uatom")]
     #[case("", "uatom/")]

From e3c109b46d2dbd3b36da348bf0cb10cf02899846 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Sat, 20 Apr 2024 11:30:28 +0200
Subject: [PATCH 23/50] update tests

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 29b357aec..ae7d57b88 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -493,17 +493,13 @@ mod tests {
     }
 
     #[rstest]
+    #[case("transfer/channel-1/")]
+    #[case("transfer/channel-1/transfer/channel-2/")]
     #[case("")]
-    #[case("transfer/channel-1")]
-    #[case("transfer/channel-1/transfer/channel-2")]
+    #[case("transfer/channel-0/")]
     #[should_panic(expected = "EmptyBaseDenom")]
-    fn test_prefixed_empty_base_denom(#[case] prefix: &str) {
-        let pd_s = if prefix.is_empty() {
-            "".to_owned()
-        } else {
-            format!("{prefix}/")
-        };
-        PrefixedDenom::from_str(&pd_s).expect("error");
+    fn test_prefixed_empty_base_denom(#[case] pd_s: &str) {
+        PrefixedDenom::from_str(pd_s).expect("error");
     }
 
     #[rstest]

From dfe5a7c863e32c5bc9dc02a0300a7d792a39f231 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Sat, 20 Apr 2024 11:33:39 +0200
Subject: [PATCH 24/50] rm redundant error variant

---
 ibc-core/ics24-host/types/src/error.rs    |  2 --
 ibc-core/ics24-host/types/src/validate.rs | 20 ++++----------------
 2 files changed, 4 insertions(+), 18 deletions(-)

diff --git a/ibc-core/ics24-host/types/src/error.rs b/ibc-core/ics24-host/types/src/error.rs
index b0b6151e0..4df4c4dd9 100644
--- a/ibc-core/ics24-host/types/src/error.rs
+++ b/ibc-core/ics24-host/types/src/error.rs
@@ -16,8 +16,6 @@ pub enum IdentifierError {
     RevisionNumberOverflow,
     /// String `{value}` cannot be converted to packet sequence, error: `{reason}`
     InvalidStringAsSequence { value: String, reason: String },
-    /// String `{id}` does not start with `{name}`
-    InvalidNamedIndex { id: String, name: String },
 }
 
 #[cfg(feature = "std")]
diff --git a/ibc-core/ics24-host/types/src/validate.rs b/ibc-core/ics24-host/types/src/validate.rs
index 7286bbc05..3d607db0d 100644
--- a/ibc-core/ics24-host/types/src/validate.rs
+++ b/ibc-core/ics24-host/types/src/validate.rs
@@ -67,29 +67,17 @@ pub fn validate_prefix_length(
 pub fn validate_named_u64_index(id: &str, name: &str) -> Result<(), Error> {
     let number_s = id
         .strip_prefix(name)
-        .ok_or_else(|| Error::InvalidNamedIndex {
-            id: id.into(),
-            name: name.into(),
-        })?
+        .ok_or_else(|| Error::InvalidPrefix { prefix: id.into() })?
         .strip_prefix('-')
-        .ok_or_else(|| Error::InvalidNamedIndex {
-            id: id.into(),
-            name: name.into(),
-        })?;
+        .ok_or_else(|| Error::InvalidPrefix { prefix: id.into() })?;
 
     if number_s.starts_with('0') && number_s.len() > 1 {
-        return Err(Error::InvalidNamedIndex {
-            id: id.into(),
-            name: name.into(),
-        });
+        return Err(Error::InvalidPrefix { prefix: id.into() });
     }
 
     _ = number_s
         .parse::<u64>()
-        .map_err(|_| Error::InvalidNamedIndex {
-            id: id.into(),
-            name: name.into(),
-        })?;
+        .map_err(|_| Error::InvalidPrefix { prefix: id.into() })?;
 
     Ok(())
 }

From 5dd55593af8cd93008b0873121a3fa81499b1054 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Sat, 20 Apr 2024 11:37:55 +0200
Subject: [PATCH 25/50] refactor tests

---
 ibc-core/ics24-host/types/src/validate.rs | 29 +++++++++++------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/ibc-core/ics24-host/types/src/validate.rs b/ibc-core/ics24-host/types/src/validate.rs
index 3d607db0d..8346ff912 100644
--- a/ibc-core/ics24-host/types/src/validate.rs
+++ b/ibc-core/ics24-host/types/src/validate.rs
@@ -169,20 +169,19 @@ mod tests {
     #[test]
     fn parse_invalid_connection_id_indexed() {
         // valid connection id with index
-        validate_connection_identifier("connection-0").expect("no error");
-        validate_connection_identifier("connection-123").expect("no error");
-        validate_connection_identifier("connection-18446744073709551615").expect("no error");
+        validate_connection_identifier("connection-0").expect("success");
+        validate_connection_identifier("connection-123").expect("success");
+        validate_connection_identifier("connection-18446744073709551615").expect("success");
     }
 
     #[test]
     fn parse_invalid_connection_id_non_indexed() {
         // invalid indexing for connection id
-        validate_connection_identifier("connection-0123").expect_err("InvalidNamedIndex");
-        validate_connection_identifier("connection0123").expect_err("InvalidNamedIndex");
-        validate_connection_identifier("connection000").expect_err("InvalidNamedIndex");
+        validate_connection_identifier("connection-0123").expect_err("failure");
+        validate_connection_identifier("connection0123").expect_err("failure");
+        validate_connection_identifier("connection000").expect_err("failure");
         // 1 << 64 = 18446744073709551616
-        validate_connection_identifier("connection-18446744073709551616")
-            .expect_err("InvalidNamedIndex");
+        validate_connection_identifier("connection-18446744073709551616").expect_err("failure");
     }
 
     #[test]
@@ -204,19 +203,19 @@ mod tests {
     #[test]
     fn parse_invalid_channel_id_indexed() {
         // valid channel id with index
-        validate_channel_identifier("channel-0").expect("no error");
-        validate_channel_identifier("channel-123").expect("no error");
-        validate_channel_identifier("channel-18446744073709551615").expect("no error");
+        validate_channel_identifier("channel-0").expect("success");
+        validate_channel_identifier("channel-123").expect("success");
+        validate_channel_identifier("channel-18446744073709551615").expect("success");
     }
 
     #[test]
     fn parse_invalid_channel_id_non_indexed() {
         // invalid indexing for channel id
-        validate_channel_identifier("channel-0123").expect_err("InvalidNamedIndex");
-        validate_channel_identifier("channel0123").expect_err("InvalidNamedIndex");
-        validate_channel_identifier("channel000").expect_err("InvalidNamedIndex");
+        validate_channel_identifier("channel-0123").expect_err("failure");
+        validate_channel_identifier("channel0123").expect_err("failure");
+        validate_channel_identifier("channel000").expect_err("failure");
         // 1 << 64 = 18446744073709551616
-        validate_channel_identifier("channel-18446744073709551616").expect_err("InvalidNamedIndex");
+        validate_channel_identifier("channel-18446744073709551616").expect_err("failure");
     }
 
     #[test]

From 5d04ebf0ceb7fd2820af85f0578ac61f001bd5ea Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Sat, 20 Apr 2024 16:40:14 +0200
Subject: [PATCH 26/50] update doc string

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index ae7d57b88..ad5786880 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -304,7 +304,7 @@ impl FromStr for PrefixedDenom {
     /// the first segment into a [`PortId`] and the second into a [`ChannelId`].
     /// This continues on the third remaining segment in a loop until a
     /// `{port-id/channel-id}` pair cannot be created from the top two segments.
-    /// The remaining parts of the string are then considered the `BaseDenom`.
+    /// The remaining parts of the string are then considered the [`BaseDenom`].
     ///
     /// For example, given the following denom trace:
     /// "transfer/channel-75/factory/stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4/dust",
@@ -312,7 +312,7 @@ impl FromStr for PrefixedDenom {
     /// first is a valid [`PortId`], and the second is a valid [`ChannelId`], so that becomes
     /// the first `{port-id/channel-id}` pair that gets added as part of the [`TracePath`]
     /// of the [`PrefixedDenom`]. The next two segments are `"factory"`, a
-    /// valid [`PortId`], and `"stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4"`, and invalid `ChannelId`.
+    /// valid [`PortId`], and `"stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4"`, an invalid [`ChannelId`].
     /// The loop breaks at this point, resulting in a [`TracePath`] of `"transfer/channel-75"`
     /// and a [`BaseDenom`] of `"factory/stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4/dust"`.
     fn from_str(s: &str) -> Result<Self, Self::Err> {

From 50ebb2f2a6e0aa4ee673b1be1a69204be7820b84 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Sat, 20 Apr 2024 17:06:49 +0200
Subject: [PATCH 27/50] add comment on virtual split_twice

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index ad5786880..2318adef7 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -321,6 +321,8 @@ impl FromStr for PrefixedDenom {
         let mut remaining_parts = s;
 
         loop {
+            // The below two chained `split_once` calls emulate a virtual `split_twice` call,
+            // which is not available in the standard library.
             let parsed_prefix = remaining_parts
                 .split_once('/')
                 .and_then(|(port_id_s, remaining)| {

From 063c1df6da3646915407d8e992c94f85c278a972 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Sat, 20 Apr 2024 17:25:50 +0200
Subject: [PATCH 28/50] update doc str

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 2318adef7..5cfad00a8 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -295,8 +295,8 @@ impl FromStr for PrefixedDenom {
     type Err = TokenTransferError;
 
     /// Initializes a [`PrefixedDenom`] from a string that adheres to the format
-    /// `{port-id-1/channel-id-1}/{port-id-2/channel-id-2}/.../{port-id-n/channel-id-n}/base-denom`.
-    /// A [`PrefixedDenom`] exhibits a sequence of `{port-id/channel-id}` pairs.
+    /// `{1st-port-id/channel-<index>}/{2nd-port-id/channel-<index>}/.../{nth-port-id/channel-<index>}/<base_denom>`.
+    /// A [`PrefixedDenom`] exhibits a sequence of `{ith-port-id/channel-<index>}` pairs.
     /// This sequence makes up the [`TracePath`] of the [`PrefixedDenom`].
     ///
     /// This [`PrefixedDenom::from_str`] implementation _left-split-twice_ the argument string

From f72517ff1e078dd413fa103a73e8f14fe0d986c3 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Mon, 22 Apr 2024 14:55:43 +0200
Subject: [PATCH 29/50] add TracePrefix::strip and TracePath::trim

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 77 +++++++++++++---------
 1 file changed, 45 insertions(+), 32 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 5cfad00a8..ec3241e64 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -83,6 +83,26 @@ impl TracePrefix {
             channel_id,
         }
     }
+
+    /// Returns a string slice with [`TracePrefix`] removed.
+    ///
+    /// If the string starts a [`TracePrefix`] format, i.e. `{port-id}/channel-{id}/`,
+    /// it returns a tuple of the removed [`TracePrefix`] and the substring after the prefix.
+    ///
+    /// If the string does not start with a [`TracePrefix`], it returns `None`.
+    ///
+    /// It is analogous to `strip_prefix` from standard libray.
+    pub fn strip(s: &str) -> Option<(Self, &str)> {
+        // The below two chained `split_once` calls emulate a virtual `split_twice` call,
+        // which is not available in the standard library.
+        let (port_id_s, remaining) = s.split_once('/')?;
+        let (channel_id_s, remaining) = remaining.split_once('/')?;
+
+        let port_id = PortId::from_str(port_id_s).ok()?;
+        let channel_id = ChannelId::from_str(channel_id_s).ok()?;
+
+        Some((Self::new(port_id, channel_id), remaining))
+    }
 }
 
 impl Display for TracePrefix {
@@ -140,6 +160,30 @@ impl TracePath {
     pub fn empty() -> Self {
         Self(vec![])
     }
+
+    /// Returns a string slice with [`TracePath`] or all [`TracePrefix`]es repeatedly removed.
+    ///
+    /// If the string starts with a [`TracePath`], it returns a tuple of the removed
+    /// [`TracePath`] and the substring after the [`TracePath`].
+    ///
+    /// If the string does not have any [`TracePrefix`], it returns original string.
+    ///
+    /// It is analogous to `trim_start_matches` from standard library.
+    pub fn trim(s: &str) -> (Self, &str) {
+        let mut trace_prefixes = vec![];
+
+        let mut remaining_parts = s;
+
+        while let Some((trace_prefix, remaining)) = TracePrefix::strip(remaining_parts) {
+            trace_prefixes.push(trace_prefix);
+            remaining_parts = remaining;
+        }
+
+        // reversing is needed, as [`TracePath`] requires quick addition/removal
+        // of prefixes which is performant from the end of a [`Vec`].
+        trace_prefixes.reverse();
+        (Self(trace_prefixes), remaining_parts)
+    }
 }
 
 impl<'a> TryFrom<Vec<&'a str>> for TracePath {
@@ -316,38 +360,7 @@ impl FromStr for PrefixedDenom {
     /// The loop breaks at this point, resulting in a [`TracePath`] of `"transfer/channel-75"`
     /// and a [`BaseDenom`] of `"factory/stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4/dust"`.
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let mut trace_prefixes = vec![];
-
-        let mut remaining_parts = s;
-
-        loop {
-            // The below two chained `split_once` calls emulate a virtual `split_twice` call,
-            // which is not available in the standard library.
-            let parsed_prefix = remaining_parts
-                .split_once('/')
-                .and_then(|(port_id_s, remaining)| {
-                    remaining
-                        .split_once('/')
-                        .map(|(channel_id_s, remaining)| (port_id_s, channel_id_s, remaining))
-                })
-                .and_then(|(port_id_s, channel_id_s, remaining)| {
-                    let port_id = PortId::from_str(port_id_s).ok()?;
-                    let channel_id = ChannelId::from_str(channel_id_s).ok()?;
-                    Some((port_id, channel_id, remaining))
-                });
-            match parsed_prefix {
-                Some((port_id, channel_id, remaining)) => {
-                    trace_prefixes.push(TracePrefix::new(port_id, channel_id));
-                    remaining_parts = remaining;
-                }
-                None => break,
-            }
-        }
-
-        // reversing is needed, as [`TracePath`] requires quick addition/removal
-        // of prefixes which is performant from the end of a [`Vec`].
-        trace_prefixes.reverse();
-        let trace_path = TracePath::from(trace_prefixes);
+        let (trace_path, remaining_parts) = TracePath::trim(s);
 
         let base_denom = BaseDenom::from_str(remaining_parts)?;
 

From 25111df6139cde06aa6711d39da58df057ab8c6a Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Mon, 22 Apr 2024 14:57:39 +0200
Subject: [PATCH 30/50] add whitespace cases

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index ec3241e64..83be597e8 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -510,7 +510,9 @@ mod tests {
     #[rstest]
     #[case("transfer/channel-1/")]
     #[case("transfer/channel-1/transfer/channel-2/")]
+    #[case("transfer/channel-21/transfer/channel-23/  ")]
     #[case("")]
+    #[case("   ")]
     #[case("transfer/channel-0/")]
     #[should_panic(expected = "EmptyBaseDenom")]
     fn test_prefixed_empty_base_denom(#[case] pd_s: &str) {

From 76cf402c4592625ac27db27d45dd26744dc5ecbd Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Mon, 22 Apr 2024 15:03:46 +0200
Subject: [PATCH 31/50] refactor tests

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 48 +++++++++-------------
 1 file changed, 19 insertions(+), 29 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 83be597e8..9cbec93fa 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -418,34 +418,18 @@ mod tests {
 
     use super::*;
 
-    #[test]
-    fn test_denom_validation() -> Result<(), TokenTransferError> {
-        assert!(BaseDenom::from_str("").is_err(), "empty base denom");
-        assert!(BaseDenom::from_str("uatom").is_ok(), "valid base denom");
-        assert!(PrefixedDenom::from_str("").is_err(), "empty denom trace");
-        assert!(
-            PrefixedDenom::from_str("transfer/channel-0/").is_err(),
-            "empty base denom with trace"
-        );
-        assert!(
-            PrefixedDenom::from_str("transfer/channel-0/uatom").is_ok(),
-            "valid single trace info"
-        );
-        assert!(
-            PrefixedDenom::from_str("transfer/channel-0/transfer/channel-1/uatom").is_ok(),
-            "valid multiple trace info"
-        );
-
-        // the followings are valid denom according to `ibc-go`
-        // https://github.com/cosmos/ibc-go/blob/e2ad31975f2ede592912b86346b5ebf055c9e05f/modules/apps/transfer/types/trace_test.go#L17-L38
-        PrefixedDenom::from_str("/uatom").expect("no error");
-        PrefixedDenom::from_str("//uatom").expect("no error");
-        PrefixedDenom::from_str("transfer/").expect("no error");
-        PrefixedDenom::from_str("transfer/atom").expect("no error");
-        PrefixedDenom::from_str("(transfer)/channel-0/uatom").expect("no error");
-        PrefixedDenom::from_str("transfer/(channel-0)/uatom").expect("no error");
+    #[rstest]
+    #[case("uatom")]
+    #[case("atom")]
+    fn test_accepted_denom(#[case] denom_str: &str) {
+        BaseDenom::from_str(denom_str).expect("success");
+    }
 
-        Ok(())
+    #[rstest]
+    #[case("")]
+    #[case(" ")]
+    fn test_rejected_denom(#[case] denom_str: &str) {
+        BaseDenom::from_str(denom_str).expect_err("failure");
     }
 
     #[rstest]
@@ -465,7 +449,13 @@ mod tests {
     #[case("transfer/channel-0/transfer/channel-1", "uatom")]
     #[case("", "/")]
     #[case("", "transfer/uatom")]
+    #[case("", "transfer/atom")]
     #[case("", "transfer//uatom")]
+    #[case("", "/uatom")]
+    #[case("", "//uatom")]
+    #[case("", "transfer/")]
+    #[case("", "(transfer)/channel-0/uatom")]
+    #[case("", "transfer/(channel-0)/uatom")]
     // https://github.com/cosmos/ibc-go/blob/e2ad31975f2ede592912b86346b5ebf055c9e05f/modules/apps/transfer/types/trace_test.go#L17-L38
     #[case("", "uatom")]
     #[case("", "uatom/")]
@@ -508,11 +498,11 @@ mod tests {
     }
 
     #[rstest]
+    #[case("")]
+    #[case("   ")]
     #[case("transfer/channel-1/")]
     #[case("transfer/channel-1/transfer/channel-2/")]
     #[case("transfer/channel-21/transfer/channel-23/  ")]
-    #[case("")]
-    #[case("   ")]
     #[case("transfer/channel-0/")]
     #[should_panic(expected = "EmptyBaseDenom")]
     fn test_prefixed_empty_base_denom(#[case] pd_s: &str) {

From 1524a5088c9c7ccecdde91ee5bd4622eda94f786 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Mon, 22 Apr 2024 15:05:21 +0200
Subject: [PATCH 32/50] spelling

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 9cbec93fa..7a9dc44e4 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -91,7 +91,7 @@ impl TracePrefix {
     ///
     /// If the string does not start with a [`TracePrefix`], it returns `None`.
     ///
-    /// It is analogous to `strip_prefix` from standard libray.
+    /// It is analogous to `strip_prefix` from standard library.
     pub fn strip(s: &str) -> Option<(Self, &str)> {
         // The below two chained `split_once` calls emulate a virtual `split_twice` call,
         // which is not available in the standard library.

From 8720be03198541d43ae98ff7eca597789dafc580 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Mon, 22 Apr 2024 15:08:11 +0200
Subject: [PATCH 33/50] parse over from_str

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 7a9dc44e4..b089cf413 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -98,8 +98,8 @@ impl TracePrefix {
         let (port_id_s, remaining) = s.split_once('/')?;
         let (channel_id_s, remaining) = remaining.split_once('/')?;
 
-        let port_id = PortId::from_str(port_id_s).ok()?;
-        let channel_id = ChannelId::from_str(channel_id_s).ok()?;
+        let port_id = port_id_s.parse().ok()?;
+        let channel_id = channel_id_s.parse().ok()?;
 
         Some((Self::new(port_id, channel_id), remaining))
     }

From 93a81d5cf6b0e006bb23ae95436dc1c4a4f48f22 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Mon, 22 Apr 2024 15:11:58 +0200
Subject: [PATCH 34/50] nit

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index b089cf413..943c3f71a 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -171,7 +171,6 @@ impl TracePath {
     /// It is analogous to `trim_start_matches` from standard library.
     pub fn trim(s: &str) -> (Self, &str) {
         let mut trace_prefixes = vec![];
-
         let mut remaining_parts = s;
 
         while let Some((trace_prefix, remaining)) = TracePrefix::strip(remaining_parts) {

From 94ac9417379bbe5db9b9ac011ecbf066aad4d655 Mon Sep 17 00:00:00 2001
From: Rano | Ranadeep <ranadeep@informal.systems>
Date: Mon, 22 Apr 2024 10:05:56 -0400
Subject: [PATCH 35/50] apply suggestions from code review

Co-authored-by: Sean Chen <seanchen11235@gmail.com>
Signed-off-by: Rano | Ranadeep <ranadip.bswas@gmail.com>
---
 ibc-apps/ics20-transfer/types/src/denom.rs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 943c3f71a..c6caebc19 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -86,12 +86,12 @@ impl TracePrefix {
 
     /// Returns a string slice with [`TracePrefix`] removed.
     ///
-    /// If the string starts a [`TracePrefix`] format, i.e. `{port-id}/channel-{id}/`,
+    /// If the string starts with a [`TracePrefix`], i.e. `{port-id}/channel-{id}/`,
     /// it returns a tuple of the removed [`TracePrefix`] and the substring after the prefix.
     ///
-    /// If the string does not start with a [`TracePrefix`], it returns `None`.
+    /// If the string does not start with a [`TracePrefix`], this method returns `None`.
     ///
-    /// It is analogous to `strip_prefix` from standard library.
+    /// This method is analogous to `strip_prefix` from the standard library.
     pub fn strip(s: &str) -> Option<(Self, &str)> {
         // The below two chained `split_once` calls emulate a virtual `split_twice` call,
         // which is not available in the standard library.
@@ -166,9 +166,9 @@ impl TracePath {
     /// If the string starts with a [`TracePath`], it returns a tuple of the removed
     /// [`TracePath`] and the substring after the [`TracePath`].
     ///
-    /// If the string does not have any [`TracePrefix`], it returns original string.
+    /// If the string does not contain any [`TracePrefix`], it returns the original string.
     ///
-    /// It is analogous to `trim_start_matches` from standard library.
+    /// This method is analogous to `trim_start_matches` from the standard library.
     pub fn trim(s: &str) -> (Self, &str) {
         let mut trace_prefixes = vec![];
         let mut remaining_parts = s;
@@ -179,7 +179,7 @@ impl TracePath {
         }
 
         // reversing is needed, as [`TracePath`] requires quick addition/removal
-        // of prefixes which is performant from the end of a [`Vec`].
+        // of prefixes which is more performant from the end of a [`Vec`].
         trace_prefixes.reverse();
         (Self(trace_prefixes), remaining_parts)
     }

From 7408994c1f08b255b08c24c63c1435f363aac3ef Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Wed, 24 Apr 2024 14:24:16 +0200
Subject: [PATCH 36/50] add failing test

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index c6caebc19..726387200 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -196,6 +196,7 @@ impl<'a> TryFrom<Vec<&'a str>> for TracePath {
         }
 
         let mut trace = vec![];
+        // this does not take care of the remainder if the length is not even
         let id_pairs = v.chunks_exact(2).map(|paths| (paths[0], paths[1]));
         for (pos, (port_id, channel_id)) in id_pairs.rev().enumerate() {
             let port_id =
@@ -417,6 +418,19 @@ mod tests {
 
     use super::*;
 
+    #[rstest]
+    #[case("")]
+    #[case("transfer")]
+    #[case("transfer/channel-1/ica")]
+    fn test_invalid_raw_demon_trace_parsing(#[case] trace_path: &str) {
+        let raw_denom_trace = RawDenomTrace {
+            path: trace_path.to_string(),
+            base_denom: "uatom".to_string(),
+        };
+
+        PrefixedDenom::try_from(raw_denom_trace).expect("failure");
+    }
+
     #[rstest]
     #[case("uatom")]
     #[case("atom")]

From d34d9466071b9b67bdd800a0c157776762eff4a5 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Wed, 24 Apr 2024 14:29:27 +0200
Subject: [PATCH 37/50] fix TracePath::from_str

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 49 +++-------------------
 ibc-apps/ics20-transfer/types/src/error.rs |  2 +
 2 files changed, 7 insertions(+), 44 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 726387200..742ad137b 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -185,54 +185,15 @@ impl TracePath {
     }
 }
 
-impl<'a> TryFrom<Vec<&'a str>> for TracePath {
-    type Error = TokenTransferError;
-
-    fn try_from(v: Vec<&'a str>) -> Result<Self, Self::Error> {
-        if v.len() % 2 != 0 {
-            return Err(TokenTransferError::InvalidTraceLength {
-                len: v.len() as u64,
-            });
-        }
-
-        let mut trace = vec![];
-        // this does not take care of the remainder if the length is not even
-        let id_pairs = v.chunks_exact(2).map(|paths| (paths[0], paths[1]));
-        for (pos, (port_id, channel_id)) in id_pairs.rev().enumerate() {
-            let port_id =
-                PortId::from_str(port_id).map_err(|e| TokenTransferError::InvalidTracePortId {
-                    pos: pos as u64,
-                    validation_error: e,
-                })?;
-            let channel_id = ChannelId::from_str(channel_id).map_err(|e| {
-                TokenTransferError::InvalidTraceChannelId {
-                    pos: pos as u64,
-                    validation_error: e,
-                }
-            })?;
-            trace.push(TracePrefix {
-                port_id,
-                channel_id,
-            });
-        }
-
-        Ok(trace.into())
-    }
-}
-
 impl FromStr for TracePath {
     type Err = TokenTransferError;
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let parts = {
-            let parts: Vec<&str> = s.split('/').collect();
-            if parts.len() == 1 && parts[0].trim().is_empty() {
-                vec![]
-            } else {
-                parts
-            }
-        };
-        parts.try_into()
+        let (trace_path, remaining_parts) = TracePath::trim(s);
+        remaining_parts
+            .is_empty()
+            .then_some(trace_path)
+            .ok_or_else(|| TokenTransferError::MalformedTrace(s.to_string()))
     }
 }
 
diff --git a/ibc-apps/ics20-transfer/types/src/error.rs b/ibc-apps/ics20-transfer/types/src/error.rs
index 257fbc29d..7bd938408 100644
--- a/ibc-apps/ics20-transfer/types/src/error.rs
+++ b/ibc-apps/ics20-transfer/types/src/error.rs
@@ -39,6 +39,8 @@ pub enum TokenTransferError {
         pos: u64,
         validation_error: IdentifierError,
     },
+    /// malformed trace: `{0}`
+    MalformedTrace(String),
     /// trace length must be even but got: `{len}`
     InvalidTraceLength { len: u64 },
     /// invalid amount error: `{0}`

From 03b08d7bfdffab5e8b3162aac2320c26f3140ce1 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Wed, 24 Apr 2024 14:36:09 +0200
Subject: [PATCH 38/50] fix parsing

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 742ad137b..a8baf5431 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -189,7 +189,14 @@ impl FromStr for TracePath {
     type Err = TokenTransferError;
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let (trace_path, remaining_parts) = TracePath::trim(s);
+        if s.is_empty() {
+            return Ok(TracePath::empty());
+        }
+
+        // This is needed as TracePath trims `{port-id}/{channel-id}/`.
+        let slashed_s = format!("{}/", s);
+
+        let (trace_path, remaining_parts) = TracePath::trim(slashed_s.as_str());
         remaining_parts
             .is_empty()
             .then_some(trace_path)

From 29be17b032f2c1968493a0e8831a8e2aa52116ed Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Wed, 24 Apr 2024 14:57:51 +0200
Subject: [PATCH 39/50] fix test

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index a8baf5431..b6a85dd2d 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -387,7 +387,6 @@ mod tests {
     use super::*;
 
     #[rstest]
-    #[case("")]
     #[case("transfer")]
     #[case("transfer/channel-1/ica")]
     fn test_invalid_raw_demon_trace_parsing(#[case] trace_path: &str) {
@@ -396,7 +395,7 @@ mod tests {
             base_denom: "uatom".to_string(),
         };
 
-        PrefixedDenom::try_from(raw_denom_trace).expect("failure");
+        PrefixedDenom::try_from(raw_denom_trace).expect_err("failure");
     }
 
     #[rstest]

From 2b117335ebfe31421c47a25521884771bc69bf2d Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Wed, 24 Apr 2024 14:59:38 +0200
Subject: [PATCH 40/50] add ibc-app-transfer-types dep

---
 ibc-apps/ics721-nft-transfer/types/Cargo.toml | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/ibc-apps/ics721-nft-transfer/types/Cargo.toml b/ibc-apps/ics721-nft-transfer/types/Cargo.toml
index 9deb1a361..8ec4134b4 100644
--- a/ibc-apps/ics721-nft-transfer/types/Cargo.toml
+++ b/ibc-apps/ics721-nft-transfer/types/Cargo.toml
@@ -30,8 +30,9 @@ serde           = { workspace = true, optional = true }
 serde_json      = { workspace = true }
 
 # ibc dependencies
-ibc-core  = { workspace = true }
-ibc-proto = { workspace = true }
+ibc-core               = { workspace = true }
+ibc-proto              = { workspace = true }
+ibc-app-transfer-types = { workspace = true }
 
 ## parity dependencies
 parity-scale-codec = { workspace = true , optional = true }
@@ -50,27 +51,32 @@ std = [
     "http/std",
     "ibc-core/std",
     "ibc-proto/std",
+    "ibc-app-transfer-types/std",
 ]
 serde = [
     "dep:serde",
     "ibc-core/serde",
     "ibc-proto/serde",
+    "ibc-app-transfer-types/serde",
 ]
 schema = [
     "dep:schemars",
     "ibc-core/schema",
     "ibc-proto/json-schema",
     "serde",
-    "std"
+    "std",
+    "ibc-app-transfer-types/schema",
 ]
 borsh = [
     "dep:borsh",
     "ibc-core/borsh",
-    "ibc-proto/borsh"
+    "ibc-proto/borsh",
+    "ibc-app-transfer-types/borsh",
 ]
 parity-scale-codec = [
     "dep:parity-scale-codec",
     "dep:scale-info",
     "ibc-core/parity-scale-codec",
-    "ibc-proto/parity-scale-codec"
+    "ibc-proto/parity-scale-codec",
+    "ibc-app-transfer-types/parity-scale-codec",
 ]

From 1eecc2b5be4a2f7a1e740cab4e23843a94ef5eea Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Wed, 24 Apr 2024 15:00:07 +0200
Subject: [PATCH 41/50] rm reusable code

---
 .../ics721-nft-transfer/types/src/class.rs    | 148 +-----------------
 1 file changed, 1 insertion(+), 147 deletions(-)

diff --git a/ibc-apps/ics721-nft-transfer/types/src/class.rs b/ibc-apps/ics721-nft-transfer/types/src/class.rs
index c2ff9afd4..8f5ccd1da 100644
--- a/ibc-apps/ics721-nft-transfer/types/src/class.rs
+++ b/ibc-apps/ics721-nft-transfer/types/src/class.rs
@@ -2,8 +2,8 @@
 use core::fmt::{self, Display, Error as FmtError, Formatter};
 use core::str::FromStr;
 
-use derive_more::From;
 use http::Uri;
+pub use ibc_app_transfer_types::{TracePath, TracePrefix};
 use ibc_core::host::types::identifiers::{ChannelId, PortId};
 use ibc_core::primitives::prelude::*;
 #[cfg(feature = "serde")]
@@ -55,152 +55,6 @@ impl FromStr for ClassId {
     }
 }
 
-/// Class prefix, the same as ICS-20 TracePrefix
-#[cfg_attr(
-    feature = "parity-scale-codec",
-    derive(
-        parity_scale_codec::Encode,
-        parity_scale_codec::Decode,
-        scale_info::TypeInfo
-    )
-)]
-#[cfg_attr(
-    feature = "borsh",
-    derive(borsh::BorshSerialize, borsh::BorshDeserialize)
-)]
-#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
-#[cfg_attr(feature = "schema", derive(schemars::JsonSchema))]
-#[derive(Clone, Debug, Ord, PartialOrd, Eq, PartialEq)]
-pub struct TracePrefix {
-    port_id: PortId,
-    channel_id: ChannelId,
-}
-
-impl TracePrefix {
-    pub fn new(port_id: PortId, channel_id: ChannelId) -> Self {
-        Self {
-            port_id,
-            channel_id,
-        }
-    }
-}
-
-impl Display for TracePrefix {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), FmtError> {
-        write!(f, "{}/{}", self.port_id, self.channel_id)
-    }
-}
-
-/// Class trace path, the same as ICS-20 TracePath
-#[cfg_attr(
-    feature = "parity-scale-codec",
-    derive(
-        parity_scale_codec::Encode,
-        parity_scale_codec::Decode,
-        scale_info::TypeInfo
-    )
-)]
-#[cfg_attr(
-    feature = "borsh",
-    derive(borsh::BorshSerialize, borsh::BorshDeserialize)
-)]
-#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
-#[cfg_attr(feature = "schema", derive(schemars::JsonSchema))]
-#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, From)]
-pub struct TracePath(Vec<TracePrefix>);
-
-impl TracePath {
-    /// Returns true iff this path starts with the specified prefix
-    pub fn starts_with(&self, prefix: &TracePrefix) -> bool {
-        self.0.last().map(|p| p == prefix).unwrap_or(false)
-    }
-
-    /// Removes the specified prefix from the path if there is a match, otherwise does nothing.
-    pub fn remove_prefix(&mut self, prefix: &TracePrefix) {
-        if self.starts_with(prefix) {
-            self.0.pop();
-        }
-    }
-
-    /// Adds the specified prefix to the path.
-    pub fn add_prefix(&mut self, prefix: TracePrefix) {
-        self.0.push(prefix)
-    }
-
-    /// Returns true if the path is empty and false otherwise.
-    pub fn is_empty(&self) -> bool {
-        self.0.is_empty()
-    }
-
-    /// Return empty trace path
-    pub fn empty() -> Self {
-        Self(vec![])
-    }
-}
-
-impl<'a> TryFrom<Vec<&'a str>> for TracePath {
-    type Error = NftTransferError;
-
-    fn try_from(v: Vec<&'a str>) -> Result<Self, Self::Error> {
-        if v.len() % 2 != 0 {
-            return Err(NftTransferError::InvalidTraceLength {
-                len: v.len() as u64,
-            });
-        }
-
-        let mut trace = vec![];
-        let id_pairs = v.chunks_exact(2).map(|paths| (paths[0], paths[1]));
-        for (pos, (port_id, channel_id)) in id_pairs.rev().enumerate() {
-            let port_id =
-                PortId::from_str(port_id).map_err(|e| NftTransferError::InvalidTracePortId {
-                    pos: pos as u64,
-                    validation_error: e,
-                })?;
-            let channel_id = ChannelId::from_str(channel_id).map_err(|e| {
-                NftTransferError::InvalidTraceChannelId {
-                    pos: pos as u64,
-                    validation_error: e,
-                }
-            })?;
-            trace.push(TracePrefix {
-                port_id,
-                channel_id,
-            });
-        }
-
-        Ok(trace.into())
-    }
-}
-
-impl FromStr for TracePath {
-    type Err = NftTransferError;
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let parts = {
-            let parts: Vec<&str> = s.split('/').collect();
-            if parts.len() == 1 && parts[0].trim().is_empty() {
-                vec![]
-            } else {
-                parts
-            }
-        };
-        parts.try_into()
-    }
-}
-
-impl Display for TracePath {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), FmtError> {
-        let path = self
-            .0
-            .iter()
-            .rev()
-            .map(|prefix| prefix.to_string())
-            .collect::<Vec<String>>()
-            .join("/");
-        write!(f, "{path}")
-    }
-}
-
 /// Prefixed class to trace sources like ICS-20 PrefixedDenom
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 #[cfg_attr(feature = "schema", derive(schemars::JsonSchema))]

From 6ff2abf56123a29cbc76f0b2508abd21fc38948d Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Wed, 24 Apr 2024 15:01:25 +0200
Subject: [PATCH 42/50] update impls

---
 .../ics721-nft-transfer/types/src/class.rs    | 23 ++++++++-----------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/ibc-apps/ics721-nft-transfer/types/src/class.rs b/ibc-apps/ics721-nft-transfer/types/src/class.rs
index 8f5ccd1da..845e2d36a 100644
--- a/ibc-apps/ics721-nft-transfer/types/src/class.rs
+++ b/ibc-apps/ics721-nft-transfer/types/src/class.rs
@@ -121,19 +121,12 @@ pub fn is_receiver_chain_source(
 impl FromStr for PrefixedClassId {
     type Err = NftTransferError;
 
+    /// The parsing logic is same as [`FromStr`] impl of
+    /// [`PrefixedDenom`](ibc_app_transfer_types::PrefixedDenom) from ICS-20.
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let mut parts: Vec<&str> = s.split('/').collect();
-        let last_part = parts.pop().expect("split() returned an empty iterator");
-
-        let (base_class_id, trace_path) = {
-            if last_part == s {
-                (ClassId::from_str(s)?, TracePath::empty())
-            } else {
-                let base_class_id = ClassId::from_str(last_part)?;
-                let trace_path = TracePath::try_from(parts)?;
-                (base_class_id, trace_path)
-            }
-        };
+        let (trace_path, remaining_parts) = TracePath::trim(s);
+
+        let base_class_id = ClassId::from_str(remaining_parts)?;
 
         Ok(Self {
             trace_path,
@@ -147,7 +140,9 @@ impl TryFrom<RawClassTrace> for PrefixedClassId {
 
     fn try_from(value: RawClassTrace) -> Result<Self, Self::Error> {
         let base_class_id = ClassId::from_str(&value.base_class_id)?;
-        let trace_path = TracePath::from_str(&value.path)?;
+        // FIXME: separate `TracePath` error.
+        let trace_path = TracePath::from_str(&value.path)
+            .map_err(|err| NftTransferError::Other(err.to_string()))?;
         Ok(Self {
             trace_path,
             base_class_id,
@@ -175,7 +170,7 @@ impl From<ClassId> for PrefixedClassId {
 
 impl Display for PrefixedClassId {
     fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), FmtError> {
-        if self.trace_path.0.is_empty() {
+        if self.trace_path.is_empty() {
             write!(f, "{}", self.base_class_id)
         } else {
             write!(f, "{}/{}", self.trace_path, self.base_class_id)

From bd7922ed63bb2d24bc8d9b8e9fca2ca57db3d5e7 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Wed, 24 Apr 2024 15:01:44 +0200
Subject: [PATCH 43/50] update tests

---
 .../ics721-nft-transfer/types/src/class.rs    | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/ibc-apps/ics721-nft-transfer/types/src/class.rs b/ibc-apps/ics721-nft-transfer/types/src/class.rs
index 845e2d36a..ff2ab8cb3 100644
--- a/ibc-apps/ics721-nft-transfer/types/src/class.rs
+++ b/ibc-apps/ics721-nft-transfer/types/src/class.rs
@@ -344,7 +344,7 @@ mod tests {
         assert_eq!(
             PrefixedClassId::from_str("transfer/channel-0/myclass")?,
             PrefixedClassId {
-                trace_path: "transfer/channel-0".parse()?,
+                trace_path: "transfer/channel-0".parse().expect("success"),
                 base_class_id: "myclass".parse()?
             },
             "valid single trace info"
@@ -352,7 +352,9 @@ mod tests {
         assert_eq!(
             PrefixedClassId::from_str("transfer/channel-0/transfer/channel-1/myclass")?,
             PrefixedClassId {
-                trace_path: "transfer/channel-0/transfer/channel-1".parse()?,
+                trace_path: "transfer/channel-0/transfer/channel-1"
+                    .parse()
+                    .expect("success"),
                 base_class_id: "myclass".parse()?
             },
             "valid multiple trace info"
@@ -392,21 +394,24 @@ mod tests {
 
         let prefix_1 = TracePrefix::new("transfer".parse().unwrap(), "channel-1".parse().unwrap());
         let prefix_2 = TracePrefix::new("transfer".parse().unwrap(), "channel-0".parse().unwrap());
-        let mut trace_path = TracePath(vec![prefix_1.clone()]);
+        let mut trace_path = TracePath::from(vec![prefix_1.clone()]);
 
         trace_path.add_prefix(prefix_2.clone());
         assert_eq!(
-            TracePath::from_str("transfer/channel-0/transfer/channel-1")?,
+            TracePath::from_str("transfer/channel-0/transfer/channel-1").expect("success"),
             trace_path
         );
         assert_eq!(
-            TracePath(vec![prefix_1.clone(), prefix_2.clone()]),
+            TracePath::from(vec![prefix_1.clone(), prefix_2.clone()]),
             trace_path
         );
 
         trace_path.remove_prefix(&prefix_2);
-        assert_eq!(TracePath::from_str("transfer/channel-1")?, trace_path);
-        assert_eq!(TracePath(vec![prefix_1.clone()]), trace_path);
+        assert_eq!(
+            TracePath::from_str("transfer/channel-1").expect("success"),
+            trace_path
+        );
+        assert_eq!(TracePath::from(vec![prefix_1.clone()]), trace_path);
 
         trace_path.remove_prefix(&prefix_1);
         assert!(trace_path.is_empty());

From 736d4a1deddd8f5277af4cc731d3fa730e7afd54 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Wed, 24 Apr 2024 15:02:09 +0200
Subject: [PATCH 44/50] accepted class ids

---
 ibc-apps/ics721-nft-transfer/types/src/class.rs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/ibc-apps/ics721-nft-transfer/types/src/class.rs b/ibc-apps/ics721-nft-transfer/types/src/class.rs
index ff2ab8cb3..ffacf32e1 100644
--- a/ibc-apps/ics721-nft-transfer/types/src/class.rs
+++ b/ibc-apps/ics721-nft-transfer/types/src/class.rs
@@ -307,16 +307,16 @@ mod tests {
             "empty base class ID with trace"
         );
         assert!(
-            PrefixedClassId::from_str("/myclass").is_err(),
+            PrefixedClassId::from_str("/myclass").is_ok(),
             "empty prefix"
         );
-        assert!(PrefixedClassId::from_str("//myclass").is_err(), "empty ids");
+        assert!(PrefixedClassId::from_str("//myclass").is_ok(), "empty ids");
         assert!(
-            PrefixedClassId::from_str("transfer/").is_err(),
+            PrefixedClassId::from_str("transfer/").is_ok(),
             "single trace"
         );
         assert!(
-            PrefixedClassId::from_str("transfer/myclass").is_err(),
+            PrefixedClassId::from_str("transfer/myclass").is_ok(),
             "single trace with base class ID"
         );
         assert!(
@@ -328,11 +328,11 @@ mod tests {
             "valid multiple trace info"
         );
         assert!(
-            PrefixedClassId::from_str("(transfer)/channel-0/myclass").is_err(),
+            PrefixedClassId::from_str("(transfer)/channel-0/myclass").is_ok(),
             "invalid port"
         );
         assert!(
-            PrefixedClassId::from_str("transfer/(channel-0)/myclass").is_err(),
+            PrefixedClassId::from_str("transfer/(channel-0)/myclass").is_ok(),
             "invalid channel"
         );
 

From badb01898dd1da1f1346dc88b445dbeee284597d Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Wed, 24 Apr 2024 15:19:25 +0200
Subject: [PATCH 45/50] refactor tests

---
 .../ics721-nft-transfer/types/src/class.rs    | 80 ++++++++++---------
 1 file changed, 41 insertions(+), 39 deletions(-)

diff --git a/ibc-apps/ics721-nft-transfer/types/src/class.rs b/ibc-apps/ics721-nft-transfer/types/src/class.rs
index ffacf32e1..7b820afdd 100644
--- a/ibc-apps/ics721-nft-transfer/types/src/class.rs
+++ b/ibc-apps/ics721-nft-transfer/types/src/class.rs
@@ -295,48 +295,50 @@ impl FromStr for ClassData {
 
 #[cfg(test)]
 mod tests {
+    use rstest::rstest;
+
     use super::*;
 
-    #[test]
-    fn test_class_id_validation() -> Result<(), NftTransferError> {
-        assert!(ClassId::from_str("").is_err(), "empty base class ID");
-        assert!(ClassId::from_str("myclass").is_ok(), "valid base class ID");
-        assert!(PrefixedClassId::from_str("").is_err(), "empty class trace");
-        assert!(
-            PrefixedClassId::from_str("transfer/channel-0/").is_err(),
-            "empty base class ID with trace"
-        );
-        assert!(
-            PrefixedClassId::from_str("/myclass").is_ok(),
-            "empty prefix"
-        );
-        assert!(PrefixedClassId::from_str("//myclass").is_ok(), "empty ids");
-        assert!(
-            PrefixedClassId::from_str("transfer/").is_ok(),
-            "single trace"
-        );
-        assert!(
-            PrefixedClassId::from_str("transfer/myclass").is_ok(),
-            "single trace with base class ID"
-        );
-        assert!(
-            PrefixedClassId::from_str("transfer/channel-0/myclass").is_ok(),
-            "valid single trace info"
-        );
-        assert!(
-            PrefixedClassId::from_str("transfer/channel-0/transfer/channel-1/myclass").is_ok(),
-            "valid multiple trace info"
-        );
-        assert!(
-            PrefixedClassId::from_str("(transfer)/channel-0/myclass").is_ok(),
-            "invalid port"
-        );
-        assert!(
-            PrefixedClassId::from_str("transfer/(channel-0)/myclass").is_ok(),
-            "invalid channel"
-        );
+    #[rstest]
+    #[case("myclass")]
+    #[case("transfer/channel-0/myclass")]
+    #[case("transfer/channel-0/transfer/channel-1/myclass")]
+    #[case("(transfer)/channel-0/myclass")]
+    #[case("transfer/(channel-0)/myclass")]
+    fn test_valid_class_id(#[case] class_id: &str) {
+        ClassId::from_str(class_id).expect("success");
+    }
 
-        Ok(())
+    #[rstest]
+    #[case("")]
+    #[case("")]
+    #[case("  ")]
+    fn test_invalid_class_id(#[case] class_id: &str) {
+        ClassId::from_str(class_id).expect_err("failure");
+    }
+
+    #[rstest]
+    #[case("transfer/channel-0/myclass")]
+    #[case("/myclass")]
+    #[case("//myclass")]
+    #[case("transfer/")]
+    #[case("transfer/myclass")]
+    #[case("transfer/channel-0/myclass")]
+    #[case("transfer/channel-0/transfer/channel-1/myclass")]
+    #[case("(transfer)/channel-0/myclass")]
+    #[case("transfer/(channel-0)/myclass")]
+    #[case("transfer/channel-0///")]
+    fn test_valid_prefixed_class_id(#[case] class_id: &str) {
+        PrefixedClassId::from_str(class_id).expect("success");
+    }
+
+    #[rstest]
+    #[case("")]
+    #[case("  ")]
+    #[case("transfer/channel-0/")]
+    #[case("transfer/channel-0/  ")]
+    fn test_invalid_prefixed_class_id(#[case] class_id: &str) {
+        PrefixedClassId::from_str(class_id).expect_err("failure");
     }
 
     #[test]

From eb9456fabe0582fd0320a607f820d8f128c56768 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Wed, 24 Apr 2024 15:22:27 +0200
Subject: [PATCH 46/50] update changelog entry

---
 .../unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md  | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md b/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md
index c7dd829c3..4bb064600 100644
--- a/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md
+++ b/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md
@@ -1,2 +1,5 @@
-- [ibc-apps-transfer] Bring `PrefixedDenom` parsing up to parity with `ibc-go`.
+- [ibc-app-transfer] Bring `PrefixedDenom` parsing up to parity with `ibc-go`.
   ([\#1177](https://github.com/cosmos/ibc-rs/issues/1177))
+- [ibc-app-nft-transfer] Reuse `TracePrefix` and `TracePath` from
+  `ibc-app-transfer-types`.
+  ([\#1178](https://github.com/cosmos/ibc-rs/pull/1178))

From 43e46ad7c1e74cde789d62641bdf3a678b3fe1d3 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Thu, 25 Apr 2024 12:15:36 +0200
Subject: [PATCH 47/50] opt trace prefix and path parsing

---
 ibc-apps/ics20-transfer/types/src/denom.rs    | 65 ++++++++++++-------
 .../ics721-nft-transfer/types/src/class.rs    | 18 ++---
 2 files changed, 53 insertions(+), 30 deletions(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index b6a85dd2d..624ad0275 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -86,17 +86,24 @@ impl TracePrefix {
 
     /// Returns a string slice with [`TracePrefix`] removed.
     ///
-    /// If the string starts with a [`TracePrefix`], i.e. `{port-id}/channel-{id}/`,
+    /// If the string starts with a [`TracePrefix`], i.e. `{port-id}/channel-{id}`,
     /// it returns a tuple of the removed [`TracePrefix`] and the substring after the prefix.
     ///
+    /// If the substring is empty, it returns `None`.
+    /// Otherwise the substring starts with `/`. In that case,
+    /// the leading `/` is stripped and returned.
+    ///
     /// If the string does not start with a [`TracePrefix`], this method returns `None`.
     ///
     /// This method is analogous to `strip_prefix` from the standard library.
-    pub fn strip(s: &str) -> Option<(Self, &str)> {
+    pub fn strip(s: &str) -> Option<(Self, Option<&str>)> {
         // The below two chained `split_once` calls emulate a virtual `split_twice` call,
         // which is not available in the standard library.
         let (port_id_s, remaining) = s.split_once('/')?;
-        let (channel_id_s, remaining) = remaining.split_once('/')?;
+        let (channel_id_s, remaining) = remaining
+            .split_once('/')
+            .map(|(a, b)| (a, Some(b)))
+            .unwrap_or_else(|| (remaining, None));
 
         let port_id = port_id_s.parse().ok()?;
         let channel_id = channel_id_s.parse().ok()?;
@@ -166,22 +173,37 @@ impl TracePath {
     /// If the string starts with a [`TracePath`], it returns a tuple of the removed
     /// [`TracePath`] and the substring after the [`TracePath`].
     ///
+    /// If the substring is empty, it returns `None`.
+    /// Otherwise the substring starts with `/`. In that case,
+    /// the leading `/` is stripped and returned.
+    ///
     /// If the string does not contain any [`TracePrefix`], it returns the original string.
     ///
     /// This method is analogous to `trim_start_matches` from the standard library.
-    pub fn trim(s: &str) -> (Self, &str) {
+    pub fn trim(s: &str) -> (Self, Option<&str>) {
+        // We can't use `TracePrefix::empty()` with `TracePrefix::add_prefix()`.
+        // Because we are stripping prefixes in reverse order.
         let mut trace_prefixes = vec![];
-        let mut remaining_parts = s;
+        let mut current_remaining_opt = Some(s);
+
+        loop {
+            let Some(current_remaining_s) = current_remaining_opt else {
+                break;
+            };
+
+            let Some((trace_prefix, next_remaining_opt)) = TracePrefix::strip(current_remaining_s)
+            else {
+                break;
+            };
 
-        while let Some((trace_prefix, remaining)) = TracePrefix::strip(remaining_parts) {
             trace_prefixes.push(trace_prefix);
-            remaining_parts = remaining;
+            current_remaining_opt = next_remaining_opt;
         }
 
-        // reversing is needed, as [`TracePath`] requires quick addition/removal
+        // Reversing is needed, as [`TracePath`] requires quick addition/removal
         // of prefixes which is more performant from the end of a [`Vec`].
         trace_prefixes.reverse();
-        (Self(trace_prefixes), remaining_parts)
+        (Self(trace_prefixes), current_remaining_opt)
     }
 }
 
@@ -193,12 +215,9 @@ impl FromStr for TracePath {
             return Ok(TracePath::empty());
         }
 
-        // This is needed as TracePath trims `{port-id}/{channel-id}/`.
-        let slashed_s = format!("{}/", s);
-
-        let (trace_path, remaining_parts) = TracePath::trim(slashed_s.as_str());
+        let (trace_path, remaining_parts) = TracePath::trim(s);
         remaining_parts
-            .is_empty()
+            .is_none()
             .then_some(trace_path)
             .ok_or_else(|| TokenTransferError::MalformedTrace(s.to_string()))
     }
@@ -328,14 +347,16 @@ impl FromStr for PrefixedDenom {
     /// The loop breaks at this point, resulting in a [`TracePath`] of `"transfer/channel-75"`
     /// and a [`BaseDenom`] of `"factory/stars16da2uus9zrsy83h23ur42v3lglg5rmyrpqnju4/dust"`.
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let (trace_path, remaining_parts) = TracePath::trim(s);
-
-        let base_denom = BaseDenom::from_str(remaining_parts)?;
-
-        Ok(Self {
-            trace_path,
-            base_denom,
-        })
+        match TracePath::trim(s) {
+            (trace_path, Some(remaining_parts)) => Ok(Self {
+                trace_path,
+                base_denom: BaseDenom::from_str(remaining_parts)?,
+            }),
+            (_, None) => Ok(Self {
+                trace_path: TracePath::empty(),
+                base_denom: BaseDenom::from_str(s)?,
+            }),
+        }
     }
 }
 
diff --git a/ibc-apps/ics721-nft-transfer/types/src/class.rs b/ibc-apps/ics721-nft-transfer/types/src/class.rs
index 7b820afdd..ff1293f89 100644
--- a/ibc-apps/ics721-nft-transfer/types/src/class.rs
+++ b/ibc-apps/ics721-nft-transfer/types/src/class.rs
@@ -124,14 +124,16 @@ impl FromStr for PrefixedClassId {
     /// The parsing logic is same as [`FromStr`] impl of
     /// [`PrefixedDenom`](ibc_app_transfer_types::PrefixedDenom) from ICS-20.
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let (trace_path, remaining_parts) = TracePath::trim(s);
-
-        let base_class_id = ClassId::from_str(remaining_parts)?;
-
-        Ok(Self {
-            trace_path,
-            base_class_id,
-        })
+        match TracePath::trim(s) {
+            (trace_path, Some(remaining_parts)) => Ok(Self {
+                trace_path,
+                base_class_id: ClassId::from_str(remaining_parts)?,
+            }),
+            (_, None) => Ok(Self {
+                trace_path: TracePath::empty(),
+                base_class_id: ClassId::from_str(s)?,
+            }),
+        }
     }
 }
 

From a7846403dd1677cafd72da8e2d8cc74c7e1304e8 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Thu, 25 Apr 2024 12:15:44 +0200
Subject: [PATCH 48/50] add new tests

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 624ad0275..5cae4701d 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -597,6 +597,25 @@ mod tests {
         assert_eq!(prefixed_denom.to_string(), "uatom");
     }
 
+    #[rstest]
+    #[case("", TracePath::empty(), Some(""))]
+    #[case("transfer", TracePath::empty(), Some("transfer"))]
+    #[case("transfer/", TracePath::empty(), Some("transfer/"))]
+    #[case("transfer/channel-1", TracePath::from(vec![TracePrefix::new("transfer".parse().unwrap(), ChannelId::new(1))]), None)]
+    #[case("transfer/channel-1/", TracePath::from(vec![TracePrefix::new("transfer".parse().unwrap(), ChannelId::new(1))]), Some(""))]
+    #[case("transfer/channel-1/uatom", TracePath::from(vec![TracePrefix::new("transfer".parse().unwrap(), ChannelId::new(1))]), Some("uatom"))]
+    #[case("transfer/channel-1/uatom/", TracePath::from(vec![TracePrefix::new("transfer".parse().unwrap(), ChannelId::new(1))]), Some("uatom/"))]
+    fn test_trace_path_cases(
+        #[case] trace_path_s: &str,
+        #[case] trace_path: TracePath,
+        #[case] remaining: Option<&str>,
+    ) {
+        let (parsed_trace_path, parsed_remaining) = TracePath::trim(trace_path_s);
+
+        assert_eq!(parsed_trace_path, trace_path);
+        assert_eq!(parsed_remaining, remaining);
+    }
+
     #[test]
     fn test_trace_path() -> Result<(), TokenTransferError> {
         assert!(TracePath::from_str("").is_ok(), "empty trace path");

From 7f465b0af5749d1711205fd86b8c6a219976f4c8 Mon Sep 17 00:00:00 2001
From: Sean Chen <seanchen11235@gmail.com>
Date: Fri, 26 Apr 2024 10:03:51 -0500
Subject: [PATCH 49/50] Update changelog entry

---
 .../unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md     | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md b/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md
index 4bb064600..cf89e9a52 100644
--- a/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md
+++ b/.changelog/unreleased/bug-fixes/1177-fix-prefixed-denom-parsing.md
@@ -1,5 +1,5 @@
 - [ibc-app-transfer] Bring `PrefixedDenom` parsing up to parity with `ibc-go`.
   ([\#1177](https://github.com/cosmos/ibc-rs/issues/1177))
 - [ibc-app-nft-transfer] Reuse `TracePrefix` and `TracePath` from
-  `ibc-app-transfer-types`.
+  `ibc-app-transfer-types` when parsing `PrefixedClassId`.
   ([\#1178](https://github.com/cosmos/ibc-rs/pull/1178))

From 53fad12fe60e4248e74a476578cf1999e3d3ba34 Mon Sep 17 00:00:00 2001
From: Ranadeep Biswas <mail@rnbguy.at>
Date: Fri, 26 Apr 2024 17:43:33 +0200
Subject: [PATCH 50/50] fix trace-prefix index order

---
 ibc-apps/ics20-transfer/types/src/denom.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ibc-apps/ics20-transfer/types/src/denom.rs b/ibc-apps/ics20-transfer/types/src/denom.rs
index 5cae4701d..8ac632fea 100644
--- a/ibc-apps/ics20-transfer/types/src/denom.rs
+++ b/ibc-apps/ics20-transfer/types/src/denom.rs
@@ -326,7 +326,7 @@ impl FromStr for PrefixedDenom {
     type Err = TokenTransferError;
 
     /// Initializes a [`PrefixedDenom`] from a string that adheres to the format
-    /// `{1st-port-id/channel-<index>}/{2nd-port-id/channel-<index>}/.../{nth-port-id/channel-<index>}/<base_denom>`.
+    /// `{nth-port-id/channel-<index>}/{(n-1)th-port-id/channel-<index>}/.../{1st-port-id/channel-<index>}/<base_denom>`.
     /// A [`PrefixedDenom`] exhibits a sequence of `{ith-port-id/channel-<index>}` pairs.
     /// This sequence makes up the [`TracePath`] of the [`PrefixedDenom`].
     ///