Define grep_file_contents interface.

crates/rrg/src/action/grep_file_contents.rs

@@ -3,12 +3,22 @@
 // Use of this source code is governed by an MIT-style license that can be found
 // in the LICENSE file or at https://opensource.org/licenses/MIT.
 
+use std::path::PathBuf;
+
 /// Arguments of the `grep_file_contents` action.
 pub struct Args {
+    /// Path to the file to grep the contents of.
+    path: PathBuf,
+    /// Regular expression to search for in the file contents.
+    regex: regex::Regex,
 }
 
 /// Result of the `grep_file_contents` action.
 pub struct Item {
+    /// Byte offset within the file from which the content matched.
+    offset: u64,
+    /// Content that matched the specified regular expression.
+    content: String,
 }
 
 /// Handles invocations of the `grep_file_contents` action.
@@ -23,8 +33,19 @@ impl crate::request::Args for Args {
 
     type Proto = rrg_proto::grep_file_contents::Args;
 
-    fn from_proto(proto: Self::Proto) -> Result<Args, crate::request::ParseArgsError> {
-        todo!()
+    fn from_proto(mut proto: Self::Proto) -> Result<Args, crate::request::ParseArgsError> {
+        use crate::request::ParseArgsError;
+
+        let path = PathBuf::try_from(proto.take_path())
+            .map_err(|error| ParseArgsError::invalid_field("path", error))?;
+
+        let regex = regex::Regex::new(proto.regex())
+            .map_err(|error| ParseArgsError::invalid_field("regex", error))?;
+
+        Ok(Args {
+            path,
+            regex,
+        })
     }
 }
 
@@ -33,6 +54,10 @@ impl crate::response::Item for Item {
     type Proto = rrg_proto::grep_file_contents::Result;
 
     fn into_proto(self) -> Self::Proto {
-        todo!()
+        let mut proto = Self::Proto::default();
+        proto.set_offset(self.offset);
+        proto.set_content(self.content);
+
+        proto
     }
 }

proto/rrg/action/grep_file_contents.proto

@@ -9,7 +9,30 @@ package rrg.action.get_file_contents;
 import "rrg/fs.proto";
 
 message Args {
+    // Absolute path to the file to grep the contents of.
+    //
+    // The file content must be valid UTF-8.
+    rrg.fs.Path path = 1;
+
+    // Regular expression to search for in the file contents.
+    //
+    // The specific syntax of the regex language is left unspecified as the
+    // implementation detail but most common regex features can be expected to
+    // be supported.
+    string regex = 2;
+
+    // TODO(@panhania): Add support for files that not necessarily conform to
+    // Unicode.
+
+    // TODO(@panhania): Add support for different file encodings.
 }
 
 message Result {
+    // Byte offset within the file from which the content matched.
+    uint64 offset = 1;
+
+    // Content that matched the specified regular expression.
+    string content = 2;
+
+    // TODO(@panhania): Add support for capture groups.
 }