From 441d95c40ee1393134c669a4f98d35e24d42afea Mon Sep 17 00:00:00 2001
From: ffranr <robyn@lightning.engineering>
Date: Thu, 19 Jan 2023 14:04:23 +0000
Subject: [PATCH] clientdb: add snapshot of spending accounts to local batch
 snapshot

The account versions from the spending accounts snapshot will be used in estimating on-chain fees.
---
 clientdb/batch.go          |  7 +++++--
 clientdb/batch_snapshot.go | 36 +++++++++++++++++++++++++++---------
 2 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/clientdb/batch.go b/clientdb/batch.go
index a76fd94d4..d3aa8c9ba 100644
--- a/clientdb/batch.go
+++ b/clientdb/batch.go
@@ -105,6 +105,8 @@ func (db *DB) StorePendingBatch(batch *order.Batch, orders []order.Nonce,
 			return err
 		}
 
+		spendingAccountsSnapshot := accounts
+
 		var updatedAccounts []*account.Account
 		for idx, acct := range accounts {
 			accountKey := getAccountKey(acct)
@@ -125,10 +127,11 @@ func (db *DB) StorePendingBatch(batch *order.Batch, orders []order.Nonce,
 			return err
 		}
 
-		// Before we are done, we store a snapshot of the this batch,
+		// Before we are done, we store a snapshot of the batch,
 		// so we retain this history for later.
 		snapshot, err := NewSnapshot(
-			batch, updatedOrders, updatedAccounts,
+			batch, updatedOrders, spendingAccountsSnapshot,
+			updatedAccounts,
 		)
 		if err != nil {
 			return err
diff --git a/clientdb/batch_snapshot.go b/clientdb/batch_snapshot.go
index d9bd9b0d7..3daf6ae95 100644
--- a/clientdb/batch_snapshot.go
+++ b/clientdb/batch_snapshot.go
@@ -82,6 +82,14 @@ type LocalBatchSnapshot struct {
 	// the batch transaction.
 	BatchTxFeeRate chainfee.SatPerKWeight
 
+	// spendingAccountsSnapshot is a snapshot of the local accounts that
+	// participated in this batch before any potential account updates were
+	// applied.
+	//
+	// NOTE: this field is used for estimating on-chains fee using the
+	// account version.
+	SpendingAccountsSnapshot map[[33]byte]*account.Account
+
 	// Account holds snapshots of the ending state of the local accounts
 	// that participated in this batch.
 	Accounts map[[33]byte]*account.Account
@@ -97,6 +105,7 @@ type LocalBatchSnapshot struct {
 
 // NewSnapshot creates a new LocalBatchSnapshot from the passed order batched.
 func NewSnapshot(batch *order.Batch, ourOrders []order.Order,
+	spendingAccountsSnapshot []*account.Account,
 	accounts []*account.Account) (*LocalBatchSnapshot, error) {
 
 	// We only support LinearFeeSchedule at this point (because of
@@ -107,6 +116,14 @@ func NewSnapshot(batch *order.Batch, ourOrders []order.Order,
 			batch.ExecutionFee)
 	}
 
+	// Reformulate account data structure into a map keyed on trader key.
+	spendingAccsSnapshot := make(map[[33]byte]*account.Account)
+	for _, a := range accounts {
+		var key [33]byte
+		copy(key[:], a.TraderKey.PubKey.SerializeCompressed())
+		spendingAccsSnapshot[key] = a
+	}
+
 	as := make(map[[33]byte]*account.Account)
 	for _, a := range accounts {
 		var key [33]byte
@@ -120,15 +137,16 @@ func NewSnapshot(batch *order.Batch, ourOrders []order.Order,
 	}
 
 	snapshot := &LocalBatchSnapshot{
-		Version:        batch.Version,
-		BatchID:        batch.ID,
-		ClearingPrices: batch.ClearingPrices,
-		ExecutionFee:   *feeSched,
-		BatchTX:        batch.BatchTX,
-		BatchTxFeeRate: batch.BatchTxFeeRate,
-		Accounts:       as,
-		Orders:         os,
-		MatchedOrders:  batch.MatchedOrders,
+		Version:                  batch.Version,
+		BatchID:                  batch.ID,
+		ClearingPrices:           batch.ClearingPrices,
+		ExecutionFee:             *feeSched,
+		BatchTX:                  batch.BatchTX,
+		BatchTxFeeRate:           batch.BatchTxFeeRate,
+		SpendingAccountsSnapshot: spendingAccsSnapshot,
+		Accounts:                 as,
+		Orders:                   os,
+		MatchedOrders:            batch.MatchedOrders,
 	}
 
 	return snapshot, nil