From b07d141f4ce40f939d18661d4860911a50e7e3d6 Mon Sep 17 00:00:00 2001
From: Lewis <lewis@tangled.org>
Date: Mon, 29 Jun 2026 20:28:29 +0300
Subject: [PATCH] appview/pulls: cache combined diffs in 15m lru

Lewis: May this revision serve well! <lewis@tangled.org>
---
 appview/pulls/pulls.go  | 10 ++++++++++
 appview/pulls/single.go | 17 ++++++++++++++---
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/appview/pulls/pulls.go b/appview/pulls/pulls.go
index 99764cdb..beb3cadb 100644
--- a/appview/pulls/pulls.go
+++ b/appview/pulls/pulls.go
@@ -7,6 +7,7 @@ import (
 	"io"
 	"log/slog"
 	"strings"
+	"time"
 
 	"tangled.org/core/appview/config"
 	"tangled.org/core/appview/db"
@@ -21,12 +22,19 @@ import (
 	"tangled.org/core/idresolver"
 	"tangled.org/core/ogre"
 	"tangled.org/core/patchutil"
+	"tangled.org/core/types"
 
+	"github.com/hashicorp/golang-lru/v2/expirable"
 	indigoxrpc "github.com/bluesky-social/indigo/xrpc"
 )
 
 const ApplicationGzip = "application/gzip"
 
+const (
+	diffCacheSize = 128
+	diffCacheTTL  = 15 * time.Minute
+)
+
 type Pulls struct {
 	oauth            *oauth.OAuth
 	repoResolver     *reporesolver.RepoResolver
@@ -40,6 +48,7 @@ type Pulls struct {
 	logger           *slog.Logger
 	indexer          *pulls_indexer.Indexer
 	ogreClient       *ogre.Client
+	diffCache        *expirable.LRU[string, types.DiffRenderer]
 }
 
 func New(
@@ -68,6 +77,7 @@ func New(
 		logger:           logger,
 		indexer:          indexer,
 		ogreClient:       ogre.NewClient(config.Ogre.Host),
+		diffCache:        expirable.NewLRU[string, types.DiffRenderer](diffCacheSize, nil, diffCacheTTL),
 	}
 }
 
diff --git a/appview/pulls/single.go b/appview/pulls/single.go
index c166f637..5280ed0f 100644
--- a/appview/pulls/single.go
+++ b/appview/pulls/single.go
@@ -226,10 +226,7 @@ func (s *Pulls) repoPullHelper(w http.ResponseWriter, r *http.Request, interdiff
 		vouchSkips[ownerDid] = skipped
 	}
 
-	patch := pull.Submissions[roundIdInt].CombinedPatch()
 	var diff types.DiffRenderer
-	diff = patchutil.AsNiceDiff(patch, pull.TargetBranch)
-
 	if interdiff {
 		currentPatch, err := patchutil.AsDiff(pull.Submissions[roundIdInt].CombinedPatch())
 		if err != nil {
@@ -246,6 +243,8 @@ func (s *Pulls) repoPullHelper(w http.ResponseWriter, r *http.Request, interdiff
 		}
 
 		diff = patchutil.Interdiff(previousPatch, currentPatch)
+	} else {
+		diff = s.combinedDiff(pull, roundIdInt)
 	}
 
 	err = s.pages.RepoSinglePull(w, pages.RepoSinglePullParams{
@@ -275,6 +274,18 @@ func (s *Pulls) repoPullHelper(w http.ResponseWriter, r *http.Request, interdiff
 	}
 }
 
+func (s *Pulls) combinedDiff(pull *models.Pull, round int) types.DiffRenderer {
+	submission := pull.Submissions[round]
+	key := fmt.Sprintf("%s|%d|%s", pull.AtUri(), round, submission.SourceRev)
+	if cached, ok := s.diffCache.Get(key); ok {
+		return cached
+	}
+
+	diff := patchutil.AsNiceDiff(submission.CombinedPatch(), pull.TargetBranch)
+	s.diffCache.Add(key, diff)
+	return diff
+}
+
 func (s *Pulls) RepoSinglePull(w http.ResponseWriter, r *http.Request) {
 	l := s.logger.With("handler", "RepoSinglePull")
 
-- 
2.51.2