perf(renderer): cache activity render signatures

src/renderer/components/team/activity/activityRenderCache.ts

@@ -6,6 +6,10 @@ const MAX_ACTIVITY_RENDER_CACHE_ENTRIES = 500;
 
 type StringCache = Map<string, string>;
 
+const taskRefsSignatureCache = new WeakMap<readonly TaskRef[], string>();
+const stringArraySignatureCache = new WeakMap<readonly string[], string>();
+const stringMapSignatureCache = new WeakMap<ReadonlyMap<string, string>, string>();
+
 export function getCachedString(cache: StringCache, key: string, buildValue: () => string): string {
   const cached = cache.get(key);
   if (cached !== undefined || cache.has(key)) return cached ?? '';
@@ -20,42 +24,60 @@ export function getCachedString(cache: StringCache, key: string, buildValue: ()
 }
 
 export function encodeCacheParts(parts: readonly string[]): string {
-  const encodedParts: string[] = [];
-  for (const part of parts) {
-    pushEncodedCachePart(encodedParts, part);
+  let encoded = '';
+  for (let index = 0; index < parts.length; index += 1) {
+    if (index > 0) encoded += '|';
+    const part = parts[index];
+    encoded += `${part.length}:${part}`;
   }
-  return encodedParts.join('|');
+  return encoded;
 }
 
 export function taskRefsCacheSignature(taskRefs?: readonly TaskRef[]): string {
   if (!taskRefs || taskRefs.length === 0) return '';
-  const encodedParts: string[] = [];
-  for (const ref of taskRefs) {
-    pushEncodedCachePart(encodedParts, ref.taskId);
-    pushEncodedCachePart(encodedParts, ref.displayId);
-    pushEncodedCachePart(encodedParts, ref.teamName ?? '');
+  const cached = taskRefsSignatureCache.get(taskRefs);
+  if (cached !== undefined) return cached;
+
+  let encoded = '';
+  let hasPart = false;
+  for (let index = 0; index < taskRefs.length; index += 1) {
+    const ref = taskRefs[index];
+    const parts = [ref.taskId, ref.displayId, ref.teamName ?? ''];
+    for (const part of parts) {
+      if (hasPart) encoded += '|';
+      encoded += `${part.length}:${part}`;
+      hasPart = true;
+    }
   }
-  return encodedParts.join('|');
+  taskRefsSignatureCache.set(taskRefs, encoded);
+  return encoded;
 }
 
 export function stringArrayCacheSignature(values?: readonly string[]): string {
   if (!values || values.length === 0) return '';
-  return encodeCacheParts(values);
+  const cached = stringArraySignatureCache.get(values);
+  if (cached !== undefined) return cached;
+  const signature = encodeCacheParts(values);
+  stringArraySignatureCache.set(values, signature);
+  return signature;
 }
 
 export function stringMapCacheSignature(map?: ReadonlyMap<string, string>): string {
   if (!map || map.size === 0) return '';
-  const entries = [...map.entries()].sort(([a], [b]) => a.localeCompare(b));
-  const encodedParts: string[] = [];
-  for (const [key, value] of entries) {
-    pushEncodedCachePart(encodedParts, key);
-    pushEncodedCachePart(encodedParts, value);
-  }
-  return encodedParts.join('|');
-}
+  const cached = stringMapSignatureCache.get(map);
+  if (cached !== undefined) return cached;
 
-function pushEncodedCachePart(encodedParts: string[], part: string): void {
-  encodedParts.push(`${part.length}:${part}`);
+  const entries = [...map.entries()].sort(([a], [b]) => a.localeCompare(b));
+  let encoded = '';
+  let hasPart = false;
+  for (const [key, value] of entries) {
+    if (hasPart) encoded += '|';
+    encoded += `${key.length}:${key}`;
+    hasPart = true;
+    encoded += `|${value.length}:${value}`;
+  }
+  stringMapSignatureCache.set(map, encoded);
+  return encoded;
 }
 
 const markdownPlainTextCache: StringCache = new Map();

test/renderer/components/team/activity/activityRenderCache.test.ts

@@ -0,0 +1,43 @@
+import { describe, expect, it } from 'vitest';
+
+import {
+  encodeCacheParts,
+  stringArrayCacheSignature,
+  stringMapCacheSignature,
+  taskRefsCacheSignature,
+} from '../../../../../src/renderer/components/team/activity/activityRenderCache';
+
+import type { TaskRef } from '../../../../../src/shared/types';
+
+describe('activityRenderCache', () => {
+  it('encodes cache parts with length prefixes', () => {
+    expect(encodeCacheParts(['a', 'bb', ''])).toBe('1:a|2:bb|0:');
+  });
+
+  it('builds stable task reference signatures', () => {
+    const refs: TaskRef[] = [
+      { taskId: 'task-1', displayId: '#1', teamName: 'team-a' },
+      { taskId: 'task-2', displayId: '#2' },
+    ];
+
+    expect(taskRefsCacheSignature(refs)).toBe('6:task-1|2:#1|6:team-a|6:task-2|2:#2|0:');
+    expect(taskRefsCacheSignature(refs)).toBe(taskRefsCacheSignature(refs));
+  });
+
+  it('builds stable string array signatures', () => {
+    const values = ['alice', 'bob'];
+
+    expect(stringArrayCacheSignature(values)).toBe('5:alice|3:bob');
+    expect(stringArrayCacheSignature(values)).toBe(stringArrayCacheSignature(values));
+  });
+
+  it('sorts string map signatures by key', () => {
+    const map = new Map([
+      ['bob', 'blue'],
+      ['alice', 'red'],
+    ]);
+
+    expect(stringMapCacheSignature(map)).toBe('5:alice|3:red|3:bob|4:blue');
+    expect(stringMapCacheSignature(map)).toBe(stringMapCacheSignature(map));
+  });
+});