Initial open source release

lib/wx-image.ts

@@ -0,0 +1,148 @@
+import { existsSync, readdirSync, readFileSync, statSync } from 'node:fs';
+import { homedir } from 'node:os';
+import { join } from 'node:path';
+import * as fsp from 'node:fs/promises';
+
+// Node 22+ ships fs.promises.glob but TS types lag behind
+const glob = (fsp as unknown as {
+  glob: (pattern: string, opts: { cwd: string }) => AsyncIterable<string>;
+}).glob;
+
+const WX_CACHE_ROOT = join(
+  /*turbopackIgnore: true*/ homedir(),
+  'Library/Containers/com.tencent.xinWeChat/Data/Documents/xwechat_files',
+);
+
+let _userDirCache: string | null = null;
+
+/** 找到当前微信用户目录（取最近修改的） */
+function findUserDir(): string | null {
+  if (_userDirCache && existsSync(/*turbopackIgnore: true*/ _userDirCache)) return _userDirCache;
+  if (!existsSync(/*turbopackIgnore: true*/ WX_CACHE_ROOT)) return null;
+  const entries = readdirSync(/*turbopackIgnore: true*/ WX_CACHE_ROOT, { withFileTypes: true })
+    .filter((e) => e.isDirectory() && e.name !== 'all_users' && e.name !== 'Backup')
+    .map((e) => {
+      const p = join(/*turbopackIgnore: true*/ WX_CACHE_ROOT, e.name);
+      return { p, mtime: statSync(/*turbopackIgnore: true*/ p).mtimeMs };
+    })
+    .sort((a, b) => b.mtime - a.mtime);
+  if (entries.length === 0) return null;
+  _userDirCache = entries[0].p;
+  return _userDirCache;
+}
+
+/** 列出按月分的子目录，按时间倒序（最近月份优先） */
+function listMonthDirs(userDir: string): string[] {
+  const cacheDir = join(/*turbopackIgnore: true*/ userDir, 'cache');
+  if (!existsSync(/*turbopackIgnore: true*/ cacheDir)) return [];
+  return readdirSync(/*turbopackIgnore: true*/ cacheDir)
+    .filter((d) => /^\d{4}-\d{2}$/.test(d))
+    .sort((a, b) => b.localeCompare(a));
+}
+
+export interface ResolvedImage {
+  path: string;
+  type: 'hd' | 'mid' | 'thumb';
+  format: 'png' | 'jpeg' | 'gif' | 'bmp' | 'bin';
+}
+
+/** 检测文件 magic bytes */
+function detectFormat(path: string): ResolvedImage['format'] {
+  try {
+    const fd = readFileSync(/*turbopackIgnore: true*/ path, { flag: 'r' });
+    const h = fd.subarray(0, 4);
+    if (h[0] === 0xff && h[1] === 0xd8) return 'jpeg';
+    if (h[0] === 0x89 && h[1] === 0x50 && h[2] === 0x4e && h[3] === 0x47) return 'png';
+    if (h[0] === 0x47 && h[1] === 0x49 && h[2] === 0x46) return 'gif';
+    if (h[0] === 0x42 && h[1] === 0x4d) return 'bmp';
+  } catch {}
+  return 'bin';
+}
+
+// 月份 → { localId → ResolvedImage } 索引（懒加载）
+const monthIndexCache = new Map<string, Map<number, ResolvedImage>>();
+const monthIndexLoading = new Map<string, Promise<void>>();
+
+async function buildMonthIndex(userDir: string, month: string): Promise<void> {
+  if (monthIndexCache.has(month)) return;
+  const existing = monthIndexLoading.get(month);
+  if (existing) return existing;
+
+  const p = (async () => {
+    const monthRoot = join(/*turbopackIgnore: true*/ userDir, 'cache', month, 'Message');
+    if (!existsSync(/*turbopackIgnore: true*/ monthRoot)) {
+      monthIndexCache.set(month, new Map());
+      return;
+    }
+    const idx = new Map<number, ResolvedImage>();
+    const priority: Record<ResolvedImage['type'], number> = { hd: 3, mid: 2, thumb: 1 };
+
+    const consider = (path: string, type: ResolvedImage['type']) => {
+      const m = /\/(\d+)_/.exec(path);
+      if (!m) return;
+      const id = Number(m[1]);
+      const cur = idx.get(id);
+      if (!cur || priority[type] > priority[cur.type]) {
+        // 推迟 detectFormat 到实际请求时
+        idx.set(id, { path, type, format: 'bin' });
+      }
+    };
+
+    for await (const p of glob('*/ImageTemp/*hd_temp_convert', { cwd: monthRoot })) {
+      consider(join(/*turbopackIgnore: true*/ monthRoot, String(p)), 'hd');
+    }
+    for await (const p of glob('*/ImageTemp/*mid_temp_convert', { cwd: monthRoot })) {
+      consider(join(/*turbopackIgnore: true*/ monthRoot, String(p)), 'mid');
+    }
+    for await (const p of glob('*/Thumb/*thumb.jpg', { cwd: monthRoot })) {
+      consider(join(/*turbopackIgnore: true*/ monthRoot, String(p)), 'thumb');
+    }
+    monthIndexCache.set(month, idx);
+  })();
+
+  monthIndexLoading.set(month, p);
+  await p;
+  monthIndexLoading.delete(month);
+}
+
+/**
+ * 按 local_id 在 wx 缓存找图。优先 hint 月份，否则按月扫到旧。
+ * 用懒加载的内存索引加速：每月扫一次后命中 ~1ms。
+ */
+export async function resolveWxImage(
+  localId: number,
+  hintMonth?: string,
+): Promise<ResolvedImage | null> {
+  const userDir = findUserDir();
+  if (!userDir) return null;
+
+  const months = listMonthDirs(userDir);
+  if (months.length === 0) return null;
+
+  const ordered = hintMonth && months.includes(hintMonth)
+    ? [hintMonth, ...months.filter((m) => m !== hintMonth)]
+    : months;
+
+  for (const m of ordered) {
+    await buildMonthIndex(userDir, m);
+    const idx = monthIndexCache.get(m);
+    if (!idx) continue;
+    const hit = idx.get(localId);
+    if (hit) {
+      return { ...hit, format: detectFormat(hit.path) };
+    }
+  }
+  return null;
+}
+
+const MIME: Record<ResolvedImage['format'], string> = {
+  png: 'image/png',
+  jpeg: 'image/jpeg',
+  gif: 'image/gif',
+  bmp: 'image/bmp',
+  bin: 'application/octet-stream',
+};
+
+export function mimeFor(format: ResolvedImage['format']): string {
+  return MIME[format];
+}