implement fs shims

shims/fs/sync.js

@@ -0,0 +1,81 @@
+// Synchronous fs method implementations
+// Served from caches where possible, sync XHR fallback for uncached content.
+
+export function createFsSync(metadataCache, contentCache, transport) {
+  return {
+    existsSync(path) {
+      return metadataCache.has(path);
+    },
+
+    statSync(path) {
+      const stat = metadataCache.toStat(path);
+      if (!stat) {
+        const err = new Error(`ENOENT: no such file or directory, stat '${path}'`);
+        err.code = 'ENOENT';
+        throw err;
+      }
+      return stat;
+    },
+
+    accessSync(path, mode) {
+      if (!metadataCache.has(path)) {
+        const err = new Error(`ENOENT: no such file or directory, access '${path}'`);
+        err.code = 'ENOENT';
+        throw err;
+      }
+    },
+
+    readFileSync(path, encoding) {
+      if (typeof encoding === 'object') encoding = encoding?.encoding;
+
+      // Try content cache first
+      const cached = contentCache.get(path);
+      if (cached !== null) {
+        if (encoding === 'utf8' || encoding === 'utf-8') {
+          return typeof cached === 'string' ? cached : new TextDecoder().decode(cached);
+        }
+        return cached;
+      }
+
+      // Fallback: synchronous XHR
+      console.warn('[shim:fs] readFileSync cache miss, using sync XHR:', path);
+      const data = transport.readFileSync(path, encoding);
+      contentCache.set(path, data);
+      return data;
+    },
+
+    writeFileSync(path, data, encoding) {
+      if (typeof encoding === 'object') encoding = encoding?.encoding;
+
+      // Write to cache immediately (sync return)
+      contentCache.set(path, data);
+      const size = typeof data === 'string' ? data.length : (data.byteLength || 0);
+      metadataCache.set(path, {
+        type: 'file',
+        size,
+        mtime: Date.now(),
+        ctime: metadataCache.get(path)?.ctime || Date.now(),
+      });
+
+      // Fire-and-forget async send to server
+      transport.writeFile(path, data, encoding).catch((e) => {
+        console.error('[shim:fs] writeFileSync background save failed:', path, e);
+      });
+    },
+
+    unlinkSync(path) {
+      contentCache.delete(path);
+      metadataCache.delete(path);
+
+      // Fire-and-forget
+      transport.unlink(path).catch((e) => {
+        console.error('[shim:fs] unlinkSync background delete failed:', path, e);
+      });
+    },
+
+    readdirSync(path) {
+      const entries = metadataCache.readdir(path);
+      return entries.map(e => e.name);
+    },
+  };
+}