implement fs shims

shims/fs/index.js

@@ -0,0 +1,52 @@
+// Filesystem shim  -  the core piece
+// Returned for both require('original-fs') and require('fs')
+//
+// Strategy: metadata cache + on-demand content fetch + write-through
+// Server sync mechanism (REST vs WebSocket) is TBD  -  abstracted behind
+// the transport layer in ./transport.js
+
+import { MetadataCache } from './metadata-cache.js';
+import { ContentCache } from './content-cache.js';
+import { transport } from './transport.js';
+import { createFsPromises } from './promises.js';
+import { createFsSync } from './sync.js';
+import { createFsWatch } from './watch.js';
+import { constants } from './constants.js';
+
+const metadataCache = new MetadataCache();
+const contentCache = new ContentCache();
+
+const fsPromises = createFsPromises(metadataCache, contentCache, transport);
+const fsSync = createFsSync(metadataCache, contentCache, transport);
+const fsWatch = createFsWatch(transport);
+
+export const fsShim = {
+  // Async promise-based API (this.fsPromises = this.fs.promises)
+  promises: fsPromises,
+
+  // Sync methods
+  existsSync: fsSync.existsSync,
+  readFileSync: fsSync.readFileSync,
+  writeFileSync: fsSync.writeFileSync,
+  unlinkSync: fsSync.unlinkSync,
+  accessSync: fsSync.accessSync,
+  statSync: fsSync.statSync,
+  readdirSync: fsSync.readdirSync,
+
+  // Watch
+  watch: fsWatch.watch,
+
+  // Constants
+  constants,
+
+  // Internal: for initialization
+  _metadataCache: metadataCache,
+  _contentCache: contentCache,
+
+  // Initialize the caches by fetching the full tree from server
+  async _init(basePath) {
+    const tree = await transport.fetchTree(basePath);
+    metadataCache.populate(tree);
+    console.log(`[shim:fs] Initialized with ${metadataCache.size} entries`);
+  },
+};