implement fs shims

shims/fs/content-cache.js

@@ -0,0 +1,91 @@
+// In-memory content cache with simple LRU eviction
+// Stores file content fetched from the server.
+
+const DEFAULT_MAX_SIZE = 50 * 1024 * 1024; // 50 MB
+
+export class ContentCache {
+  constructor(maxSize = DEFAULT_MAX_SIZE) {
+    this._cache = new Map(); // path -> { data, size, accessedAt }
+    this._currentSize = 0;
+    this._maxSize = maxSize;
+  }
+
+  has(path) {
+    return this._cache.has(this._normalize(path));
+  }
+
+  get(path) {
+    const entry = this._cache.get(this._normalize(path));
+    if (entry) {
+      entry.accessedAt = Date.now();
+      return entry.data;
+    }
+    return null;
+  }
+
+  set(path, data) {
+    const norm = this._normalize(path);
+    const size = data ? data.length || data.byteLength || 0 : 0;
+
+    // Remove old entry if replacing
+    if (this._cache.has(norm)) {
+      this._currentSize -= this._cache.get(norm).size;
+    }
+
+    // Evict LRU entries if needed
+    while (this._currentSize + size > this._maxSize && this._cache.size > 0) {
+      this._evictOne();
+    }
+
+    this._cache.set(norm, { data, size, accessedAt: Date.now() });
+    this._currentSize += size;
+  }
+
+  delete(path) {
+    const norm = this._normalize(path);
+    const entry = this._cache.get(norm);
+    if (entry) {
+      this._currentSize -= entry.size;
+      this._cache.delete(norm);
+    }
+  }
+
+  // Invalidate a path (remove from cache so next read fetches fresh)
+  invalidate(path) {
+    this.delete(path);
+  }
+
+  clear() {
+    this._cache.clear();
+    this._currentSize = 0;
+  }
+
+  get size() {
+    return this._cache.size;
+  }
+
+  get currentBytes() {
+    return this._currentSize;
+  }
+
+  _evictOne() {
+    let oldest = null;
+    let oldestTime = Infinity;
+    for (const [key, entry] of this._cache) {
+      if (entry.accessedAt < oldestTime) {
+        oldest = key;
+        oldestTime = entry.accessedAt;
+      }
+    }
+    if (oldest) {
+      this.delete(oldest);
+    }
+  }
+
+  _normalize(p) {
+    return (p || "")
+      .replace(/\\/g, "/")
+      .replace(/^\/+/, "")
+      .replace(/\/+$/, "");
+  }
+}