Read and write files through Zed (#6169)

Co-authored-by: Agus Zubiaga <agus@zed.dev>

packages/cli/src/zed-integration/fileSystemService.ts

@@ -0,0 +1,47 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { FileSystemService } from '@google/gemini-cli-core';
+import * as acp from './acp.js';
+
+/**
+ * ACP client-based implementation of FileSystemService
+ */
+export class AcpFileSystemService implements FileSystemService {
+  constructor(
+    private readonly client: acp.Client,
+    private readonly sessionId: string,
+    private readonly capabilities: acp.FileSystemCapability,
+    private readonly fallback: FileSystemService,
+  ) {}
+
+  async readTextFile(filePath: string): Promise<string> {
+    if (!this.capabilities.readTextFile) {
+      return this.fallback.readTextFile(filePath);
+    }
+
+    const response = await this.client.readTextFile({
+      path: filePath,
+      sessionId: this.sessionId,
+      line: null,
+      limit: null,
+    });
+
+    return response.content;
+  }
+
+  async writeTextFile(filePath: string, content: string): Promise<void> {
+    if (!this.capabilities.writeTextFile) {
+      return this.fallback.writeTextFile(filePath, content);
+    }
+
+    await this.client.writeTextFile({
+      path: filePath,
+      content,
+      sessionId: this.sessionId,
+    });
+  }
+}