feat: add DockerSandbox class for container lifecycle

src/sandbox/docker.ts

@@ -0,0 +1,123 @@
+import { execFile } from 'child_process';
+
+export interface DockerSandboxConfig {
+  sessionId: string;
+  image: string;
+  workspaceDir: string;
+  network: 'none' | 'bridge' | 'host';
+  memoryLimit: string;
+  cpuLimit: string;
+  timeoutSeconds: number;
+}
+
+export interface ExecOptions {
+  cwd?: string;
+  timeout?: number;
+}
+
+export interface ExecResult {
+  stdout: string;
+  stderr: string;
+}
+
+/**
+ * Manages a single Docker container for sandboxed tool execution.
+ * Uses the Docker CLI directly (no SDK dependency).
+ */
+export class DockerSandbox {
+  private config: DockerSandboxConfig;
+  private _containerId: string | null = null;
+  private _hostWorkdir: string;
+
+  constructor(config: DockerSandboxConfig) {
+    this.config = config;
+    const sanitizedId = config.sessionId.replace(/[^a-zA-Z0-9_-]/g, '_');
+    this._hostWorkdir = `/tmp/flynn-sandbox-${sanitizedId}`;
+  }
+
+  get containerId(): string | null {
+    return this._containerId;
+  }
+
+  get containerName(): string {
+    const sanitizedId = this.config.sessionId.replace(/[^a-zA-Z0-9_-]/g, '_');
+    return `flynn-${sanitizedId}`;
+  }
+
+  /** Create and start the sandbox container. */
+  async create(): Promise<void> {
+    const args = [
+      'create',
+      '--name', this.containerName,
+      '--memory', this.config.memoryLimit,
+      '--cpus', this.config.cpuLimit,
+      '--network', this.config.network,
+      '-v', `${this._hostWorkdir}:${this.config.workspaceDir}`,
+      this.config.image,
+      'sleep', 'infinity',
+    ];
+
+    const createResult = await this.dockerCmd(args);
+    this._containerId = createResult.stdout.trim();
+
+    await this.dockerCmd(['start', this._containerId]);
+  }
+
+  /** Execute a command inside the container. */
+  async exec(command: string, opts?: ExecOptions): Promise<ExecResult> {
+    if (!this._containerId) {
+      throw new Error('Sandbox container not created. Call create() first.');
+    }
+
+    const args = ['exec'];
+    if (opts?.cwd) {
+      args.push('-w', opts.cwd);
+    }
+    args.push(this._containerId, 'bash', '-c', command);
+
+    const timeout = opts?.timeout ?? this.config.timeoutSeconds * 1000;
+    return this.dockerCmd(args, timeout);
+  }
+
+  /** Force-remove the container. */
+  async destroy(): Promise<void> {
+    if (!this._containerId) return;
+
+    try {
+      await this.dockerCmd(['rm', '-f', this._containerId]);
+    } catch {
+      // Ignore errors during cleanup
+    }
+    this._containerId = null;
+  }
+
+  /** Check if Docker is available on this host. */
+  static async isAvailable(): Promise<boolean> {
+    try {
+      await new Promise<string>((resolve, reject) => {
+        execFile('docker', ['version', '--format', '{{.Server.Version}}'], {
+          timeout: 5000,
+        }, (error, stdout) => {
+          if (error) reject(error);
+          else resolve(stdout);
+        });
+      });
+      return true;
+    } catch {
+      return false;
+    }
+  }
+
+  /** Run a docker CLI command. */
+  private dockerCmd(args: string[], timeout = 30_000): Promise<ExecResult> {
+    return new Promise((resolve, reject) => {
+      execFile('docker', args, { timeout, maxBuffer: 1024 * 1024 }, (error, stdout, stderr) => {
+        if (error) {
+          reject(error);
+          return;
+        }
+        resolve({ stdout, stderr });
+      });
+    });
+  }
+}