chore: extract pure mcp server helpers (#751)

src/browserServerBackend.ts

@@ -0,0 +1,66 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { FullConfig } from './config.js';
+import { Context } from './context.js';
+import { logUnhandledError } from './log.js';
+import { Response } from './response.js';
+import { SessionLog } from './sessionLog.js';
+import { filteredTools } from './tools.js';
+import { packageJSON } from './package.js';
+
+import type { BrowserContextFactory } from './browserContextFactory.js';
+import type * as mcpServer from './mcp/server.js';
+import type { ServerBackend } from './mcp/server.js';
+import type { Tool } from './tools/tool.js';
+
+export class BrowserServerBackend implements ServerBackend {
+  name = 'Playwright';
+  version = packageJSON.version;
+  private _tools: Tool[];
+  private _context: Context;
+  private _sessionLog: SessionLog | undefined;
+
+  constructor(config: FullConfig, browserContextFactory: BrowserContextFactory) {
+    this._tools = filteredTools(config);
+    this._context = new Context(this._tools, config, browserContextFactory);
+  }
+
+  async initialize() {
+    this._sessionLog = this._context.config.saveSession ? await SessionLog.create(this._context.config) : undefined;
+  }
+
+  tools(): mcpServer.ToolSchema<any>[] {
+    return this._tools.map(tool => tool.schema);
+  }
+
+  async callTool(schema: mcpServer.ToolSchema<any>, parsedArguments: any) {
+    const response = new Response(this._context, schema.name, parsedArguments);
+    const tool = this._tools.find(tool => tool.schema.name === schema.name)!;
+    await tool.handle(this._context, parsedArguments, response);
+    if (this._sessionLog)
+      await this._sessionLog.log(response);
+    return await response.serialize();
+  }
+
+  serverInitialized(version: mcpServer.ClientVersion | undefined) {
+    this._context.clientVersion = version;
+  }
+
+  serverClosed() {
+    void this._context.dispose().catch(logUnhandledError);
+  }
+}