import { fileURLToPath } from 'node:url';
import { z } from 'zod';
import type { BrowserContextFactory } from './browser-context-factory.js';
import type { FullConfig } from './config.js';
import { Context } from './context.js';
import type * as mcpServer from './mcp/server.js';
import { Response } from './response.js';
import { SessionLog } from './session-log.js';
import type { AnyTool } from './tools/tool.js';
import { defineTool } from './tools/tool.js';
import { filteredTools } from './tools.js';
import { browserServerBackendDebug, logUnhandledError } from './utils/log.js';
import { packageJSON } from './utils/package.js';
type NonEmptyArray<T> = [T, ...T[]];
export type FactoryList = NonEmptyArray<BrowserContextFactory>;
export class BrowserServerBackend implements mcpServer.ServerBackend {
name = 'Playwright';
version = packageJSON.version;
private readonly _tools: AnyTool[];
private _context: Context | undefined;
private _sessionLog: SessionLog | undefined;
private readonly _config: FullConfig;
private _browserContextFactory: BrowserContextFactory;
constructor(config: FullConfig, factories: FactoryList) {
this._config = config;
this._browserContextFactory = factories[0];
this._tools = filteredTools(config);
if (factories.length > 1) {
this._tools.push(this._defineContextSwitchTool(factories));
}
}
async initialize(server: mcpServer.Server): Promise<void> {
const capabilities =
server.getClientCapabilities() as mcpServer.ClientCapabilities;
let rootPath: string | undefined;
if (
capabilities.roots &&
(server.getClientVersion()?.name === 'Visual Studio Code' ||
server.getClientVersion()?.name === 'Visual Studio Code - Insiders')
) {
const { roots } = await server.listRoots();
const firstRootUri = roots[0]?.uri;
const url = firstRootUri ? new URL(firstRootUri) : undefined;
rootPath = url ? fileURLToPath(url) : undefined;
}
this._sessionLog = this._config.saveSession
? await SessionLog.create(this._config, rootPath)
: undefined;
this._context = new Context({
tools: this._tools,
config: this._config,
browserContextFactory: this._browserContextFactory,
sessionLog: this._sessionLog,
clientInfo: { ...server.getClientVersion(), rootPath },
});
}
tools(): mcpServer.ToolSchema[] {
return this._tools.map((tool) => tool.schema);
}
async callTool(
schema: mcpServer.ToolSchema,
rawArguments: Record<string, unknown> | undefined
) {
if (!this._context) {
throw new Error('Context not initialized. Call initialize() first.');
}
const context = this._context;
const parsedArguments = schema.inputSchema.parse(rawArguments || {});
const response = new Response(
context,
schema.name,
parsedArguments,
parsedArguments.expectation
);
const matchedTool = this._tools.find((t) => t.schema.name === schema.name);
if (!matchedTool) {
throw new Error(`Tool not found: ${schema.name}`);
}
context.setRunningTool(true);
browserServerBackendDebug(`Executing tool: ${schema.name}`);
try {
await matchedTool.handle(context, parsedArguments, response);
await response.finish();
this._sessionLog?.logResponse(response);
browserServerBackendDebug(`Tool ${schema.name} completed successfully`);
} catch (error: unknown) {
browserServerBackendDebug(`Error executing tool ${schema.name}:`, error);
response.addError(String(error));
} finally {
context.setRunningTool(false);
}
return response.serialize();
}
serverClosed() {
this._context?.dispose().catch(logUnhandledError);
}
private _defineContextSwitchTool(factories: FactoryList): AnyTool {
const self = this;
return defineTool({
capability: 'core',
schema: {
name: 'browser_connect',
title: 'Connect to a browser context',
description: [
'Connect to a browser using one of the available methods:',
...factories.map(
(factory) => `- "${factory.name}": ${factory.description}`
),
].join('\n'),
inputSchema: z.object({
method: z
.enum(factories.map((f) => f.name) as [string, ...string[]])
.default(factories[0].name)
.describe('The method to use to connect to the browser'),
}),
type: 'readOnly',
},
async handle(_context, params, response) {
const selectedFactory = factories.find((f) => f.name === params.method);
if (!selectedFactory) {
response.addError(`Unknown connection method: ${params.method}`);
return;
}
await self._setContextFactory(selectedFactory);
response.addResult('Successfully changed connection method.');
},
});
}
private async _setContextFactory(newFactory: BrowserContextFactory) {
if (this._context) {
const options = {
...this._context.options,
browserContextFactory: newFactory,
};
await this._context.dispose();
this._context = new Context(options);
}
this._browserContextFactory = newFactory;
}
}
