import { type Browser, type BrowserContext, chromium } from 'playwright';
import type {
BrowserContextFactory,
ClientInfo,
} from '../browser-context-factory.js';
import { startHttpServer } from '../http-server.js';
import { extensionContextFactoryDebug } from '../utils/log.js';
import { CDPRelayServer } from './cdp-relay.js';
export class ExtensionContextFactory implements BrowserContextFactory {
name = 'extension';
description = 'Connect to a browser using the Playwright MCP extension';
private readonly _browserChannel: string;
private _relayPromise: Promise<CDPRelayServer> | undefined;
private _browserPromise: Promise<Browser> | undefined;
constructor(browserChannel: string, _userDataDir?: string) {
this._browserChannel = browserChannel;
}
async createContext(
clientInfo: ClientInfo,
abortSignal: AbortSignal
): Promise<{
browserContext: BrowserContext;
close: () => Promise<void>;
}> {
// First call will establish the connection to the extension.
this._browserPromise ??= this._obtainBrowser(clientInfo, abortSignal);
const browser = await this._browserPromise;
return {
browserContext: browser.contexts()[0],
close: async () => {
extensionContextFactoryDebug('close() called for browser context');
await browser.close();
this._browserPromise = undefined;
},
};
}
private async _obtainBrowser(
clientInfo: ClientInfo,
abortSignal: AbortSignal
): Promise<Browser> {
this._relayPromise ??= this._startRelay(abortSignal);
const relay = await this._relayPromise;
abortSignal.throwIfAborted();
await relay.ensureExtensionConnectionForMCPContext(clientInfo, abortSignal);
const browser = await chromium.connectOverCDP(relay.cdpEndpoint());
browser.on('disconnected', () => {
this._browserPromise = undefined;
extensionContextFactoryDebug('Browser disconnected');
});
return browser;
}
private async _startRelay(abortSignal: AbortSignal) {
const httpServer = await startHttpServer({});
const cdpRelayServer = new CDPRelayServer(httpServer, this._browserChannel);
extensionContextFactoryDebug(
`CDP relay server started, extension endpoint: ${cdpRelayServer.extensionEndpoint()}.`
);
if (abortSignal.aborted) {
cdpRelayServer.stop();
} else {
abortSignal.addEventListener('abort', () => cdpRelayServer.stop());
}
return cdpRelayServer;
}
}
