launch-context.ts

import type { Dictionary } from '@crawlee/types';
import type { BrowserFingerprintWithHeaders } from 'fingerprint-generator';
import type { BrowserPlugin, CommonBrowser, CommonLibrary } from './abstract-classes/browser-plugin';
import type { UnwrapPromise } from './utils';

/**
 * `LaunchContext` holds information about the launched browser. It's useful
 * to retrieve the `launchOptions`, the proxy the browser was launched with
 * or any other information user chose to add to the `LaunchContext` by calling
 * its `extend` function. This is very useful to keep track of browser-scoped
 * values, such as session IDs.
 */
export interface LaunchContextOptions<
    Library extends CommonLibrary = CommonLibrary,
    LibraryOptions extends Dictionary | undefined = Parameters<Library['launch']>[0],
    LaunchResult extends CommonBrowser = UnwrapPromise<ReturnType<Library['launch']>>,
    NewPageOptions = Parameters<LaunchResult['newPage']>[0],
    NewPageResult = UnwrapPromise<ReturnType<LaunchResult['newPage']>>,
> {
    /**
     * To make identification of `LaunchContext` easier, `BrowserPool` assigns
     * the `LaunchContext` an `id` that's equal to the `id` of the page that
     * triggered the browser launch. This is useful, because many pages share
     * a single launch context (single browser).
     */
    id?: string;
    /**
     * The `BrowserPlugin` instance used to launch the browser.
     */
    browserPlugin: BrowserPlugin<Library, LibraryOptions, LaunchResult, NewPageOptions, NewPageResult>;
    /**
     * The actual options the browser was launched with, after changes.
     * Those changes would be typically made in pre-launch hooks.
     */
    launchOptions: LibraryOptions;
    /**
     * By default pages share the same browser context.
     * If set to `true` each page uses its own context that is destroyed once the page is closed or crashes.
     */
    useIncognitoPages?: boolean;
    /**
     * @experimental
     * Like `useIncognitoPages`, but for persistent contexts, so cache is used for faster loading.
     * Works best with Firefox. Unstable on Chromium.
     */
    experimentalContainers?: boolean;
    /**
     * Path to a User Data Directory, which stores browser session data like cookies and local storage.
     */
    userDataDir?: string;
    proxyUrl?: string;
}

export class LaunchContext<
    Library extends CommonLibrary = CommonLibrary,
    LibraryOptions extends Dictionary | undefined = Parameters<Library['launch']>[0],
    LaunchResult extends CommonBrowser = UnwrapPromise<ReturnType<Library['launch']>>,
    NewPageOptions = Parameters<LaunchResult['newPage']>[0],
    NewPageResult = UnwrapPromise<ReturnType<LaunchResult['newPage']>>,
> {
    id?: string;
    browserPlugin: BrowserPlugin<Library, LibraryOptions, LaunchResult, NewPageOptions, NewPageResult>;
    launchOptions: LibraryOptions;
    useIncognitoPages: boolean;
    experimentalContainers: boolean;
    userDataDir: string;

    private _proxyUrl?: string;
    private readonly _reservedFieldNames = [...Reflect.ownKeys(this), 'extend'];

    fingerprint?: BrowserFingerprintWithHeaders;
    [K: PropertyKey]: unknown;

    constructor(options: LaunchContextOptions<Library, LibraryOptions, LaunchResult, NewPageOptions, NewPageResult>) {
        const {
            id,
            browserPlugin,
            launchOptions,
            proxyUrl,
            useIncognitoPages,
            experimentalContainers,
            userDataDir = '',
        } = options;

        this.id = id;
        this.browserPlugin = browserPlugin;
        this.launchOptions = launchOptions;
        this.useIncognitoPages = useIncognitoPages ?? false;
        this.experimentalContainers = experimentalContainers ?? false;
        this.userDataDir = userDataDir;

        this._proxyUrl = proxyUrl;
    }

    /**
     * Extend the launch context with any extra fields.
     * This is useful to keep state information relevant
     * to the browser being launched. It ensures that
     * no internal fields are overridden and should be
     * used instead of property assignment.
     */
    extend<T extends Record<PropertyKey, unknown>>(fields: T): void {
        Object.entries(fields).forEach(([key, value]) => {
            if (this._reservedFieldNames.includes(key)) {
                throw new Error(`Cannot extend LaunchContext with key: ${key}, because it's reserved.`);
            } else {
                Reflect.set(this, key, value);
            }
        });
    }

    /**
     * Sets a proxy URL for the browser.
     * Use `undefined` to unset existing proxy URL.
     */
    set proxyUrl(url: string | undefined) {
        if (!url) {
            return;
        }

        const urlInstance = new URL(url);
        urlInstance.pathname = '/';
        urlInstance.search = '';
        urlInstance.hash = '';

        // https://www.chromium.org/developers/design-documents/network-settings/#command-line-options-for-proxy-settings
        this._proxyUrl = urlInstance.href.slice(0, -1);
    }

    /**
     * Returns the proxy URL of the browser.
     */
    get proxyUrl(): string | undefined {
        return this._proxyUrl;
    }
}