parcer/server/src/browser-management/classes/RemoteBrowser.ts

import {
    Page,
    Browser,
    CDPSession,
    BrowserContext,
} from 'playwright';
import { Socket } from "socket.io";
import { chromium } from 'playwright-extra';
import stealthPlugin from 'puppeteer-extra-plugin-stealth';
import { PlaywrightBlocker } from '@cliqz/adblocker-playwright';
import fetch from 'cross-fetch';
import { throttle } from 'lodash';
import sharp from 'sharp';

import logger from '../../logger';
import { InterpreterSettings, RemoteBrowserOptions } from "../../types";
import { WorkflowGenerator } from "../../workflow-management/classes/Generator";
import { WorkflowInterpreter } from "../../workflow-management/classes/Interpreter";
import { getDecryptedProxyConfig } from '../../routes/proxy';
import { getInjectableScript } from 'idcac-playwright';

chromium.use(stealthPlugin());

const MEMORY_CONFIG = {
    gcInterval: 60000, // 1 minute
    maxHeapSize: 2048 * 1024 * 1024, // 2GB
    heapUsageThreshold: 0.85 // 85%
};

const SCREENCAST_CONFIG: {
    format: "jpeg" | "png";
    maxWidth: number;
    maxHeight: number;
    targetFPS: number;
    compressionQuality: number;
    maxQueueSize: number;
} = {
    format: 'png',
    maxWidth: 1280,
    maxHeight: 720,
    targetFPS: 30,
    compressionQuality: 0.95,
    maxQueueSize: 2
};

/**
 * This class represents a remote browser instance.
 * It is used to allow a variety of interaction with the Playwright's browser instance.
 * Every remote browser holds an instance of a generator and interpreter classes with
 * the purpose of generating and interpreting workflows.
 * @category BrowserManagement
 */
export class RemoteBrowser {

    /**
     * Playwright's [browser](https://playwright.dev/docs/api/class-browser) instance.
     * @private
     */
    private browser: Browser | null = null;

    private context: BrowserContext | null = null;

    /**
     * The Playwright's [CDPSession](https://playwright.dev/docs/api/class-cdpsession) instance,
     * used to talk raw Chrome Devtools Protocol.
     * @private
     */
    private client: CDPSession | null | undefined = null;

    /**
     * Socket.io socket instance enabling communication with the client (frontend) side.
     * @private
     */
    private socket: Socket;

    /**
     * The Playwright's [Page](https://playwright.dev/docs/api/class-page) instance
     * as current interactive remote browser's page.
     * @private
     */
    private currentPage: Page | null | undefined = null;

    /**
     * Interpreter settings for any started interpretation.
     * @private
     */
    private interpreterSettings: InterpreterSettings = {
        debug: false,
        maxConcurrency: 1,
        maxRepeats: 1,
    };

    /**
     * The user ID that owns this browser instance
     * @private
     */
    private userId: string;

    private lastEmittedUrl: string | null = null;

    /**
     * {@link WorkflowGenerator} instance specific to the remote browser.
     */
    public generator: WorkflowGenerator;

    /**
     * {@link WorkflowInterpreter} instance specific to the remote browser.
     */
    public interpreter: WorkflowInterpreter;


    private screenshotQueue: Buffer[] = [];
    private isProcessingScreenshot = false;
    private screencastInterval: NodeJS.Timeout | null = null
    private isScreencastActive: boolean = false;

    /**
     * Initializes a new instances of the {@link Generator} and {@link WorkflowInterpreter} classes and
     * assigns the socket instance everywhere.
     * @param socket socket.io socket instance used to communicate with the client side
     * @constructor
     */
    public constructor(socket: Socket, userId: string) {
        this.socket = socket;
        this.userId = userId;
        this.interpreter = new WorkflowInterpreter(socket);
        this.generator = new WorkflowGenerator(socket);
    }

    private initializeMemoryManagement(): void {
        setInterval(() => {
            const memoryUsage = process.memoryUsage();
            const heapUsageRatio = memoryUsage.heapUsed / MEMORY_CONFIG.maxHeapSize;

            if (heapUsageRatio > MEMORY_CONFIG.heapUsageThreshold) {
                logger.warn('High memory usage detected, triggering cleanup');
                this.performMemoryCleanup();
            }

            // Clear screenshot queue if it's too large
            if (this.screenshotQueue.length > SCREENCAST_CONFIG.maxQueueSize) {
                this.screenshotQueue = this.screenshotQueue.slice(-SCREENCAST_CONFIG.maxQueueSize);
            }
        }, MEMORY_CONFIG.gcInterval);
    }

    private async performMemoryCleanup(): Promise<void> {
        this.screenshotQueue = [];
        this.isProcessingScreenshot = false;

        if (global.gc) {
            global.gc();
        }

        // Reset CDP session if needed
        if (this.client) {
            try {
                await this.stopScreencast();
                this.client = null;
                if (this.currentPage) {
                    this.client = await this.currentPage.context().newCDPSession(this.currentPage);
                    await this.startScreencast();
                }
            } catch (error) {
                logger.error('Error resetting CDP session:', error);
            }
        }
    }

    /**
     * Normalizes URLs to prevent navigation loops while maintaining consistent format
     */
    private normalizeUrl(url: string): string {
        try {
            const parsedUrl = new URL(url);
            // Remove trailing slashes except for root path
            parsedUrl.pathname = parsedUrl.pathname.replace(/\/+$/, '') || '/';
            // Ensure consistent protocol handling
            parsedUrl.protocol = parsedUrl.protocol.toLowerCase();
            return parsedUrl.toString();
        } catch {
            return url;
        }
    }

    /**
     * Determines if a URL change is significant enough to emit
     */
    private shouldEmitUrlChange(newUrl: string): boolean {
        if (!this.lastEmittedUrl) {
            return true;
        }
        const normalizedNew = this.normalizeUrl(newUrl);
        const normalizedLast = this.normalizeUrl(this.lastEmittedUrl);
        return normalizedNew !== normalizedLast;
    }

    private async setupPageEventListeners(page: Page) {
        page.on('framenavigated', async (frame) => {
            if (frame === page.mainFrame()) {
                const currentUrl = page.url();
                if (this.shouldEmitUrlChange(currentUrl)) {
                    this.lastEmittedUrl = currentUrl;
                    this.socket.emit('urlChanged', {url: currentUrl, userId: this.userId});
                }
            }
        });

        // Handle page load events with retry mechanism
        page.on('load', async () => {
            const injectScript = async (): Promise<boolean> => {
                try {
                    await page.waitForLoadState('networkidle', { timeout: 5000 });

                    await page.evaluate(getInjectableScript());
                    return true;
                } catch (error: any) {
                    logger.log('warn', `Script injection attempt failed: ${error.message}`);
                    return false;
                }
            };

            const success = await injectScript();
            console.log("Script injection result:", success);
        });
    }

    private getUserAgent() {
        const userAgents = [
            'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.5845.140 Safari/537.36',
            'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:117.0) Gecko/20100101 Firefox/117.0',
            'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.1938.81 Safari/537.36 Edg/116.0.1938.81',
            'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.5845.96 Safari/537.36 OPR/101.0.4843.25',
            'Mozilla/5.0 (Windows NT 11.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.5938.62 Safari/537.36',
            'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:118.0) Gecko/20100101 Firefox/118.0',
        ];

        return userAgents[Math.floor(Math.random() * userAgents.length)];
    }

    /**
     * An asynchronous constructor for asynchronously initialized properties.
     * Must be called right after creating an instance of RemoteBrowser class.
     * @param options remote browser options to be used when launching the browser
     * @returns {Promise<void>}
     */
    public initialize = async (userId: string): Promise<void> => {
        this.browser = <Browser>(await chromium.launch({
            headless: true,
            args: [
                "--disable-blink-features=AutomationControlled",
                "--disable-web-security",
                "--disable-features=IsolateOrigins,site-per-process",
                "--disable-site-isolation-trials",
                "--disable-extensions",
                "--no-sandbox",
                "--disable-dev-shm-usage",
                "--force-color-profile=srgb",
                "--force-device-scale-factor=2",
            ],
        }));
        const proxyConfig = await getDecryptedProxyConfig(userId);
        let proxyOptions: { server: string, username?: string, password?: string } = { server: '' };
        if (proxyConfig.proxy_url) {
            proxyOptions = {
                server: proxyConfig.proxy_url,
                ...(proxyConfig.proxy_username && proxyConfig.proxy_password && {
                    username: proxyConfig.proxy_username,
                    password: proxyConfig.proxy_password,
                }),
            };
        }
        const contextOptions: any = {
            // viewport: { height: 400, width: 900 },
            // recordVideo: { dir: 'videos/' }
            // Force reduced motion to prevent animation issues
            reducedMotion: 'reduce',
            // Force JavaScript to be enabled
            javaScriptEnabled: true,
            // Set a reasonable timeout
            timeout: 50000,
            // Disable hardware acceleration
            forcedColors: 'none',
            isMobile: false,
            hasTouch: false,
            userAgent: this.getUserAgent(),
            deviceScaleFactor: 2,
        };

        if (proxyOptions.server) {
            contextOptions.proxy = {
                server: proxyOptions.server,
                username: proxyOptions.username ? proxyOptions.username : undefined,
                password: proxyOptions.password ? proxyOptions.password : undefined,
            };
        }

        this.context = await this.browser.newContext(contextOptions);
        await this.context.addInitScript(
            `const defaultGetter = Object.getOwnPropertyDescriptor(
              Navigator.prototype,
              "webdriver"
            ).get;
            defaultGetter.apply(navigator);
            defaultGetter.toString();
            Object.defineProperty(Navigator.prototype, "webdriver", {
              set: undefined,
              enumerable: true,
              configurable: true,
              get: new Proxy(defaultGetter, {
                apply: (target, thisArg, args) => {
                  Reflect.apply(target, thisArg, args);
                  return false;
                },
              }),
            });
            const patchedGetter = Object.getOwnPropertyDescriptor(
              Navigator.prototype,
              "webdriver"
            ).get;
            patchedGetter.apply(navigator);
            patchedGetter.toString();`
        );
        this.currentPage = await this.context.newPage();

        await this.setupPageEventListeners(this.currentPage);

        const viewportSize = await this.currentPage.viewportSize();
        if (viewportSize) {
            this.socket.emit('viewportInfo', {
                width: viewportSize.width,
                height: viewportSize.height,
                userId: this.userId
            });
        }

        try {
            const blocker = await PlaywrightBlocker.fromLists(fetch, ['https://easylist.to/easylist/easylist.txt']);
            await blocker.enableBlockingInPage(this.currentPage);
            this.client = await this.currentPage.context().newCDPSession(this.currentPage);
            await blocker.disableBlockingInPage(this.currentPage);
            console.log('Adblocker initialized');
        } catch (error: any) {
            console.warn('Failed to initialize adblocker, continuing without it:', error.message);
            // Still need to set up the CDP session even if blocker fails
            this.client = await this.currentPage.context().newCDPSession(this.currentPage);
        }
    };

    public updateViewportInfo = async (): Promise<void> => {
        if (this.currentPage) {
            const viewportSize = await this.currentPage.viewportSize();
            if (viewportSize) {
                this.socket.emit('viewportInfo', {
                    width: viewportSize.width,
                    height: viewportSize.height,
                    userId: this.userId
                });
            }
        }
    };

    /**
     * Registers all event listeners needed for the recording editor session.
     * Should be called only once after the full initialization of the remote browser.
     * @returns void
     */
    public registerEditorEvents = (): void => {
        // For each event, include userId to make sure events are handled for the correct browser
        logger.log('debug', `Registering editor events for user: ${this.userId}`);
        
        // Listen for specific events for this user
        this.socket.on(`rerender:${this.userId}`, async () => {
            logger.debug(`Rerender event received for user ${this.userId}`);
            await this.makeAndEmitScreenshot();
        });
        
        // For backward compatibility, also listen to the general event
        this.socket.on('rerender', async () => {
            logger.debug(`General rerender event received, checking if for user ${this.userId}`);
            await this.makeAndEmitScreenshot();
        });
        
        this.socket.on(`settings:${this.userId}`, (settings) => {
            this.interpreterSettings = settings;
            logger.debug(`Settings updated for user ${this.userId}`);
        });
        
        this.socket.on(`changeTab:${this.userId}`, async (tabIndex) => {
            logger.debug(`Tab change to ${tabIndex} requested for user ${this.userId}`);
            await this.changeTab(tabIndex);
        });
        
        this.socket.on(`addTab:${this.userId}`, async () => {
            logger.debug(`New tab requested for user ${this.userId}`);
            await this.currentPage?.context().newPage();
            const lastTabIndex = this.currentPage ? this.currentPage.context().pages().length - 1 : 0;
            await this.changeTab(lastTabIndex);
        });
        
        this.socket.on(`closeTab:${this.userId}`, async (tabInfo) => {
            logger.debug(`Close tab ${tabInfo.index} requested for user ${this.userId}`);
            const page = this.currentPage?.context().pages()[tabInfo.index];
            if (page) {
                if (tabInfo.isCurrent) {
                    if (this.currentPage?.context().pages()[tabInfo.index + 1]) {
                        // next tab
                        await this.changeTab(tabInfo.index + 1);
                    } else {
                        //previous tab
                        await this.changeTab(tabInfo.index - 1);
                    }
                }
                await page.close();
                logger.log(
                    'debug',
                    `Tab ${tabInfo.index} was closed for user ${this.userId}, new tab count: ${this.currentPage?.context().pages().length}`
                );
            } else {
                logger.log('error', `Tab index ${tabInfo.index} out of range for user ${this.userId}`);
            }
        });
        
        this.socket.on(`setViewportSize:${this.userId}`, async (data: { width: number, height: number }) => {
            const { width, height } = data;
            logger.log('debug', `Viewport size change to width=${width}, height=${height} requested for user ${this.userId}`);

            // Update the browser context's viewport dynamically
            if (this.context && this.browser) {
                this.context = await this.browser.newContext({ viewport: { width, height } });
                logger.log('debug', `Viewport size updated to width=${width}, height=${height} for user ${this.userId}`);
            }
        });
        
        // For backward compatibility, also register the standard events
        this.socket.on('settings', (settings) => this.interpreterSettings = settings);
        this.socket.on('changeTab', async (tabIndex) => await this.changeTab(tabIndex));
        this.socket.on('addTab', async () => {
            await this.currentPage?.context().newPage();
            const lastTabIndex = this.currentPage ? this.currentPage.context().pages().length - 1 : 0;
            await this.changeTab(lastTabIndex);
        });
        this.socket.on('closeTab', async (tabInfo) => {
            const page = this.currentPage?.context().pages()[tabInfo.index];
            if (page) {
                if (tabInfo.isCurrent) {
                    if (this.currentPage?.context().pages()[tabInfo.index + 1]) {
                        await this.changeTab(tabInfo.index + 1);
                    } else {
                        await this.changeTab(tabInfo.index - 1);
                    }
                }
                await page.close();
            }
        });
        this.socket.on('setViewportSize', async (data: { width: number, height: number }) => {
            const { width, height } = data;
            if (this.context && this.browser) {
                this.context = await this.browser.newContext({ viewport: { width, height } });
            }
        });
    };
    /**
     * Subscribes the remote browser for a screencast session
     * on [CDP](https://chromedevtools.github.io/devtools-protocol/) level,
     * where screenshot is being sent through the socket
     * every time the browser's active page updates.
     * @returns {Promise<void>}
     */
    public subscribeToScreencast = async (): Promise<void> => {
        logger.log('debug', `Starting screencast for user: ${this.userId}`);
        await this.startScreencast();
        if (!this.client) {
            logger.log('warn', 'client is not initialized');
            return;
        }
        // Set flag to indicate screencast is active
        this.isScreencastActive = true;

        await this.updateViewportInfo();

        this.client.on('Page.screencastFrame', ({ data: base64, sessionId }) => {
            // Only process if screencast is still active for this user
            if (!this.isScreencastActive) {
                return;
            }
            this.emitScreenshot(Buffer.from(base64, 'base64'))
            setTimeout(async () => {
                try {
                    if (!this.client || !this.isScreencastActive) {
                        logger.log('warn', 'client is not initialized');
                        return;
                    }
                    await this.client.send('Page.screencastFrameAck', { sessionId: sessionId });
                } catch (e: any) {
                    logger.log('error', `Screencast error: ${e}`);
                }
            }, 100);
        });
    };

    /**
     * Terminates the screencast session and closes the remote browser.
     * If an interpretation was running it will be stopped.
     * @returns {Promise<void>}
     */
    public async switchOff(): Promise<void> {
        try {
            this.isScreencastActive = false;

            await this.interpreter.stopInterpretation();

            if (this.screencastInterval) {
                clearInterval(this.screencastInterval);
            }

            if (this.client) {
                await this.stopScreencast();
            }

            if (this.browser) {
                await this.browser.close();
            }

            this.screenshotQueue = [];
            //this.performanceMonitor.reset();

        } catch (error) {
            logger.error('Error during browser shutdown:', error);
        }
    }

    private async optimizeScreenshot(screenshot: Buffer): Promise<Buffer> {
        try {
            return await sharp(screenshot)
                .png({
                    quality: Math.round(SCREENCAST_CONFIG.compressionQuality * 100),                
                    compressionLevel: 3,        
                    adaptiveFiltering: true,    
                    force: true                
                })
                .resize({
                    width: SCREENCAST_CONFIG.maxWidth,
                    height: SCREENCAST_CONFIG.maxHeight,
                    fit: 'inside',
                    withoutEnlargement: true,
                    kernel: sharp.kernel.mitchell  
                })
                .toBuffer();
        } catch (error) {
            logger.error('Screenshot optimization failed:', error);
            return screenshot;
        }
    }

    /**
     * Makes and emits a single screenshot to the client side.
     * @returns {Promise<void>}
     */
    public makeAndEmitScreenshot = async (): Promise<void> => {
        try {
            const screenshot = await this.currentPage?.screenshot();
            if (screenshot) {
                this.emitScreenshot(screenshot);
            }
        } catch (e) {
            const { message } = e as Error;
            logger.log('error', `Screenshot error: ${message}`);
        }
    };

    /**
     * Updates the active socket instance.
     * This will update all registered events for the socket and
     * all the properties using the socket.
     * @param socket socket.io socket instance used to communicate with the client side
     * @returns void
     */
    public updateSocket = (socket: Socket): void => {
        this.socket = socket;
        this.registerEditorEvents();
        this.generator?.updateSocket(socket);
        this.interpreter?.updateSocket(socket);
    };

    /**
     * Starts the interpretation of the currently generated workflow.
     * @returns {Promise<void>}
     */
    public interpretCurrentRecording = async (): Promise<void> => {
        logger.log('debug', 'Starting interpretation in the editor');
        if (this.generator) {
            const workflow = this.generator.AddGeneratedFlags(this.generator.getWorkflowFile());
            await this.initializeNewPage();
            if (this.currentPage) {
                // this.currentPage.setViewportSize({ height: 400, width: 900 });
                const params = this.generator.getParams();
                if (params) {
                    this.interpreterSettings.params = params.reduce((acc, param) => {
                        if (this.interpreterSettings.params && Object.keys(this.interpreterSettings.params).includes(param)) {
                            return { ...acc, [param]: this.interpreterSettings.params[param] };
                        } else {
                            return { ...acc, [param]: '', }
                        }
                    }, {})
                }
                logger.log('debug', `Starting interpretation with settings: ${JSON.stringify(this.interpreterSettings, null, 2)}`);
                await this.interpreter.interpretRecordingInEditor(
                    workflow, this.currentPage,
                    (newPage: Page) => this.currentPage = newPage,
                    this.interpreterSettings
                );
                // clear the active index from generator
                this.generator.clearLastIndex();
            } else {
                logger.log('error', 'Could not get a new page, returned undefined');
            }
        } else {
            logger.log('error', 'Generator is not initialized');
        }
    };

    /**
     * Stops the workflow interpretation and initializes a new page.
     * @returns {Promise<void>}
     */
    public stopCurrentInterpretation = async (): Promise<void> => {
        await this.interpreter.stopInterpretation();
        await this.initializeNewPage();
    };

    /**
     * Returns the current page instance.
     * @returns {Page | null | undefined}
     */
    public getCurrentPage = (): Page | null | undefined => {
        return this.currentPage;
    };

    /**
     * Changes the active page to the page instance on the given index
     * available in pages array on the {@link BrowserContext}.
     * Automatically stops the screencast session on the previous page and starts the new one.
     * @param tabIndex index of the page in the pages array on the {@link BrowserContext}
     * @returns {Promise<void>}
     */
    private changeTab = async (tabIndex: number): Promise<void> => {
        const page = this.currentPage?.context().pages()[tabIndex];
        if (page) {
            await this.stopScreencast();
            this.currentPage = page;

            await this.setupPageEventListeners(this.currentPage);

            //await this.currentPage.setViewportSize({ height: 400, width: 900 })
            this.client = await this.currentPage.context().newCDPSession(this.currentPage);
           // Include userId in the URL change event
            this.socket.emit('urlChanged', { 
                url: this.currentPage.url(),
                userId: this.userId
            });
            await this.makeAndEmitScreenshot();
            await this.subscribeToScreencast();
        } else {
            logger.log('error', `${tabIndex} index out of range of pages`)
        }
    }

    /**
     * Internal method for a new page initialization. Subscribes this page to the screencast.
     * @param options optional page options to be used when creating a new page
     * @returns {Promise<void>}
     */
    private initializeNewPage = async (options?: Object): Promise<void> => {
        await this.stopScreencast();
        const newPage = options ? await this.browser?.newPage(options)
            : await this.browser?.newPage();
        await newPage?.setExtraHTTPHeaders({
            'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3'
        });

        await this.currentPage?.close();
        this.currentPage = newPage;
        if (this.currentPage) {
            await this.setupPageEventListeners(this.currentPage);

            this.client = await this.currentPage.context().newCDPSession(this.currentPage);
            await this.subscribeToScreencast();
        } else {
            logger.log('error', 'Could not get a new page, returned undefined');
        }
    };

    /**
     * Initiates screencast of the remote browser through socket,
     * registers listener for rerender event and emits the loaded event.
     * Should be called only once after the browser is fully initialized.
     * @returns {Promise<void>}
     */
    private async startScreencast(): Promise<void> {
        if (!this.client) {
            logger.warn('Client is not initialized');
            return;
        }

        try {
            await this.client.send('Page.startScreencast', {
                format: SCREENCAST_CONFIG.format,
                quality: Math.round(SCREENCAST_CONFIG.compressionQuality * 100), 
                maxWidth: SCREENCAST_CONFIG.maxWidth,
                maxHeight: SCREENCAST_CONFIG.maxHeight,
            });
            // Set flag to indicate screencast is active
            this.isScreencastActive = true;

            // Set up screencast frame handler
            this.client.on('Page.screencastFrame', async ({ data, sessionId }) => {
                try {
                    const buffer = Buffer.from(data, 'base64');
                    await this.emitScreenshot(buffer);
                    await this.client?.send('Page.screencastFrameAck', { sessionId });
                } catch (error) {
                    logger.error('Screencast frame processing failed:', error);
                }
            });

            logger.info('Screencast started successfully');
        } catch (error) {
            logger.error('Failed to start screencast:', error);
        }
    }

    private async stopScreencast(): Promise<void> {
        if (!this.client) {
            logger.error('Client is not initialized');
            return;
        }

        try {
            // Set flag to indicate screencast is active
            this.isScreencastActive = false;
            await this.client.send('Page.stopScreencast');
            this.screenshotQueue = [];
            this.isProcessingScreenshot = false;
            logger.info('Screencast stopped successfully');
        } catch (error) {
            logger.error('Failed to stop screencast:', error);
        }
    }


    /**
     * Helper for emitting the screenshot of browser's active page through websocket.
     * @param payload the screenshot binary data
     * @returns void
     */
    private emitScreenshot = async (payload: Buffer, viewportSize?: { width: number, height: number }): Promise<void> => {
        if (this.isProcessingScreenshot) {
            if (this.screenshotQueue.length < SCREENCAST_CONFIG.maxQueueSize) {
                this.screenshotQueue.push(payload);
            }
            return;
        }
    
        this.isProcessingScreenshot = true;
    
        try {
            const optimizationPromise = this.optimizeScreenshot(payload);
            
            const timeoutPromise = new Promise<Buffer>((resolve) => {
                setTimeout(() => resolve(payload), 100); 
            });
            
            const optimizedScreenshot = await Promise.race([optimizationPromise, timeoutPromise]);
            const base64Data = optimizedScreenshot.toString('base64');
            const dataWithMimeType = `data:image/png;base64,${base64Data}`;
    
            this.socket.emit('screencast', {
                image: dataWithMimeType,
                userId: this.userId,
                viewport: viewportSize || await this.currentPage?.viewportSize() || null
            });
        } catch (error) {
            logger.error('Screenshot emission failed:', error);
            try {
                const base64Data = payload.toString('base64');
                const dataWithMimeType = `data:image/png;base64,${base64Data}`;
                this.socket.emit('screencast', {
                    image: dataWithMimeType,
                    userId: this.userId,
                    viewport: viewportSize || await this.currentPage?.viewportSize() || null
                });
            } catch (e) {
                logger.error('Fallback screenshot emission also failed:', e);
            }
        } finally {
            this.isProcessingScreenshot = false;
    
            if (this.screenshotQueue.length > 0) {
                const nextScreenshot = this.screenshotQueue.shift();
                if (nextScreenshot) {
                    setTimeout(() => this.emitScreenshot(nextScreenshot), 1000 / SCREENCAST_CONFIG.targetFPS);
                }
            }
        }
    };

}