import { EventEmitter } from 'events';
import { randomUUID } from 'crypto';

export default class BrowserPool extends EventEmitter {
    constructor(options = {}) {
        super();
        this.chromium = options.chromium;
        if (!this.chromium) throw new Error('Chromium instance must be provided');

        this.maxSize = options.maxSize || 5;
        this.minSize = options.minSize || 1;
        this.maxUsage = options.maxUsage || 100;
        this.maxIdleTime = options.maxIdleTime || 300000;
        this.createTimeout = options.createTimeout || 30000;
        this.validateInterval = options.validateInterval || 60000;
        this.getTimeout = options.getTimeout || 30000;

        this.availableInstances = [];
        this.busyInstances = new Set();
        this.totalInstances = 0;
        this.waitingQueue = [];
        this.stats = { created: 0, destroyed: 0, borrowed: 0, returned: 0, timeouts: 0, errors: 0 };
        
        this.isShuttingDown = false;
        this.healthCheckInterval = null;
    }

    async initialize() {
        console.log(`[BrowserPool] Initializing pool with min: ${this.minSize}, max: ${this.maxSize}`);
        const createPromises = Array.from({ length: this.minSize }, () => this.createInstance());
        try {
            await Promise.all(createPromises);
            console.log(`[BrowserPool] Pool initialized with ${this.availableInstances.length} instances.`);
        } catch (error) {
            console.error('[BrowserPool] Failed to initialize pool:', error.message);
            await this.shutdown();
            throw error;
        }
        this.startHealthCheck();
    }

    async createInstance() {
        if (this.isShuttingDown) { throw new Error('Pool is shutting down'); }
        if (this.totalInstances >= this.maxSize) { return null; }

        const startTime = Date.now();
        let browser = null;
        this.totalInstances++;
        try {
            console.log('[BrowserPool] Creating new browser instance...');
            browser = await Promise.race([
                this.chromium.launch({
                    headless: true,
                    args: [
                        // '--no-sandbox', '--disable-setuid-sandbox', '--disable-blink-features=AutomationControlled',
                        // '--disable-web-security', '--autoplay-policy=no-user-gesture-required',
                        // '--disable-dev-shm-usage', '--disable-gpu', '--single-process', '--no-zygote',
                        // '--disable-infobars', '--disable-notifications', '--disable-extensions',
                       '--no-sandbox',
                        '--disable-setuid-sandbox',
                        '--disable-blink-features=AutomationControlled',
                        '--disable-web-security',
                        '--autoplay-policy=no-user-gesture-required',
                        '--disable-dev-shm-usage',      // 避免共享内存问题
                        '--disable-gpu',                // 减少资源使用
                        '--no-first-run',              // 跳过首次运行设置
                        '--disable-default-apps'        // 禁用默认应用
                    ]
                }),
                new Promise((_, reject) => setTimeout(() => reject(new Error('Browser creation timeout')), this.createTimeout))
            ]);

            const instance = {
                browser, id: `browser_${randomUUID().slice(0, 8)}`, createdAt: Date.now(),
                lastUsed: Date.now(), usageCount: 0, isHealthy: true
            };

            browser.on('disconnected', () => {
                console.log(`[BrowserPool] Browser ${instance.id} disconnected unexpectedly.`);
                this.destroyInstance(instance, true);
            });

            this.stats.created++;
            console.log(`[BrowserPool] Browser instance created: ${instance.id} (${Date.now() - startTime}ms)`);
            this.emit('instanceCreated', instance);
            this.availableInstances.push(instance);
            this.processWaitingQueue();
            return instance;
        } catch (error) {
            this.totalInstances--;
            this.stats.errors++;
            console.error('[BrowserPool] Failed to create browser instance:', error.message);
            if (browser) await browser.close().catch(e => console.error(`Error closing failed browser: ${e.message}`));
            throw error;
        }
    }

    get() {
        if (this.isShuttingDown) return Promise.reject(new Error('Pool is shutting down'));
        return new Promise((resolve, reject) => {
            const timeoutId = setTimeout(() => {
                this.waitingQueue = this.waitingQueue.filter(w => w.resolve !== resolve);
                this.stats.timeouts++;
                reject(new Error(`Browser acquisition timeout after ${this.getTimeout}ms`));
            }, this.getTimeout);

            const tryAcquire = async () => {
                while (this.availableInstances.length > 0) {
                    const instance = this.availableInstances.shift();
                    if (await this.validateInstance(instance)) {
                        this.busyInstances.add(instance);
                        instance.lastUsed = Date.now();
                        instance.usageCount++;
                        this.stats.borrowed++;
                        clearTimeout(timeoutId);
                        return resolve(instance);
                    } else {
                        await this.destroyInstance(instance);
                    }
                }
                if (this.totalInstances < this.maxSize) {
                    this.createInstance().catch(err => console.error(`[BrowserPool] Background instance creation failed: ${err.message}`));
                }
                
                this.waitingQueue.push({ resolve, reject, timeoutId });
                console.log(`[BrowserPool] No available instances, request added to waiting queue (size: ${this.waitingQueue.length})`);
            };
            
            tryAcquire();
        });
    }

    async release(instance) {
        if (!instance || !this.busyInstances.has(instance)) { return; }
        this.busyInstances.delete(instance);
        this.stats.returned++;
        if (this.isShuttingDown || !await this.validateInstance(instance) || instance.usageCount >= this.maxUsage) {
            await this.destroyInstance(instance);
        } else {
            try {
                const contexts = instance.browser.contexts();
                // 默认上下文是第一个，我们不关闭它，只关闭后续创建的
                for (let i = 1; i < contexts.length; i++) {
                    await contexts[i].close();
                }
                this.availableInstances.push(instance);
            } catch (e) {
                console.warn(`[BrowserPool] Error cleaning up contexts for ${instance.id}, destroying it.`, e.message);
                await this.destroyInstance(instance);
            }
        }
        this.processWaitingQueue();
    }

    async destroyInstance(instance, isDisconnected = false) {
        if (!instance) return;
        this.busyInstances.delete(instance);
        const index = this.availableInstances.indexOf(instance);
        if (index > -1) this.availableInstances.splice(index, 1);
        if (!isDisconnected && instance.browser && instance.browser.isConnected()) {
            await instance.browser.close().catch(e => console.error(`[BrowserPool] Error closing browser on destroy: ${e.message}`));
        }
        if (this.totalInstances > 0) this.totalInstances--;
        this.stats.destroyed++;
        console.log(`[BrowserPool] Instance ${instance.id} destroyed.`);
        this.emit('instanceDestroyed', instance);
        if (!this.isShuttingDown && this.totalInstances < this.minSize) {
            this.createInstance().catch(err => console.error(`[BrowserPool] Failed to replenish instance: ${err.message}`));
        }
    }
    
    processWaitingQueue() {
        if (this.waitingQueue.length > 0 && this.availableInstances.length > 0) {
            console.log('[BrowserPool] Processing waiting queue...');
            const waiter = this.waitingQueue.shift();
            const instance = this.availableInstances.shift();
            this.busyInstances.add(instance);
            instance.lastUsed = Date.now();
            instance.usageCount++;
            this.stats.borrowed++;
            clearTimeout(waiter.timeoutId);
            waiter.resolve(instance);
        }
    }

    async validateInstance(instance) {
        if (!instance || !instance.browser || !instance.browser.isConnected()) return false;
        try {
            // 一个更轻量级的检查，创建一个新的 incognito context
            const context = await instance.browser.newContext();
            await context.close();
            return true;
        } catch (error) {
            console.warn(`[BrowserPool] Instance ${instance.id} validation failed.`);
            return false;
        }
    }

    startHealthCheck() {
        this.healthCheckInterval = setInterval(() => this.performHealthCheck(), this.validateInterval);
    }

    async performHealthCheck() {
        if (this.isShuttingDown) return;
        const now = Date.now();
        const idleInstances = this.availableInstances.slice(); // 创建副本以安全遍历
        for (const instance of idleInstances) {
            if (this.totalInstances > this.minSize && now - instance.lastUsed > this.maxIdleTime) {
                console.log(`[BrowserPool] Removing idle instance ${instance.id}`);
                await this.destroyInstance(instance);
            }
        }
    }

    getStats() {
        return {
            ...this.stats,
            pool: {
                available: this.availableInstances.length,
                busy: this.busyInstances.size,
                total: this.totalInstances,
                waiting: this.waitingQueue.length
            }
        };
    }

    async shutdown() {
        console.log('[BrowserPool] Shutting down...');
        this.isShuttingDown = true;
        if (this.healthCheckInterval) clearInterval(this.healthCheckInterval);

        for (const waiter of this.waitingQueue) {
            clearTimeout(waiter.timeoutId);
            waiter.reject(new Error('Pool is shutting down'));
        }
        this.waitingQueue = [];
        
        const allInstances = [...this.availableInstances, ...Array.from(this.busyInstances)];
        await Promise.all(allInstances.map(instance => instance.browser.close()));
        console.log('[BrowserPool] All browser instances closed.');
    }
}

// 使用 module.exports 导出类
// module.exports = { BrowserPool };