// Request queue and throttling manager
export interface QueuedRequest {
    id: string;
    type: 'transcribe' | 'translate' | 'tts';
    request: () => Promise<any>;
    resolve: (value: any) => void;
    reject: (reason?: any) => void;
    retryCount: number;
    priority: number;
    timestamp: number;
}

export class RequestQueueManager {
    private static instance: RequestQueueManager;
    private queue: QueuedRequest[] = [];
    private activeRequests: Map<string, QueuedRequest> = new Map();
    private maxConcurrent = 2; // Maximum concurrent requests
    private maxRetries = 3;
    private retryDelay = 1000; // Base retry delay in ms
    private isProcessing = false;

    // Rate limiting
    private requestHistory: number[] = [];
    private maxRequestsPerMinute = 30;
    private maxRequestsPerSecond = 2;

    private constructor() {
        // Start processing queue
        this.startProcessing();
    }

    static getInstance(): RequestQueueManager {
        if (!RequestQueueManager.instance) {
            RequestQueueManager.instance = new RequestQueueManager();
        }
        return RequestQueueManager.instance;
    }

    // Add request to queue
    async enqueue<T>(
        type: 'transcribe' | 'translate' | 'tts',
        request: () => Promise<T>,
        priority: number = 5
    ): Promise<T> {
        // Check rate limits
        if (!this.checkRateLimits()) {
            throw new Error('Rate limit exceeded. Please slow down.');
        }

        return new Promise((resolve, reject) => {
            const id = this.generateId();
            const queuedRequest: QueuedRequest = {
                id,
                type,
                request,
                resolve,
                reject,
                retryCount: 0,
                priority,
                timestamp: Date.now()
            };

            // Add to queue based on priority
            this.addToQueue(queuedRequest);
            
            // Log queue status
            console.log(`Request queued: ${type}, Queue size: ${this.queue.length}, Active: ${this.activeRequests.size}`);
        });
    }

    private addToQueue(request: QueuedRequest): void {
        // Insert based on priority (higher priority first)
        const insertIndex = this.queue.findIndex(item => item.priority < request.priority);
        if (insertIndex === -1) {
            this.queue.push(request);
        } else {
            this.queue.splice(insertIndex, 0, request);
        }
    }

    private checkRateLimits(): boolean {
        const now = Date.now();
        
        // Clean old entries
        this.requestHistory = this.requestHistory.filter(
            time => now - time < 60000 // Keep last minute
        );

        // Check per-second limit
        const lastSecond = this.requestHistory.filter(
            time => now - time < 1000
        ).length;
        
        if (lastSecond >= this.maxRequestsPerSecond) {
            console.warn('Per-second rate limit reached');
            return false;
        }

        // Check per-minute limit
        if (this.requestHistory.length >= this.maxRequestsPerMinute) {
            console.warn('Per-minute rate limit reached');
            return false;
        }

        // Record this request
        this.requestHistory.push(now);
        return true;
    }

    private async startProcessing(): Promise<void> {
        if (this.isProcessing) return;
        this.isProcessing = true;

        while (true) {
            await this.processQueue();
            await this.delay(100); // Check queue every 100ms
        }
    }

    private async processQueue(): Promise<void> {
        // Check if we can process more requests
        if (this.activeRequests.size >= this.maxConcurrent || this.queue.length === 0) {
            return;
        }

        // Get next request
        const request = this.queue.shift();
        if (!request) return;

        // Mark as active
        this.activeRequests.set(request.id, request);

        try {
            // Execute request
            const result = await request.request();
            request.resolve(result);
            console.log(`Request completed: ${request.type}`);
        } catch (error) {
            console.error(`Request failed: ${request.type}`, error);
            
            // Check if we should retry
            if (request.retryCount < this.maxRetries && this.shouldRetry(error)) {
                request.retryCount++;
                const delay = this.calculateRetryDelay(request.retryCount);
                console.log(`Retrying request ${request.type} in ${delay}ms (attempt ${request.retryCount})`);
                
                // Re-queue with delay
                setTimeout(() => {
                    this.addToQueue(request);
                }, delay);
            } else {
                // Max retries reached or non-retryable error
                request.reject(error);
            }
        } finally {
            // Remove from active
            this.activeRequests.delete(request.id);
        }
    }

    private shouldRetry(error: any): boolean {
        // Retry on network errors or 5xx status codes
        if (error.message?.includes('network') || error.message?.includes('Network')) {
            return true;
        }
        
        if (error.status >= 500 && error.status < 600) {
            return true;
        }
        
        // Don't retry on client errors (4xx)
        if (error.status >= 400 && error.status < 500) {
            return false;
        }
        
        return true;
    }

    private calculateRetryDelay(retryCount: number): number {
        // Exponential backoff with jitter
        const baseDelay = this.retryDelay * Math.pow(2, retryCount - 1);
        const jitter = Math.random() * 0.3 * baseDelay; // 30% jitter
        return Math.min(baseDelay + jitter, 30000); // Max 30 seconds
    }

    private generateId(): string {
        return `${Date.now()}-${Math.random().toString(36).substr(2, 9)}`;
    }

    private delay(ms: number): Promise<void> {
        return new Promise(resolve => setTimeout(resolve, ms));
    }

    // Get queue status
    getStatus(): {
        queueLength: number;
        activeRequests: number;
        requestsPerMinute: number;
    } {
        const now = Date.now();
        const recentRequests = this.requestHistory.filter(
            time => now - time < 60000
        ).length;

        return {
            queueLength: this.queue.length,
            activeRequests: this.activeRequests.size,
            requestsPerMinute: recentRequests
        };
    }

    // Clear queue (for emergency use)
    clearQueue(): void {
        this.queue.forEach(request => {
            request.reject(new Error('Queue cleared'));
        });
        this.queue = [];
    }

    // Update settings
    updateSettings(settings: {
        maxConcurrent?: number;
        maxRequestsPerMinute?: number;
        maxRequestsPerSecond?: number;
    }): void {
        if (settings.maxConcurrent !== undefined) {
            this.maxConcurrent = settings.maxConcurrent;
        }
        if (settings.maxRequestsPerMinute !== undefined) {
            this.maxRequestsPerMinute = settings.maxRequestsPerMinute;
        }
        if (settings.maxRequestsPerSecond !== undefined) {
            this.maxRequestsPerSecond = settings.maxRequestsPerSecond;
        }
    }
}