// src/utils/rateLimitedQueue.ts
import { forensicConfig } from './forensicConfig.js';

import dotenv from "dotenv";

dotenv.config();

const RATE_LIMIT_DELAY_MS = forensicConfig.getThresholds().rateLimitDelayMs;

export type Task<T = unknown> = () => Promise<T>;

interface QueuedTask {
  id: string;
  task: Task;
  addedAt: number;
  status: 'queued' | 'processing' | 'completed' | 'failed';
  startedAt?: number;
  completedAt?: number;
}

export interface QueueStatus {
  queueLength: number;
  isProcessing: boolean;
  estimatedWaitTime: number;
  currentPosition?: number;
  taskStatus?: string;
}

class RateLimitedQueue {
  private tasks: QueuedTask[] = [];
  private isProcessing = false;
  private delayMs = RATE_LIMIT_DELAY_MS;
  private lastProcessedAt = 0;
  private currentlyProcessingTaskId: string | null = null;
  
  private cleanupInterval: NodeJS.Timeout;
  private readonly TASK_RETENTION_MS = 30000; 

  constructor() {
    this.cleanupInterval = setInterval(() => {
      this.cleanupOldTasks();
    }, 30000);
  }

  private cleanupOldTasks(): void {
    const now = Date.now();
    const initialLength = this.tasks.length;
    
    this.tasks = this.tasks.filter(task => {
      if (task.status === 'queued' || task.status === 'processing') {
        return true;
      }
      
      if (task.completedAt && (now - task.completedAt) > this.TASK_RETENTION_MS) {
        return false;
      }
      
      return true;
    });
    
    const cleaned = initialLength - this.tasks.length;
    if (cleaned > 0) {
      console.log(`[QUEUE] Cleaned up ${cleaned} old tasks, ${this.tasks.length} remaining`);
    }
  }

  public shutdown(): void {
    if (this.cleanupInterval) {
      clearInterval(this.cleanupInterval);
    }
  }

  add<T>(task: Task<T>, taskId?: string): Promise<T> {
    const id = taskId || this.generateTaskId();

    return new Promise<T>((resolve, reject) => {
      const queuedTask: QueuedTask = {
        id,
        task: async () => {
          try {
            const result = await task();
            resolve(result);
            return result;
          } catch (err) {
            reject(err);
            throw err;
          }
        },
        addedAt: Date.now(),
        status: 'queued'
      };
      
      this.tasks.push(queuedTask);
      
      setTimeout(() => {
        this.processQueue();
      }, 100);
    });
  }

  getStatus(taskId?: string): QueueStatus {
    const queuedTasks = this.tasks.filter(t => t.status === 'queued');
    const processingTasks = this.tasks.filter(t => t.status === 'processing');
    const queueLength = queuedTasks.length + processingTasks.length;
    
    const now = Date.now();
    
    let estimatedWaitTime = 0;
    if (queueLength > 0) {
      if (this.isProcessing && this.lastProcessedAt > 0) {
        const timeSinceLastRequest = now - this.lastProcessedAt;
        const remainingDelay = Math.max(0, this.delayMs * 2 - timeSinceLastRequest);
        estimatedWaitTime = remainingDelay + queuedTasks.length * this.delayMs;
      } else {
        estimatedWaitTime = queueLength * this.delayMs;
      }
    }

    const status: QueueStatus = {
      queueLength,
      isProcessing: this.isProcessing,
      estimatedWaitTime
    };

    if (taskId) {
      const task = this.tasks.find(t => t.id === taskId);
      
      if (task) {
        status.taskStatus = task.status;
        
        if (task.status === 'processing') {
          status.currentPosition = 1;
        } else if (task.status === 'queued') {
          const queuedTasksInOrder = this.tasks
            .filter(t => t.status === 'queued')
            .sort((a, b) => a.addedAt - b.addedAt);
          
          const positionInQueue = queuedTasksInOrder.findIndex(t => t.id === taskId);
          
          if (positionInQueue >= 0) {
            const processingOffset = processingTasks.length > 0 ? 1 : 0;
            status.currentPosition = processingOffset + positionInQueue + 1;
          }
        }
      } else {        
        const taskTimestamp = taskId.match(/ai_(\d+)_/)?.[1];
        if (taskTimestamp) {
          const taskAge = now - parseInt(taskTimestamp);
          if (taskAge < 30000) { 
            status.taskStatus = 'starting';
          } else {
            status.taskStatus = 'unknown';
          }
        }
      }
    }

    return status;
  }

  setDelay(ms: number): void {
    if (!Number.isFinite(ms) || ms < 0) return;
    this.delayMs = ms;
  }

  getDelay(): number {
    return this.delayMs;
  }

  private async processQueue(): Promise<void> {
    if (this.isProcessing) {
      return;
    }

    this.isProcessing = true;

    try {
      while (true) {
        const nextTask = this.tasks
          .filter(t => t.status === 'queued')
          .sort((a, b) => a.addedAt - b.addedAt)[0];
        
        if (!nextTask) {
          break;
        }
        
        nextTask.status = 'processing';
        nextTask.startedAt = Date.now();
        this.currentlyProcessingTaskId = nextTask.id;
        this.lastProcessedAt = Date.now();
        
        try {
          await nextTask.task();
          nextTask.status = 'completed';
          nextTask.completedAt = Date.now();
          console.log(`[QUEUE] Task ${nextTask.id} completed`);
        } catch (error) {
          nextTask.status = 'failed';
          nextTask.completedAt = Date.now();
          console.error(`[QUEUE] Task ${nextTask.id} failed:`, error);
        }
        
        this.currentlyProcessingTaskId = null;
        
        const hasMoreQueued = this.tasks.some(t => t.status === 'queued');
        if (hasMoreQueued) {
          console.log(`[QUEUE] Waiting ${this.delayMs}ms before next task`);
          await new Promise((r) => setTimeout(r, this.delayMs));
        }
      }
    } finally {
      this.isProcessing = false;
      console.log(`[QUEUE] Queue processing finished`);
    }
  }

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

const queue = new RateLimitedQueue();

export function enqueueApiCall<T>(task: Task<T>, taskId?: string): Promise<T> {
  return queue.add(task, taskId);
}

export function getQueueStatus(taskId?: string): QueueStatus {
  return queue.getStatus(taskId);
}

export function shutdownQueue(): void {
  queue.shutdown();
}

export default queue;