import { logger } from '../logger';
import fs from 'fs/promises';
import path from 'path';
import cron from 'node-cron';
import { redis } from '../lib/redis';

const TEMP_DIR = '/tmp';
const GLOBAL_MAX_AGE = 30 * 60 * 1000; // 30 minutes
const PER_TENANT_QUOTA_MB = 100; // 100MB per tenant limit
const CLEANUP_LOCK_KEY = 'lock:cleanup:temp_files';
const LOCK_TTL = 1800; // 30 minutes in seconds

/**
 * Cleanup Service
 * 
 * Manages /tmp storage by enforcing age limits and per-tenant quotas.
 * Uses a Redis lock to ensure only one instance runs maintenance at a time.
 */
export async function cleanTempFiles() {
    // 0. Acquire distributed lock
    const lock = await redis.set(CLEANUP_LOCK_KEY, 'locked', 'EX', LOCK_TTL, 'NX');
    if (!lock) {
        logger.info('[CLEANUP] Maintenance already in progress on another instance. Skipping.');
        return;
    }

    const now = Date.now();

    try {
        const folders = ['', 'audio', 'images', 'documents'];
        const tenantUsage: Record<string, number> = {};
        const tenantFiles: Record<string, { path: string, size: number, mtime: number }[]> = {};
        
        for (const folder of folders) {
            const dirPath = path.join(TEMP_DIR, folder);
            
            try {
                await fs.access(dirPath);
            } catch {
                continue; 
            }

            const files = await fs.readdir(dirPath);
            
            for (const file of files) {
                const filePath = path.join(dirPath, file);
                const stats = await fs.stat(filePath);
                
                if (stats.isDirectory()) continue;

                // 1. Check Age (Global cleanup)
                const age = now - stats.mtimeMs;
                if (age > GLOBAL_MAX_AGE) {
                    await fs.unlink(filePath);
                    logger.info(`[CLEANUP] Deleted old file (Age): ${filePath}`);
                    continue;
                }

                // 2. Track usage by tenant (Assumes files are named orgId_filename)
                const orgId = file.split('_')[0];
                if (orgId && orgId.length > 10) { // Basic orgId check
                    tenantUsage[orgId] = (tenantUsage[orgId] || 0) + stats.size;
                    if (!tenantFiles[orgId]) tenantFiles[orgId] = [];
                    tenantFiles[orgId].push({ path: filePath, size: stats.size, mtime: stats.mtimeMs });
                }
            }
        }

        // 3. Enforce Quotas
        for (const orgId in tenantUsage) {
            const usageMB = tenantUsage[orgId] / (1024 * 1024);
            if (usageMB > PER_TENANT_QUOTA_MB) {
                logger.warn(`[CLEANUP] Quota exceeded for Org ${orgId}: ${usageMB.toFixed(2)}MB. Cleaning oldest files...`);
                
                // Sort by mtime (oldest first)
                const files = tenantFiles[orgId].sort((a, b) => a.mtime - b.mtime);
                let freed = 0;
                const targetToFree = (usageMB - (PER_TENANT_QUOTA_MB * 0.8)) * 1024 * 1024; // Free up to 80% of quota

                for (const file of files) {
                    await fs.unlink(file.path);
                    freed += file.size;
                    if (freed >= targetToFree) break;
                }
                logger.info(`[CLEANUP] Freed ${(freed / (1024 * 1024)).toFixed(2)}MB for Org ${orgId}`);
            }
        }

    } catch (err: any) {
        logger.error({ err }, '[CLEANUP] Error during maintenance');
    } finally {
        // 4. Release lock
        await redis.del(CLEANUP_LOCK_KEY);
    }
}

/**
 * Starts a cron job that runs every 30 minutes.
 */
export function startCleanupCron() {
    cron.schedule('*/30 * * * *', async () => {
        logger.info('[CLEANUP] 🧹 Starting scheduled maintenance...');
        await cleanTempFiles();
    });
    
    // Also run once at startup
    cleanTempFiles();
}