import { NextResponse } from 'next/server';
import { getServerSession } from 'next-auth';
import { authOptions } from '@/lib/auth';
import { getMailboxes } from '@/lib/services/email-service';
import { getRedisClient } from '@/lib/redis';
import { getImapConnection } from '@/lib/services/email-service';
import { MailCredentials } from '@prisma/client';
import { prisma } from '@/lib/prisma';

// Keep track of last prefetch time for each user
const lastPrefetchMap = new Map<string, number>();
const PREFETCH_COOLDOWN_MS = 30000; // 30 seconds cooldown between prefetches

// Cache TTL for folders in Redis (5 minutes)
const FOLDERS_CACHE_TTL = 3600; // 1 hour

// Redis key for folders cache
const FOLDERS_CACHE_KEY = (userId: string, accountId: string) => `email:folders:${userId}:${accountId}`;

/**
 * This endpoint is called when the app initializes to check if the user has email credentials
 * and to start prefetching email data in the background if they do
 */
export async function GET() {
  try {
    const session = await getServerSession(authOptions);
    if (!session?.user?.id) {
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
    }

    // Get Redis connection
    const redis = getRedisClient();
    if (!redis) {
      return NextResponse.json({ error: 'Redis connection failed' }, { status: 500 });
    }

    // Get user with their accounts
    const user = await prisma.user.findUnique({
      where: { id: session.user.id },
      include: { mailCredentials: true }
    });

    if (!user) {
      return NextResponse.json({ error: 'User not found' }, { status: 404 });
    }

    // Get all accounts for the user
    const accounts = (user.mailCredentials || []) as MailCredentials[];
    if (accounts.length === 0) {
      return NextResponse.json({ error: 'No email accounts found' }, { status: 404 });
    }

    // Fetch folders for each account
    const accountsWithFolders = await Promise.all(
      accounts.map(async (account: MailCredentials) => {
        const cacheKey = FOLDERS_CACHE_KEY(user.id, account.id);
        // Try to get folders from Redis cache first
        const cachedFolders = await redis.get(cacheKey);
        if (cachedFolders) {
          return {
            ...account,
            folders: JSON.parse(cachedFolders)
          };
        }

        // If not in cache, fetch from IMAP
        const client = await getImapConnection(user.id, account.id);
        if (!client) {
          return {
            ...account,
            folders: ['INBOX', 'Sent', 'Drafts', 'Trash', 'Junk']
          };
        }

        try {
          const folders = await getMailboxes(client);
          // Cache the folders in Redis
          await redis.set(
            cacheKey,
            JSON.stringify(folders),
            'EX',
            FOLDERS_CACHE_TTL
          );
          return {
            ...account,
            folders
          };
        } catch (error) {
          console.error(`Error fetching folders for account ${account.id}:`, error);
          return {
            ...account,
            folders: ['INBOX', 'Sent', 'Drafts', 'Trash', 'Junk']
          };
        }
      })
    );

    return NextResponse.json({
      accounts: accountsWithFolders
    });
  } catch (error) {
    console.error('Error in session route:', error);
    return NextResponse.json(
      { error: 'Internal server error' },
      { status: 500 }
    );
  }
}