import { NextResponse } from 'next/server';
import { getServerSession } from 'next-auth';
import { authOptions } from "@/app/api/auth/options";
import { getEmails } from '@/lib/services/email-service';
import { 
  getCachedEmailList, 
  cacheEmailList, 
  invalidateFolderCache 
} from '@/lib/redis';
import { PrismaClient } from '@prisma/client';
import { logger } from '@/lib/logger';

const prisma = new PrismaClient();

// Simple in-memory cache (will be removed in a future update)
interface EmailCacheEntry {
  data: any;
  timestamp: number;
}

// Cache for 1 minute only
const CACHE_TTL = 60 * 1000;
const emailListCache: Record<string, EmailCacheEntry> = {};

export async function GET(request: Request) {
  // Authenticate user (declare outside try to access in catch)
    const session = await getServerSession(authOptions);
    if (!session || !session.user?.id) {
      return NextResponse.json(
        { error: "Not authenticated" },
        { status: 401 }
      );
    }

  try {

    // Extract query parameters
    const { searchParams } = new URL(request.url);
    const page = parseInt(searchParams.get("page") || "1");
    const perPage = parseInt(searchParams.get("perPage") || "20");
    const folder = searchParams.get("folder") || "INBOX";
    const searchQuery = searchParams.get("search") || "";
    const accountId = searchParams.get("accountId") || "";
    const checkOnly = searchParams.get("checkOnly") === "true";
    const refresh = searchParams.get("refresh") === "true";
    
    // CRITICAL FIX: Log exact parameters received by the API
    logger.debug('[COURRIER_API] Received request', {
      folder,
      accountIdHash: accountId ? Buffer.from(accountId).toString('base64').slice(0, 12) : null,
      page,
      checkOnly,
      refresh,
      userIdHash: Buffer.from(session.user.id).toString('base64').slice(0, 12),
    });
    
    // CRITICAL FIX: More robust parameter normalization
    // 1. If folder contains an account prefix, extract it but DO NOT use it
    // 2. Always prioritize the explicit accountId parameter
    let normalizedFolder = folder;
    let effectiveAccountId = accountId || 'default';
    
    if (folder.includes(':')) {
      const parts = folder.split(':');
      const folderAccountId = parts[0];
      normalizedFolder = parts[1];
      
      logger.debug('[COURRIER_API] Folder has prefix, normalized', {
        folderAccountId,
        normalizedFolder
      });
      // We intentionally DO NOT use folderAccountId here - the explicit accountId parameter takes precedence
    }
    
    // CRITICAL FIX: Enhanced logging for parameter resolution
    logger.debug('[COURRIER_API] Using normalized parameters', {
      folder: normalizedFolder,
      accountIdHash: Buffer.from(effectiveAccountId).toString('base64').slice(0, 12),
      userIdHash: Buffer.from(session.user.id).toString('base64').slice(0, 12),
    });
    
    // If refresh=true, invalidate cache before fetching
    if (refresh) {
      logger.debug('[COURRIER_API] Refresh requested - invalidating cache', {
        userIdHash: Buffer.from(session.user.id).toString('base64').slice(0, 12),
        accountIdHash: Buffer.from(effectiveAccountId).toString('base64').slice(0, 12),
        folder: normalizedFolder
      });
      await invalidateFolderCache(session.user.id, effectiveAccountId, normalizedFolder);
    }
    
    // Try to get from Redis cache first, but only if it's not a search query, not checkOnly, and not refresh
    if (!searchQuery && !checkOnly && !refresh) {
      // CRITICAL FIX: Use consistent cache key format with the correct account ID
      logger.debug('[COURRIER_API] Checking Redis cache', {
        userIdHash: Buffer.from(session.user.id).toString('base64').slice(0, 12),
        accountIdHash: Buffer.from(effectiveAccountId).toString('base64').slice(0, 12),
        folder: normalizedFolder,
        page,
        perPage
      });
      const cachedEmails = await getCachedEmailList(
        session.user.id,
        effectiveAccountId,  // Use effective account ID for consistent cache key
        normalizedFolder,    // Use normalized folder name without prefix
        page,
        perPage
      );
      if (cachedEmails) {
        logger.debug('[COURRIER_API] Using Redis cached emails', {
          userIdHash: Buffer.from(session.user.id).toString('base64').slice(0, 12),
          accountIdHash: Buffer.from(effectiveAccountId).toString('base64').slice(0, 12),
          folder: normalizedFolder,
          page,
          perPage
        });
        return NextResponse.json(cachedEmails);
      }
    }

    logger.debug('[COURRIER_API] Redis cache miss, fetching from IMAP', {
      userIdHash: Buffer.from(session.user.id).toString('base64').slice(0, 12),
      accountIdHash: Buffer.from(effectiveAccountId).toString('base64').slice(0, 12),
      folder: normalizedFolder,
      page,
      perPage
    });

    // Use the email service to fetch emails with the normalized folder and effective account ID
    // CRITICAL FIX: Pass parameters in the correct order and with proper values
    const emailsResult = await getEmails(
      session.user.id,      // userId
      normalizedFolder,     // folder (without prefix)
      page,                 // page
      perPage,              // perPage
      effectiveAccountId,   // accountId
      checkOnly             // checkOnly flag - only check for new emails without loading full content
    );

    // CRITICAL FIX: Log when emails are returned from IMAP
    logger.debug('[COURRIER_API] Successfully fetched emails from IMAP', {
      count: emailsResult.emails.length,
      accountIdHash: Buffer.from(effectiveAccountId).toString('base64').slice(0, 12),
      userIdHash: Buffer.from(session.user.id).toString('base64').slice(0, 12),
    });

    // The result is already cached in the getEmails function (if not checkOnly)
    return NextResponse.json(emailsResult);
  } catch (error: any) {
    logger.error('[COURRIER_API] Error fetching emails', {
      error: error instanceof Error ? error.message : String(error),
      userIdHash: session?.user?.id ? Buffer.from(session.user.id).toString('base64').slice(0, 12) : null,
    });
    return NextResponse.json(
      { error: "Failed to fetch emails", message: error.message },
      { status: 500 }
    );
  }
}

export async function POST(request: Request) {
  try {
    const session = await getServerSession(authOptions);
    if (!session?.user?.id) {
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
    }
    
    const { emailId, folderName, accountId } = await request.json();
    
    if (!emailId) {
      return NextResponse.json({ error: 'Missing emailId parameter' }, { status: 400 });
    }
    
    // Use account ID or default if not provided
    const effectiveAccountId = accountId || 'default';
    
    // Normalize folder name by removing account prefix if present
    const normalizedFolder = folderName && folderName.includes(':') 
      ? folderName.split(':')[1] 
      : folderName;
    
    // Log the cache invalidation operation
    logger.debug('[COURRIER_API] Invalidating cache', {
      userIdHash: Buffer.from(session.user.id).toString('base64').slice(0, 12),
      accountIdHash: Buffer.from(effectiveAccountId).toString('base64').slice(0, 12),
      folder: normalizedFolder || 'all folders'
    });
    
    // Invalidate Redis cache for the folder
    if (normalizedFolder) {
      await invalidateFolderCache(session.user.id, effectiveAccountId, normalizedFolder);
    } else {
      // If no folder specified, invalidate all folders (using a wildcard pattern)
      const folders = ['INBOX', 'Sent', 'Drafts', 'Trash', 'Junk'];
      for (const folder of folders) {
        await invalidateFolderCache(session.user.id, effectiveAccountId, folder);
      }
    }
    
    return NextResponse.json({ success: true });
  } catch (error) {
    logger.error('[COURRIER_API] Error in POST handler', {
      error: error instanceof Error ? error.message : String(error)
    });
    return NextResponse.json({ error: 'An unexpected error occurred' }, { status: 500 });
  }
}