import { put } from '@vercel/blob';
import { sql } from '@vercel/postgres';
import { getUserFromRequest } from '../../../../lib/permission-middleware';
import { checkGenerateRateLimit } from '../../../../lib/rate-limit.js';

export default async function handler(req, res) {
  if (req.method !== 'POST') {
    return res.status(405).json({ error: 'Method not allowed' });
  }

  try {
    // Get authenticated user
    const user = await getUserFromRequest(req);
    if (!user) {
      return res.status(401).json({ error: 'Authentication required' });
    }

    const { allowed, reset } = await checkGenerateRateLimit(req, user.userId);
    if (!allowed) {
      res.setHeader('Retry-After', Math.ceil((reset - Date.now()) / 1000));
      return res.status(429).json({ error: 'Too many attempts. Try again later.' });
    }

    // Get user information for avatar generation
    const userResult = await sql`
      SELECT email, first_name, last_name, username FROM users WHERE id = ${user.userId}
    `;

    if (userResult.rows.length === 0) {
      return res.status(404).json({ error: 'User not found' });
    }

    const userData = userResult.rows[0];

    try {
      // Delete old avatar if exists
      await deleteOldAvatar(user.userId);

      // Generate avatar using a service (we'll use DiceBear Avatars as an example)
      const avatarStyle = 'initials'; // You can change this to other styles like 'avataaars', 'bottts', etc.
      const seed = userData.username || userData.email || `user-${user.userId}`;
      const initials = getInitials(userData);
      
      // Create avatar URL with DiceBear API
      const avatarUrl = `https://api.dicebear.com/7.x/${avatarStyle}/svg?seed=${encodeURIComponent(seed)}&chars=2&backgroundColor=d84315,ff5722,ff7043&textColor=ffffff&fontSize=40`;

      // Fetch the generated avatar
      const avatarResponse = await fetch(avatarUrl);
      if (!avatarResponse.ok) {
        throw new Error('Failed to generate avatar');
      }

      const avatarBuffer = Buffer.from(await avatarResponse.arrayBuffer());
      
      // Generate unique filename
      const filename = `avatars/generated-${user.userId}-${Date.now()}.svg`;

      // Upload to Vercel Blob
      const blob = await put(filename, avatarBuffer, {
        access: 'public',
        contentType: 'image/svg+xml',
      });

      // Save avatar info to database
      await sql`
        INSERT INTO user_avatars (user_id, filename, original_name, mime_type, file_size, file_path, is_active)
        VALUES (${user.userId}, ${filename}, 'generated-avatar.svg', 'image/svg+xml', ${avatarBuffer.length}, ${blob.url}, true)
      `;

      // Update user's avatar_url
      await sql`
        UPDATE users 
        SET avatar_url = ${blob.url}, updated_at = CURRENT_TIMESTAMP
        WHERE id = ${user.userId}
      `;

      res.status(200).json({
        message: 'Avatar generated successfully',
        avatar_url: blob.url
      });

    } catch (generateError) {
      console.error('Avatar generation error:', generateError);
      res.status(500).json({ error: 'Failed to generate avatar' });
    }

  } catch (error) {
    console.error('Avatar generation API error:', error);
    res.status(500).json({ error: 'Internal server error' });
  }
}

/**
 * Get user initials for avatar generation
 */
function getInitials(userData) {
  if (userData.first_name || userData.last_name) {
    return `${userData.first_name?.charAt(0) || ''}${userData.last_name?.charAt(0) || ''}`.toUpperCase();
  }
  if (userData.username) {
    return userData.username.substring(0, 2).toUpperCase();
  }
  return userData.email?.charAt(0).toUpperCase() || 'U';
}

/**
 * Delete old avatar from Vercel Blob and database
 */
async function deleteOldAvatar(userId) {
  try {
    // Get current active avatar
    const avatarResult = await sql`
      SELECT file_path, filename FROM user_avatars 
      WHERE user_id = ${userId} AND is_active = true
    `;

    if (avatarResult.rows.length > 0) {
      const avatar = avatarResult.rows[0];
      
      // Delete from Vercel Blob
      try {
        const { del } = await import('@vercel/blob');
        await del(avatar.file_path);
      } catch (blobError) {
        console.warn('Failed to delete blob file:', blobError);
        // Continue anyway - the database record should still be cleaned up
      }

      // Mark as inactive in database
      await sql`
        UPDATE user_avatars 
        SET is_active = false, updated_at = CURRENT_TIMESTAMP
        WHERE user_id = ${userId} AND is_active = true
      `;
    }
  } catch (error) {
    console.error('Error deleting old avatar:', error);
    // Don't throw - this shouldn't prevent new uploads
  }
} 