import { sql } from '@vercel/postgres';
import { Resend } from 'resend';

const resend = new Resend(process.env.RESEND_API_KEY);

export default async function handler(req, res) {
  // Set CORS headers
  res.setHeader('Access-Control-Allow-Origin', '*');
  res.setHeader('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
  res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization');

  // Handle preflight requests
  if (req.method === 'OPTIONS') {
    res.status(200).end();
    return;
  }

  const { id } = req.query; // collection id

  if (req.method === 'GET') {
    // Get all permissions for a collection
    try {
      const result = await sql`
        SELECT 
          cp.*,
          u.email,
          u.id as user_id,
          u.is_pending
        FROM collection_permissions cp
        JOIN users u ON cp.user_id = u.id
        WHERE cp.collection_id = ${id}
        ORDER BY cp.role, cp.created_at
      `;

      res.status(200).json(result.rows);

    } catch (error) {
      console.error('Error fetching permissions:', error);
      res.status(500).json({ error: 'Internal server error' });
    }
  } else if (req.method === 'POST') {
    // Invite user to collection
    try {
      const { email, role = 'viewer', message = '' } = req.body;

      if (!email || !['owner', 'editor', 'viewer'].includes(role)) {
        return res.status(400).json({ error: 'Valid email and role are required' });
      }

      // Check if user exists
      const userResult = await sql`
        SELECT id, email FROM users WHERE email = ${email}
      `;

      let userId;
      if (userResult.rows.length === 0) {
        // Create pending user record
        const newUserResult = await sql`
          INSERT INTO users (email, password, role, is_pending)
          VALUES (${email}, '', 'user', true)
          RETURNING id
        `;
        userId = newUserResult.rows[0].id;
      } else {
        userId = userResult.rows[0].id;
      }

      // Check if permission already exists
      const existingPermission = await sql`
        SELECT * FROM collection_permissions 
        WHERE collection_id = ${id} AND user_id = ${userId}
      `;

      if (existingPermission.rows.length > 0) {
        return res.status(409).json({ error: 'User already has access to this collection' });
      }

      // Get collection details for email
      const collectionResult = await sql`
        SELECT c.name, u.email as owner_email
        FROM collections c
        JOIN users u ON c.user_id = u.id
        WHERE c.id = ${id}
      `;

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

      const collection = collectionResult.rows[0];

      // Create permission record
      const permissionResult = await sql`
        INSERT INTO collection_permissions (collection_id, user_id, role, status, invited_by)
        VALUES (${id}, ${userId}, ${role}, 'pending', 1)
        RETURNING *
      `;

      // Generate invitation token
      const inviteToken = Buffer.from(`${id}:${userId}:${Date.now()}`).toString('base64');
      
      await sql`
        UPDATE collection_permissions 
        SET invite_token = ${inviteToken}
        WHERE id = ${permissionResult.rows[0].id}
      `;

      // Send invitation email
      const acceptUrl = `${process.env.NEXT_PUBLIC_BASE_URL || 'http://localhost:3000'}/invite/accept?token=${inviteToken}`;
      const declineUrl = `${process.env.NEXT_PUBLIC_BASE_URL || 'http://localhost:3000'}/invite/decline?token=${inviteToken}`;

      try {
        await resend.emails.send({
          from: 'TCG Vault <noreply@tcgvault.com>',
          to: email,
          subject: `You've been invited to collaborate on "${collection.name}"`,
          html: `
            <div style="font-family: Arial, sans-serif; max-width: 600px; margin: 0 auto;">
              <div style="background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); padding: 30px; text-align: center; color: white;">
                <h1 style="margin: 0; font-size: 28px;">🃏 TCG Vault</h1>
                <p style="margin: 10px 0 0 0; opacity: 0.9;">Collection Collaboration Invite</p>
              </div>
              
              <div style="padding: 30px; background: #f8f9fa;">
                <h2 style="color: #333; margin-top: 0;">You've been invited to collaborate!</h2>
                
                <p style="color: #666; line-height: 1.6;">
                  <strong>${collection.owner_email}</strong> has invited you to collaborate on the collection 
                  <strong>"${collection.name}"</strong> with <strong>${role}</strong> permissions.
                </p>
                
                ${message ? `
                  <div style="background: #e3f2fd; padding: 15px; border-left: 4px solid #2196f3; margin: 20px 0;">
                    <p style="margin: 0; color: #1976d2;"><strong>Personal message:</strong></p>
                    <p style="margin: 5px 0 0 0; color: #333;">"${message}"</p>
                  </div>
                ` : ''}
                
                <div style="margin: 30px 0;">
                  <h3 style="color: #333;">What you can do as a ${role}:</h3>
                  <ul style="color: #666; line-height: 1.8;">
                    ${role === 'owner' ? `
                      <li>Full control over the collection</li>
                      <li>Add and remove cards</li>
                      <li>Edit collection details</li>
                      <li>Manage permissions and invite others</li>
                      <li>Delete the collection</li>
                    ` : role === 'editor' ? `
                      <li>Add and remove cards</li>
                      <li>Edit collection details</li>
                      <li>View all collection content</li>
                    ` : `
                      <li>View all collection content</li>
                      <li>Browse and search cards</li>
                      <li>Export collection data</li>
                    `}
                  </ul>
                </div>
                
                <div style="text-align: center; margin: 30px 0;">
                  <a href="${acceptUrl}" style="background: #4caf50; color: white; padding: 12px 30px; text-decoration: none; border-radius: 6px; font-weight: bold; margin-right: 10px; display: inline-block;">
                    Accept Invitation
                  </a>
                  <a href="${declineUrl}" style="background: #f44336; color: white; padding: 12px 30px; text-decoration: none; border-radius: 6px; font-weight: bold; display: inline-block;">
                    Decline
                  </a>
                </div>
                
                <div style="border-top: 1px solid #ddd; padding-top: 20px; margin-top: 30px; color: #999; font-size: 14px;">
                  <p>This invitation will expire in 7 days. If you have any questions, please contact ${collection.owner_email}.</p>
                  <p>If you didn't expect this invitation, you can safely ignore this email.</p>
                </div>
              </div>
            </div>
          `
        });
      } catch (emailError) {
        console.error('Email sending failed:', emailError);
        // Continue anyway - the invitation is still created
      }

      // Log activity
      await sql`
        INSERT INTO collection_activity (collection_id, user_id, action, details)
        VALUES (${id}, 1, 'user_invited', ${JSON.stringify({ email, role, inviteToken })})
      `;

      res.status(201).json({
        message: 'Invitation sent successfully',
        permission: {
          ...permissionResult.rows[0],
          email,
          invite_token: inviteToken
        }
      });

    } catch (error) {
      console.error('Error inviting user:', error);
      res.status(500).json({ error: 'Internal server error' });
    }
  } else if (req.method === 'PUT') {
    // Update user permission
    try {
      const { userId, role, status } = req.body;

      if (!userId || !['owner', 'editor', 'viewer'].includes(role)) {
        return res.status(400).json({ error: 'Valid user ID and role are required' });
      }

      const result = await sql`
        UPDATE collection_permissions 
        SET role = ${role}, status = ${status || 'active'}, updated_at = NOW()
        WHERE collection_id = ${id} AND user_id = ${userId}
        RETURNING *
      `;

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

      // Log activity
      await sql`
        INSERT INTO collection_activity (collection_id, user_id, action, details)
        VALUES (${id}, 1, 'permission_updated', ${JSON.stringify({ userId, role, status })})
      `;

      res.status(200).json(result.rows[0]);

    } catch (error) {
      console.error('Error updating permission:', error);
      res.status(500).json({ error: 'Internal server error' });
    }
  } else if (req.method === 'DELETE') {
    // Remove user permission
    try {
      const { userId } = req.body;

      if (!userId) {
        return res.status(400).json({ error: 'User ID is required' });
      }

      const result = await sql`
        DELETE FROM collection_permissions 
        WHERE collection_id = ${id} AND user_id = ${userId}
        RETURNING *
      `;

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

      // Log activity
      await sql`
        INSERT INTO collection_activity (collection_id, user_id, action, details)
        VALUES (${id}, 1, 'user_removed', ${JSON.stringify({ userId })})
      `;

      res.status(200).json({ message: 'Permission removed successfully' });

    } catch (error) {
      console.error('Error removing permission:', error);
      res.status(500).json({ error: 'Internal server error' });
    }
  } else {
    res.status(405).json({ error: 'Method not allowed' });
  }
}