import { NextRequest, NextResponse } from 'next/server';
import { Pool } from 'pg';
import jwt from 'jsonwebtoken';

const pool = new Pool({
  connectionString: process.env.DATABASE_URL,
  ssl: process.env.NODE_ENV === 'production' ? { rejectUnauthorized: false } : false,
});

// Middleware to verify admin access
async function verifyAdmin(req: NextRequest) {
  const authHeader = req.headers.get('authorization');
  if (!authHeader?.startsWith('Bearer ')) {
    throw new Error('No token provided');
  }

  const token = authHeader.substring(7);
  const jwtSecret = process.env.JWT_SECRET || 'fallback-secret-change-in-production';
  
  try {
    const decoded = jwt.verify(token, jwtSecret) as any;
    
    // Check if user has admin role
    if (!decoded.roles?.includes('admin')) {
      throw new Error('Admin access required');
    }
    
    return decoded;
  } catch (error) {
    throw new Error('Invalid token or insufficient permissions');
  }
}

export default async function handler(req: NextRequest) {
  const client = await pool.connect();
  
  try {
    // Verify admin access
    await verifyAdmin(req);

    if (req.method === 'GET') {
      // Get all users with their roles
      const { searchParams } = new URL(req.url);
      const page = parseInt(searchParams.get('page') || '1');
      const limit = parseInt(searchParams.get('limit') || '20');
      const search = searchParams.get('search') || '';
      const offset = (page - 1) * limit;

      let whereClause = '';
      let queryParams: any[] = [limit, offset];
      
      if (search) {
        whereClause = 'WHERE u.username ILIKE $3 OR u.email ILIKE $3 OR u.first_name ILIKE $3 OR u.last_name ILIKE $3';
        queryParams.push(`%${search}%`);
      }

      const usersResult = await client.query(`
        SELECT 
          u.id, u.username, u.email, u.first_name, u.last_name, 
          u.is_active, u.email_verified, u.created_at, u.last_login,
          array_agg(r.name) as roles
        FROM users u
        LEFT JOIN user_roles ur ON u.id = ur.user_id
        LEFT JOIN roles r ON ur.role_id = r.id
        ${whereClause}
        GROUP BY u.id, u.username, u.email, u.first_name, u.last_name, 
                 u.is_active, u.email_verified, u.created_at, u.last_login
        ORDER BY u.created_at DESC
        LIMIT $1 OFFSET $2
      `, queryParams);

      // Get total count for pagination
      const countResult = await client.query(`
        SELECT COUNT(DISTINCT u.id) as total
        FROM users u
        ${whereClause.replace('$3', search ? '$1' : '')}
      `, search ? [`%${search}%`] : []);

      return new NextResponse(JSON.stringify({
        success: true,
        users: usersResult.rows.map(user => ({
          ...user,
          roles: user.roles.filter(Boolean) // Remove null values
        })),
        pagination: {
          page,
          limit,
          total: parseInt(countResult.rows[0].total),
          totalPages: Math.ceil(countResult.rows[0].total / limit)
        }
      }), {
        status: 200,
        headers: { 'Content-Type': 'application/json' },
      });

    } else if (req.method === 'PUT') {
      // Update user (activate/deactivate, change roles)
      const { searchParams } = new URL(req.url);
      const userId = searchParams.get('id');
      
      if (!userId) {
        return new NextResponse(JSON.stringify({ error: 'User ID required' }), {
          status: 400,
          headers: { 'Content-Type': 'application/json' },
        });
      }

      // Parse request body
      let body: { isActive?: boolean; roles?: string[] };
      try {
        const bodyText = await req.text();
        body = JSON.parse(bodyText);
      } catch (parseError) {
        return new NextResponse(JSON.stringify({ 
          error: 'Invalid JSON in request body' 
        }), {
          status: 400,
          headers: { 'Content-Type': 'application/json' },
        });
      }

      const { isActive, roles } = body;

      // Update user status
      if (typeof isActive === 'boolean') {
        await client.query(
          'UPDATE users SET is_active = $1, updated_at = CURRENT_TIMESTAMP WHERE id = $2',
          [isActive, userId]
        );
      }

      // Update user roles
      if (roles && Array.isArray(roles)) {
        // Remove existing roles
        await client.query('DELETE FROM user_roles WHERE user_id = $1', [userId]);
        
        // Add new roles
        for (const roleName of roles) {
          const roleResult = await client.query('SELECT id FROM roles WHERE name = $1', [roleName]);
          if (roleResult.rows.length > 0) {
            await client.query(
              'INSERT INTO user_roles (user_id, role_id) VALUES ($1, $2)',
              [userId, roleResult.rows[0].id]
            );
          }
        }
      }

      // Get updated user data
      const updatedUser = await client.query(`
        SELECT 
          u.id, u.username, u.email, u.first_name, u.last_name, 
          u.is_active, u.email_verified, u.created_at, u.last_login,
          array_agg(r.name) as roles
        FROM users u
        LEFT JOIN user_roles ur ON u.id = ur.user_id
        LEFT JOIN roles r ON ur.role_id = r.id
        WHERE u.id = $1
        GROUP BY u.id, u.username, u.email, u.first_name, u.last_name, 
                 u.is_active, u.email_verified, u.created_at, u.last_login
      `, [userId]);

      return new NextResponse(JSON.stringify({
        success: true,
        message: 'User updated successfully',
        user: {
          ...updatedUser.rows[0],
          roles: updatedUser.rows[0].roles.filter(Boolean)
        }
      }), {
        status: 200,
        headers: { 'Content-Type': 'application/json' },
      });

    } else if (req.method === 'DELETE') {
      // Delete user (soft delete by deactivating)
      const { searchParams } = new URL(req.url);
      const userId = searchParams.get('id');
      
      if (!userId) {
        return new NextResponse(JSON.stringify({ error: 'User ID required' }), {
          status: 400,
          headers: { 'Content-Type': 'application/json' },
        });
      }

      await client.query(
        'UPDATE users SET is_active = false, updated_at = CURRENT_TIMESTAMP WHERE id = $1',
        [userId]
      );

      return new NextResponse(JSON.stringify({
        success: true,
        message: 'User deactivated successfully'
      }), {
        status: 200,
        headers: { 'Content-Type': 'application/json' },
      });

    } else {
      return new NextResponse(JSON.stringify({ error: 'Method not allowed' }), {
        status: 405,
        headers: { 'Content-Type': 'application/json' },
      });
    }

  } catch (error) {
    console.error('Admin users API error:', error);
    
    if ((error as Error).message.includes('Admin access required') || 
        (error as Error).message.includes('No token provided') ||
        (error as Error).message.includes('Invalid token')) {
      return new NextResponse(JSON.stringify({ 
        error: 'Unauthorized',
        message: (error as Error).message
      }), {
        status: 401,
        headers: { 'Content-Type': 'application/json' },
      });
    }

    return new NextResponse(JSON.stringify({ 
      error: 'Internal server error',
      details: process.env.NODE_ENV === 'development' ? (error as Error).message : undefined
    }), {
      status: 500,
      headers: { 'Content-Type': 'application/json' },
    });
  } finally {
    client.release();
  }
}