import type { NextApiRequest, NextApiResponse } from 'next'
import bcrypt from 'bcryptjs'
import { createUser, findUserByEmail } from './[...nextauth]'
import { UserRole, AuthResponse, RegisterInput } from '@/lib/auth/types'
import { withRateLimit } from '@/lib/auth/withAuth'

const BCRYPT_ROUNDS = 12 // Secure password hashing

async function handler(
  req: NextApiRequest,
  res: NextApiResponse<AuthResponse>
) {
  if (req.method !== 'POST') {
    return res.status(405).json({
      success: false,
      message: 'Method not allowed',
      error: 'Only POST requests are accepted',
    })
  }

  try {
    const { email, password, name, role }: RegisterInput = req.body

    // Validation
    if (!email || !password) {
      return res.status(400).json({
        success: false,
        message: 'Email and password are required',
        error: 'VALIDATION_ERROR',
      })
    }

    // Email format validation
    const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/
    if (!emailRegex.test(email)) {
      return res.status(400).json({
        success: false,
        message: 'Invalid email format',
        error: 'INVALID_EMAIL',
      })
    }

    // Password strength validation
    if (password.length < 8) {
      return res.status(400).json({
        success: false,
        message: 'Password must be at least 8 characters long',
        error: 'WEAK_PASSWORD',
      })
    }

    // Check password complexity
    const hasUpperCase = /[A-Z]/.test(password)
    const hasLowerCase = /[a-z]/.test(password)
    const hasNumbers = /\d/.test(password)

    if (!hasUpperCase || !hasLowerCase || !hasNumbers) {
      return res.status(400).json({
        success: false,
        message: 'Password must contain uppercase, lowercase, and numbers',
        error: 'WEAK_PASSWORD',
      })
    }

    // Check if user already exists
    const existingUser = findUserByEmail(email)
    if (existingUser) {
      return res.status(409).json({
        success: false,
        message: 'An account with this email already exists',
        error: 'USER_EXISTS',
      })
    }

    // Hash password with bcrypt
    const passwordHash = await bcrypt.hash(password, BCRYPT_ROUNDS)

    // Determine role (default to USER, only admin can assign higher roles)
    // In a real app, you'd check if the requester has admin permissions
    const userRole = role === UserRole.ADMIN ? UserRole.USER : (role || UserRole.USER)

    // Create user
    const user = createUser({
      email: email.toLowerCase(),
      name: name || undefined,
      passwordHash,
      role: userRole,
    })

    // TODO: Send verification email (will be implemented with Agent 8 - Notifications)
    console.log(`New user registered: ${user.email}`)

    return res.status(201).json({
      success: true,
      message: 'Registration successful. Please sign in.',
      user: {
        id: user.id,
        email: user.email,
        name: user.name,
        role: user.role,
        image: user.image,
        emailVerified: user.emailVerified,
      },
    })
  } catch (error) {
    console.error('Registration error:', error)
    return res.status(500).json({
      success: false,
      message: 'An error occurred during registration',
      error: 'INTERNAL_ERROR',
    })
  }
}

// Apply rate limiting: 5 registrations per minute per IP
export default withRateLimit(handler, {
  limit: 5,
  windowMs: 60000,
})