import { NextRequest, NextResponse } from 'next/server'
import { getSessionOptions, hashPassword, type SessionData } from '@/lib/auth'
import { getIronSession } from 'iron-session'
import { getUserCount, createUser } from '@/lib/users'

export async function POST(request: NextRequest) {
  let body: { username?: string; password?: string; role?: string }
  try {
    body = await request.json()
  } catch {
    return NextResponse.json({ error: 'Invalid JSON body' }, { status: 400 })
  }

  const { username, password } = body
  let { role } = body

  if (!username || !password) {
    return NextResponse.json({ error: 'username and password are required' }, { status: 400 })
  }
  if (username.trim().length < 2) {
    return NextResponse.json({ error: 'Username must be at least 2 characters' }, { status: 400 })
  }
  if (password.length < 8) {
    return NextResponse.json({ error: 'Password must be at least 8 characters' }, { status: 400 })
  }

  const userCount = getUserCount()

  if (userCount === 0) {
    // First user always becomes admin
    role = 'admin'
  } else {
    // Subsequent users require an admin session
    const res = new NextResponse()
    const session = await getIronSession<SessionData>(request, res, getSessionOptions())
    if (!session.userId) {
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
    }
    if (session.role !== 'admin') {
      return NextResponse.json({ error: 'Forbidden' }, { status: 403 })
    }
    if (role !== 'admin' && role !== 'user') {
      role = 'user'
    }
  }

  const passwordHash = await hashPassword(password)

  try {
    const user = createUser(username.trim(), passwordHash, role as 'admin' | 'user')
    return NextResponse.json({ id: user.id, username: user.username, role: user.role }, { status: 201 })
  } catch (err) {
    const message = err instanceof Error ? err.message : 'Failed to create user'
    if (message.includes('UNIQUE constraint failed')) {
      return NextResponse.json({ error: 'Username already taken' }, { status: 409 })
    }
    return NextResponse.json({ error: message }, { status: 400 })
  }
}