const express = require('express')
const bcrypt = require('bcryptjs')
const { z } = require('zod')
const { nanoid } = require('nanoid')
const multer = require('multer')
const {
  countUsers,
  findUserByEmail,
  findUserById,
  createUser,
  updateUserProfile,
  findPrimaryAdminUser,
} = require('../db')
const { requireAuth } = require('../middleware/auth')
const { createMemoryUpload, writeOptimizedImage } = require('../lib/image-storage')

const router = express.Router()

const signupSchema = z.object({
  email: z.string().email(),
  password: z.string().min(6),
})

const profileSchema = z.object({
  nickname: z.string().trim().min(1).max(40),
  removeAvatar: z.union([z.string(), z.undefined()]).optional(),
})

function establishSession(req, user) {
  return new Promise((resolve, reject) => {
    req.session.regenerate((regenerateError) => {
      if (regenerateError) return reject(regenerateError)
      req.session.userId = user.id
      req.session.isAdmin = !!user.isAdmin
      req.session.save((saveError) => {
        if (saveError) return reject(saveError)
        resolve()
      })
    })
  })
}

async function serializeUser(user) {
  if (!user) return null
  const primaryAdmin = await findPrimaryAdminUser()
  const isPrimaryAdmin = !!user.isAdmin && primaryAdmin?.id === user.id

  return {
    id: user.id,
    email: user.email,
    nickname: user.nickname || '',
    isAdmin: !!user.isAdmin,
    isPrimaryAdmin,
    isOperator: !!user.isAdmin && !isPrimaryAdmin,
    role: isPrimaryAdmin ? 'owner' : user.isAdmin ? 'operator' : 'user',
    avatarSrc: user.avatarSrc || '',
    createdAt: user.createdAt,
  }
}

router.post('/signup', async (req, res) => {
  const parsed = signupSchema.safeParse(req.body)
  if (!parsed.success) return res.status(400).json({ error: 'bad_request' })

  const { email, password } = parsed.data
  const exists = await findUserByEmail(email)
  if (exists) return res.status(409).json({ error: 'email_taken' })

  const passwordHash = await bcrypt.hash(password, 10)
  const isAdmin = (await countUsers()) === 0
  const user = await createUser({ id: nanoid(), email, nickname: '', passwordHash, isAdmin })

  try {
    await establishSession(req, user)
    res.json(await serializeUser(user))
  } catch (err) {
    return res.status(500).json({ error: 'session_save_failed' })
  }
})

router.post('/login', async (req, res) => {
  const parsed = signupSchema.safeParse(req.body)
  if (!parsed.success) return res.status(400).json({ error: 'bad_request' })

  const { email, password } = parsed.data
  const user = await findUserByEmail(email)
  if (!user) return res.status(401).json({ error: 'invalid_credentials' })

  const ok = await bcrypt.compare(password, user.passwordHash)
  if (!ok) return res.status(401).json({ error: 'invalid_credentials' })

  try {
    await establishSession(req, user)
    res.json(await serializeUser(user))
  } catch (err) {
    return res.status(500).json({ error: 'session_save_failed' })
  }
})

router.post('/logout', async (req, res) => {
  if (!req.session) return res.json({ ok: true })
  req.session.destroy(() => res.json({ ok: true }))
})

router.get('/me', async (req, res) => {
  if (!req.session || !req.session.userId) return res.json({ user: null })
  const user = await findUserById(req.session.userId)
  if (!user) return res.json({ user: null })
  res.json({ user: await serializeUser(user) })
})

router.get('/meta', async (req, res) => {
  res.json({ hasUsers: (await countUsers()) > 0 })
})

const upload = createMemoryUpload(multer, { fileSize: 4 * 1024 * 1024 })

router.post('/profile', requireAuth, upload.single('avatar'), async (req, res) => {
  const parsed = profileSchema.safeParse(req.body)
  if (!parsed.success) return res.status(400).json({ error: 'bad_request' })

  const user = await findUserById(req.session.userId)
  if (!user) return res.status(404).json({ error: 'not_found' })

  const optimized = req.file
    ? await writeOptimizedImage({
        file: req.file,
        directory: 'avatars',
        width: 512,
        height: 512,
        fit: 'cover',
        quality: 82,
      })
    : null

  const shouldRemoveAvatar = parsed.data.removeAvatar === '1'
  const nextAvatarSrc = shouldRemoveAvatar ? '' : optimized?.src || user.avatarSrc || ''
  const updated = await updateUserProfile({
    id: user.id,
    nickname: parsed.data.nickname,
    avatarSrc: nextAvatarSrc,
  })

  res.json({ user: await serializeUser(updated) })
})

module.exports = router