'use strict'
const http = require('node:http')
const path = require('node:path')
const fs = require('node:fs')
const crypto = require('node:crypto')
const { initDb } = require('./db.js')
const { sendMagicLink } = require('./mailer.js')

const PORT = parseInt(process.env.PORT || '3001', 10)
const DB_PATH = process.env.DB_PATH || undefined

const DIST_DIR = path.join(__dirname, '../client/dist')

function send(res, status, body) {
  res.writeHead(status, { 'Content-Type': 'application/json' })
  res.end(JSON.stringify(body))
}

function readBody(req) {
  return new Promise((resolve, reject) => {
    let data = ''
    req.on('error', reject)
    req.on('data', c => {
      data += c
      if (data.length > 1024 * 1024) {
        req.destroy(new Error('body too large'))
      }
    })
    req.on('end', () => {
      try { resolve(JSON.parse(data)) }
      catch { resolve({}) }
    })
  })
}

function createServer(db) {
  if (!db) {
    db = initDb(DB_PATH)
  }

  function requireAuth(req, res) {
    const auth = req.headers['authorization'] || ''
    const token = auth.startsWith('Bearer ') ? auth.slice(7) : null
    if (!token) { send(res, 401, { error: 'unauthorized' }); return null }
    const session = db.getSession(token)
    if (!session) { send(res, 401, { error: 'unauthorized' }); return null }
    return session
  }

  function requireAdmin(req, res) {
    const pwd = process.env.ADMIN_PASSWORD
    const auth = req.headers['authorization'] || ''
    const token = auth.startsWith('Bearer ') ? auth.slice(7) : null
    if (!pwd || token !== pwd) { send(res, 401, { error: 'unauthorized' }); return false }
    return true
  }

  async function handleRequest(req, res) {
    const url = new URL(req.url, 'http://127.0.0.1')
    const pathname = url.pathname
    const method = req.method

    // ── Auth routes ──────────────────────────────────────────────────────────

    if (pathname === '/api/auth/guest' && method === 'POST') {
      const body = await readBody(req)
      const name = body.display_name
      if (!name || typeof name !== 'string' || name.trim().length < 2 || name.trim().length > 80) {
        return send(res, 400, { error: 'display_name required (2-80 chars)' })
      }
      const profile = db.createGuestProfile(name.trim())
      db.getOrCreateProgress(profile.id)
      const sessionToken = crypto.randomBytes(32).toString('hex')
      db.createSession(sessionToken, profile.id)
      return send(res, 200, {
        token: sessionToken,
        profile: { id: profile.id, email: null, display_name: profile.display_name, is_guest: true },
      })
    }

    if (pathname === '/api/auth/request' && method === 'POST') {
      const body = await readBody(req)
      const email = body.email
      if (!email || typeof email !== 'string' || !email.includes('@') || !email.includes('.')) {
        return send(res, 400, { error: 'email required' })
      }
      let profile = db.findProfileByEmail(email)
      if (!profile) {
        profile = db.createProfile(email, null)
      }
      const token = crypto.randomBytes(32).toString('hex')
      const expiresAt = Date.now() + 24 * 60 * 60 * 1000
      db.createMagicToken(token, profile.id, expiresAt)
      await sendMagicLink(email, token).catch(err => {
        // Log SMTP errors but don't fail the request — token is in DB, link logged
        console.error('[server] email send failed:', err.message ?? err)
      })
      return send(res, 200, { ok: true })
    }

    if (pathname === '/api/auth/verify' && method === 'GET') {
      const token = url.searchParams.get('token')
      if (!token) { return send(res, 400, { error: 'token required' }) }
      const profileId = db.useMagicToken(token)
      if (!profileId) { return send(res, 400, { error: 'invalid or expired token' }) }
      const sessionToken = crypto.randomBytes(32).toString('hex')
      db.createSession(sessionToken, profileId)
      res.writeHead(302, { Location: `/?session=${sessionToken}` })
      return res.end()
    }

    if (pathname === '/api/auth/me' && method === 'GET') {
      const session = requireAuth(req, res)
      if (!session) return
      const profile = db.findProfileById(session.profile_id)
      if (!profile) { return send(res, 404, { error: 'not found' }) }
      return send(res, 200, {
        id: profile.id,
        email: profile.email,
        display_name: profile.display_name,
        is_guest: profile.is_guest === 1,
      })
    }

    if (pathname === '/api/auth/session' && method === 'DELETE') {
      const session = requireAuth(req, res)
      if (!session) return
      db.deleteSession(session.token)
      return send(res, 200, { ok: true })
    }

    // ── Progress routes ───────────────────────────────────────────────────────

    if (pathname === '/api/progress' && method === 'GET') {
      const session = requireAuth(req, res)
      if (!session) return
      const progress = db.getOrCreateProgress(session.profile_id)
      return send(res, 200, progress)
    }

    if (pathname === '/api/progress/answer' && method === 'POST') {
      const session = requireAuth(req, res)
      if (!session) return
      const body = await readBody(req)
      const letter = typeof body.letter === 'string' ? body.letter.toUpperCase() : ''
      if (!/^[A-Z]$/.test(letter)) {
        return send(res, 400, { error: 'letter must be a single letter A-Z' })
      }
      if (typeof body.correct !== 'boolean') {
        return send(res, 400, { error: 'correct required' })
      }
      const progress = db.recordAnswer(session.profile_id, letter, body.correct)
      return send(res, 200, progress)
    }

    if (pathname === '/api/mnemonics' && method === 'GET') {
      const session = requireAuth(req, res)
      if (!session) return
      const mnemonics = db.getMnemonics(session.profile_id)
      return send(res, 200, mnemonics)
    }

    if (pathname === '/api/mnemonics' && method === 'POST') {
      const session = requireAuth(req, res)
      if (!session) return
      const body = await readBody(req)
      const letter = typeof body.letter === 'string' ? body.letter.toUpperCase() : ''
      if (!/^[A-Z]$/.test(letter)) {
        return send(res, 400, { error: 'letter must be a single letter A-Z' })
      }
      if (!body.phrase || typeof body.phrase !== 'string' || body.phrase.length > 500) {
        return send(res, 400, { error: 'phrase required (max 500 chars)' })
      }
      db.saveMnemonic(session.profile_id, letter, body.phrase)
      return send(res, 200, { ok: true })
    }

    // ── Admin routes ──────────────────────────────────────────────────────────

    if (pathname === '/api/admin/users' && method === 'GET') {
      if (!requireAdmin(req, res)) return
      const users = db.getAdminUsers()
      return send(res, 200, users)
    }

    if (pathname === '/api/admin/stats' && method === 'GET') {
      if (!requireAdmin(req, res)) return
      const stats = db.getAdminStats()
      return send(res, 200, stats)
    }

    // ── Unknown /api/* ────────────────────────────────────────────────────────

    if (pathname.startsWith('/api/')) {
      return send(res, 404, { error: 'not found' })
    }

    // ── Static files (SPA) ───────────────────────────────────────────────────

    // Prevent path traversal — ensure resolved path stays within DIST_DIR
    const relative = pathname.replace(/^\/+/, '')
    const filePath = path.join(DIST_DIR, relative)
    if (!filePath.startsWith(DIST_DIR + path.sep) && filePath !== DIST_DIR) {
      return send(res, 400, { error: 'bad request' })
    }

    if (fs.existsSync(filePath) && fs.statSync(filePath).isFile()) {
      const ext = path.extname(filePath)
      const mimeTypes = {
        '.html': 'text/html',
        '.js': 'application/javascript',
        '.css': 'text/css',
        '.json': 'application/json',
        '.png': 'image/png',
        '.jpg': 'image/jpeg',
        '.svg': 'image/svg+xml',
        '.ico': 'image/x-icon',
      }
      const contentType = mimeTypes[ext] || 'application/octet-stream'
      res.writeHead(200, { 'Content-Type': contentType })
      return fs.createReadStream(filePath).pipe(res)
    }

    // SPA fallback — serve index.html
    const indexPath = path.join(DIST_DIR, 'index.html')
    if (fs.existsSync(indexPath)) {
      res.writeHead(200, { 'Content-Type': 'text/html' })
      return fs.createReadStream(indexPath).pipe(res)
    }

    // No dist yet
    return send(res, 404, { error: 'not found' })
  }

  const server = http.createServer((req, res) => {
    handleRequest(req, res).catch(err => {
      console.error('[server] unhandled:', err)
      if (!res.headersSent) { res.writeHead(500); res.end() }
    })
  })

  return server
}

if (require.main === module) {
  const db = initDb(DB_PATH)
  const server = createServer(db)
  server.listen(PORT, () => console.log(`[server] listening on :${PORT}`))
}

module.exports = { createServer }