import { Router } from 'express'
import { readFileSync, writeFileSync, existsSync } from 'fs'
import { join, dirname } from 'path'
import { fileURLToPath } from 'url'
import { Mutex } from 'async-mutex'
import { resourceLimiter } from '../middleware/rateLimiter.js'
import { antiSpam } from '../middleware/antiSpam.js'

const __dirname = dirname(fileURLToPath(import.meta.url))
const LEADS_FILE = join(__dirname, '..', 'data', 'leads.json')
const leadsMutex = new Mutex()

// Only alphanumeric + hyphen resource IDs are allowed. This prevents path
// traversal (e.g. "../../etc/passwd") when building the download URL.
const RESOURCE_ID_PATTERN = /^[a-z0-9]+(-[a-z0-9]+)*$/

function loadLeads() {
  if (!existsSync(LEADS_FILE)) return []
  try { return JSON.parse(readFileSync(LEADS_FILE, 'utf-8')) }
  catch { return [] }
}

function saveLeads(leads) {
  writeFileSync(LEADS_FILE, JSON.stringify(leads, null, 2), 'utf-8')
}

const router = Router()

router.post('/', resourceLimiter, antiSpam, async (req, res) => {
  const { name, email, company, resource_id } = req.body
  const errors = {}
  if (!name || name.trim().length === 0) errors.name = 'Name ist erforderlich.'
  if (name && name.length > 100) errors.name = 'Max. 100 Zeichen.'
  if (!email || !/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(email)) errors.email = 'Gültige E-Mail erforderlich.'
  if (!company || company.trim().length === 0) errors.company = 'Unternehmen ist erforderlich.'
  if (company && company.length > 150) errors.company = 'Max. 150 Zeichen.'
  if (!resource_id || !RESOURCE_ID_PATTERN.test(resource_id)) errors.resource_id = 'Ungültige Resource-ID.'

  if (Object.keys(errors).length > 0) {
    return res.status(400).json({ errors })
  }

  await leadsMutex.runExclusive(async () => {
    const leads = loadLeads()
    leads.push({
      name,
      email,
      company,
      resource_id,
      timestamp: new Date().toISOString(),
    })
    saveLeads(leads)
  })

  // Return download URL (resource files are in public/resources/)
  res.json({ ok: true, download_url: `/resources/${resource_id}.pdf` })
})

export default router