/**
 * Geheimer Vorschau-Link (2026-10-26): Wer den Link kennt, sieht die Preview-Seite eines Projekts
 * ohne Login. Der Link ist nirgends verlinkt, nur Mitarbeiter sehen ihn im Ticket.
 *
 * Ablauf:
 *   1. WOMS erzeugt den Link (POST /api/admin/website-projects/:id/vorschau-link) -> websiteProjects.shareToken
 *   2. Besucher oeffnet https://project.webklar.com/vorschau/<subdomain>/<token>
 *      -> Cookie wk_vorschau_<subdomain>=<token> fuer .project.webklar.com, Weiterleitung auf die Subdomain
 *   3. Die Login-Pruefung der Previews (preview-portal /auth/verify) fragt bei jedem Aufruf
 *      GET /api/vorschau-link/pruefen?subdomain=... mit dem Cookie-Wert im Header x-vorschau-token
 *
 * Ein neuer Link oder "Abschalten" macht alte Links und Cookies sofort ungueltig (nach hoechstens CACHE_MS).
 */
import crypto from 'node:crypto'
import { config } from '../config.js'
import { getDocument, listDocuments, updateDocument, Query } from './appwriteAdmin.js'
import { isPreviewProjectReady } from './previewReadiness.js'

export const COOKIE_PREFIX = 'wk_vorschau_'
export const COOKIE_MAX_AGE_SEC = 30 * 24 * 60 * 60
const CACHE_MS = 15 * 1000
const SUBDOMAIN = /^[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?$/
const TOKEN = /^[A-Za-z0-9_-]{20,64}$/

export function newShareToken() {
  return crypto.randomBytes(18).toString('base64url')
}

export function cleanSubdomain(value) {
  const s = String(value || '').trim().toLowerCase()
  return SUBDOMAIN.test(s) ? s : ''
}

export function cleanToken(value) {
  const t = String(value || '').trim()
  return TOKEN.test(t) ? t : ''
}

export function cookieName(subdomain) {
  return `${COOKIE_PREFIX}${subdomain}`
}

export function shareUrl(subdomain, token) {
  return `${config.publicBaseUrl}/vorschau/${subdomain}/${token}`
}

export function previewUrl(subdomain) {
  return `https://${subdomain}.${config.preview.baseHost}/`
}

export function shareCookieOptions() {
  return {
    domain: config.preview.cookieDomain,
    path: '/',
    httpOnly: true,
    secure: process.env.NODE_ENV === 'production',
    sameSite: 'lax',
    maxAge: COOKIE_MAX_AGE_SEC * 1000,
  }
}

function sameToken(a, b) {
  const x = Buffer.from(String(a))
  const y = Buffer.from(String(b))
  return x.length === y.length && crypto.timingSafeEqual(x, y)
}

// Die Pruefung laeuft bei jedem Bild/Skript der Seite: kurz merken statt jedes Mal Appwrite fragen
const cache = new Map()

export function clearShareCache() {
  cache.clear()
}

async function projectBySubdomain(subdomain) {
  const hit = cache.get(subdomain)
  if (hit && hit.until > Date.now()) return hit.project
  const docs = await listDocuments(config.collections.websiteProjects, [
    Query.equal('subdomain', subdomain),
    Query.limit(1),
  ])
  const project = docs[0] || null
  cache.set(subdomain, { project, until: Date.now() + CACHE_MS })
  if (cache.size > 500) cache.delete(cache.keys().next().value)
  return project
}

/** { allowed, reason } - reason: bad_request | no_link | not_ready */
export async function checkShare(subdomainRaw, tokenRaw) {
  const subdomain = cleanSubdomain(subdomainRaw)
  const token = cleanToken(tokenRaw)
  if (!subdomain || !token) return { allowed: false, reason: 'bad_request' }
  const project = await projectBySubdomain(subdomain)
  if (!project || project.archived || !project.shareToken || !sameToken(project.shareToken, token)) {
    return { allowed: false, reason: 'no_link' }
  }
  if (!isPreviewProjectReady(project)) return { allowed: false, reason: 'not_ready' }
  return { allowed: true, subdomain }
}

/** Neuer Link (ersetzt einen alten). Wirft 404/409 mit status. */
export async function renewShareLink(projectId) {
  const project = await getDocument(config.collections.websiteProjects, projectId).catch(() => null)
  if (!project) throw Object.assign(new Error('Projekt nicht gefunden'), { status: 404 })
  const subdomain = cleanSubdomain(project.subdomain)
  if (!subdomain) throw Object.assign(new Error('Das Projekt hat keine Preview-Subdomain.'), { status: 409 })
  const token = newShareToken()
  await updateDocument(config.collections.websiteProjects, projectId, { shareToken: token })
  clearShareCache()
  return { shareToken: token, url: shareUrl(subdomain, token) }
}

export async function removeShareLink(projectId) {
  const project = await getDocument(config.collections.websiteProjects, projectId).catch(() => null)
  if (!project) throw Object.assign(new Error('Projekt nicht gefunden'), { status: 404 })
  await updateDocument(config.collections.websiteProjects, projectId, { shareToken: '' })
  clearShareCache()
  return { shareToken: '' }
}