import { readFile, writeFile } from 'node:fs/promises'

function normalizeBaseUrl(baseUrl) {
  return String(baseUrl || '').trim().replace(/\/$/, '') || 'https://hypertwist.app'
}

function uniqueTrimmedStrings(values) {
  const result = []
  const seen = new Set()

  for (const rawValue of Array.isArray(values) ? values : []) {
    const value = String(rawValue || '').trim()
    if (!value || seen.has(value)) {
      continue
    }

    seen.add(value)
    result.push(value)
  }

  return result
}

function readRoutePath(route) {
  const path = String(route?.path || '').trim()
  return path || null
}

export function buildPublicSearchAssetPlan(routeRegistry, policy = {}) {
  const sanitizedRoutes = Array.isArray(routeRegistry) ? routeRegistry.filter((route) => readRoutePath(route)) : []
  const crawlableRoutes = sanitizedRoutes.filter((route) => route?.crawlable === true)
  const nonCrawlablePaths = sanitizedRoutes
    .filter((route) => route?.crawlable !== true)
    .map((route) => readRoutePath(route))
    .filter(Boolean)

  const explicitDisallowPaths = uniqueTrimmedStrings(policy?.explicitDisallowPaths)
  const crawlerDisallowPaths = uniqueTrimmedStrings([
    ...explicitDisallowPaths,
    ...nonCrawlablePaths,
  ])

  return {
    baseUrl: normalizeBaseUrl(policy?.baseUrl),
    crawlableRoutes,
    crawlerDisallowPaths,
  }
}

export function buildPublicSitemapXml(routeRegistry, policy = {}) {
  const { baseUrl, crawlableRoutes } = buildPublicSearchAssetPlan(routeRegistry, policy)
  const urlEntries = crawlableRoutes
    .map((route) => `  <url>\n    <loc>${baseUrl}${route.path === '/' ? '/' : route.path}</loc>\n  </url>`)
    .join('\n')

  return `<?xml version="1.0" encoding="UTF-8"?>\n<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">\n${urlEntries}\n</urlset>\n`
}

export function buildPublicRobotsTxt(routeRegistry, policy = {}) {
  const { baseUrl, crawlerDisallowPaths } = buildPublicSearchAssetPlan(routeRegistry, policy)

  return [
    'User-agent: *',
    'Allow: /',
    ...crawlerDisallowPaths.map((path) => `Disallow: ${path}`),
    '',
    `Sitemap: ${baseUrl}/sitemap.xml`,
    '',
  ].join('\n')
}

export async function loadPublicSearchAssetInputs({ registryPath, policyPath }) {
  const [routeRegistry, policy] = await Promise.all([
    readFile(registryPath, 'utf8').then((content) => JSON.parse(content)),
    readFile(policyPath, 'utf8').then((content) => JSON.parse(content)),
  ])

  return { routeRegistry, policy }
}

export async function renderPublicSearchAssets({
  registryPath,
  policyPath,
  sitemapPath,
  robotsPath,
}) {
  const { routeRegistry, policy } = await loadPublicSearchAssetInputs({
    registryPath,
    policyPath,
  })

  const plan = buildPublicSearchAssetPlan(routeRegistry, policy)
  const sitemapXml = buildPublicSitemapXml(routeRegistry, policy)
  const robotsTxt = buildPublicRobotsTxt(routeRegistry, policy)

  await Promise.all([
    writeFile(sitemapPath, sitemapXml, 'utf8'),
    writeFile(robotsPath, robotsTxt, 'utf8'),
  ])

  return {
    ...plan,
    sitemapXml,
    robotsTxt,
  }
}