// Resolves every page request through the CMS (resolveCached: LRU and the
// visitor's X-Forwarded-For) and enforces the decision before Nuxt renders
// the page and before Nitro's route cache, so swr-cached pages honour a new
// redirect or 410:
//
//   redirect   301 or 302 with Location from the answer (seoRedirectTarget:
//              a target on the site's own origin becomes a path, another
//              host stays absolute); nothing from the request (Host, path,
//              query) ever goes into the Location
//   gone       410 with the app's error page
//   not_found  left to Nuxt's routing, except a pagination.invalid answer
//              (?page=abc), which is a 404
//
// X-Robots-Tag follows the answer (staging: noindex, nofollow everywhere;
// else the page's x_robots_tag), never on a redirect. Skipped: Nuxt's and
// the layers' internal paths (/_nuxt, /__nuxt_error, /_seo …), /api and
// asset files (isPagePath). The answer stays in event.context.seo for the
// render, which then makes no second call (useSeoResolve). With the CMS
// unreachable the page renders normally (fail open).

import { isPagePath } from '../../app/utils/pagePath.ts'
import { seoRedirectTarget, seoXRobotsTag } from '../../app/utils/seo.ts'
import { seoServerConfig } from '../lib/config.ts'
import { resolveCached } from '../lib/resolve.ts'

export default defineEventHandler(async (event) => {
  if (event.method !== 'GET' && event.method !== 'HEAD') return
  const cfg = seoServerConfig(useRuntimeConfig(event))
  if (!cfg.enabled) return
  const url = event.path
  if (!isPagePath(url, cfg.resolveFiles)) return

  const answer = await resolveCached(event, url)
  event.context.seo = answer
  event.context.seoResolved = { url, answer }
  if (!answer) return

  const target = seoRedirectTarget(answer)
  if (target) return sendRedirect(event, target.to, target.code)

  const robots = seoXRobotsTag(answer)
  if (robots) setResponseHeader(event, 'x-robots-tag', robots)
  if (answer.action === 'gone') throw createError({ statusCode: 410, statusMessage: 'Gone' })
  if (answer.action === 'not_found' && answer.pagination?.invalid === true) {
    throw createError({ statusCode: 404, statusMessage: 'Page Not Found' })
  }
})