// A small node:http stand-in for the SEO plugin's public API
// (/_seo/api/v1) and the Go binary's root files:
//
//   GET  /_seo/api/v1/resolve?url=…        the answer for that exact url from
//                                          <dir>/seo/resolve.json, then
//                                          <dir>/resolve.json, else not_found
//   GET  /_seo/api/v1/site                 <dir>/seo/site.json (404 without the
//                                          file or with { site: false }: an
//                                          older backend)
//   POST /_seo/api/v1/notfound             204 with `Authorization: Bearer <token>`,
//                                          401 with another token, 404 without one
//   GET  /_seo/api/v1/verification/<name>  <dir>/verification/<name> or
//                                          <dir>/seo/verification/<name>, else 404
//   GET  /robots.txt, /llms.txt,           <dir>/seo/root/<name>, else 404
//        /sitemap.xml
//   GET  /_sitemap/files/<file>            <dir>/seo/root/<file>, else 404;
//                                          sitemap-fail-*.xml answers 500
//   GET  /_sitemap/indexnow/<key>.txt      <dir>/seo/indexnow/<key>.txt, else 404
//
// It records every request (with the parsed JSON body of a POST) so a smoke
// run can assert header forwarding, resolve counts and the 404 reports.
// `reload()` reads the fixture files again (purge-check changes them).
//
// Plain .mjs with JSDoc types: Node does not strip TypeScript under
// node_modules, and consuming apps may import this file from there.

import { createServer } from 'node:http'
import { existsSync, readFileSync } from 'node:fs'
import { join } from 'node:path'

const PREFIX = '/_seo/api/v1'

/** The bearer token the fixture accepts on POST /notfound. */
export const FIXTURE_NOTFOUND_TOKEN = 'fixture-seo-notfound-token-0123456789'

/**
 * @typedef {{ method: string, url: string, xff: string | null, authorization: string | null, body: unknown }} FixtureRequest
 * @typedef {{ url: string, requests: FixtureRequest[], resolveCount: (target?: string) => number, reload: () => void, close: () => Promise<void> }} FixtureApi
 */

/** @param {string} file @returns {any} */
function readJson(file) {
  return existsSync(file) ? JSON.parse(readFileSync(file, 'utf8')) : null
}

/** @param {string} name */
function contentType(name) {
  if (name.endsWith('.xml')) return 'application/xml; charset=utf-8'
  if (name.endsWith('.html')) return 'text/html; charset=utf-8'
  return 'text/plain; charset=utf-8'
}

/**
 * Starts the fixture API on 127.0.0.1.
 * @param {{ dir: string, port?: number, token?: string, site?: boolean }} opts
 * @returns {Promise<FixtureApi>}
 */
export function startFixtureApi({ dir, port = 0, token = FIXTURE_NOTFOUND_TOKEN, site = true }) {
  /** @type {FixtureRequest[]} */
  const requests = []
  /** @type {Record<string, unknown>} */
  let answers = {}
  /** @type {unknown} */
  let siteAnswer = null
  const load = () => {
    answers = { ...(readJson(join(dir, 'resolve.json')) ?? {}), ...(readJson(join(dir, 'seo', 'resolve.json')) ?? {}) }
    siteAnswer = site ? readJson(join(dir, 'seo', 'site.json')) : null
  }
  load()

  /** @param {string} file @param {string} name */
  const fileAnswer = (file, name) => {
    if (/^sitemap-fail-/.test(name)) return { status: 500, text: 'backend failure', type: 'text/plain' }
    if (!existsSync(file)) return { status: 404, body: { error: 'not_found' } }
    return { status: 200, text: readFileSync(file, 'utf8'), type: contentType(name), robots: name.startsWith('sitemap-') || name === 'llms.txt' ? 'noindex' : undefined }
  }

  /**
   * @param {import('node:http').IncomingMessage} req
   * @returns {{ status: number, body?: unknown, text?: string, type?: string, robots?: string }}
   */
  const route = (req) => {
    const url = new URL(req.url ?? '/', 'http://fixture.local')
    const root = /^\/(robots\.txt|llms\.txt|sitemap\.xml)$/.exec(url.pathname)
    if (root && req.method === 'GET') return fileAnswer(join(dir, 'seo', 'root', root[1]), root[1])
    const files = /^\/_sitemap\/files\/(sitemap-[a-z0-9-]+\.xml)$/.exec(url.pathname)
    if (files && req.method === 'GET') return fileAnswer(join(dir, 'seo', 'root', files[1]), files[1])
    const key = /^\/_sitemap\/indexnow\/([A-Za-z0-9-]{8,128}\.txt)$/.exec(url.pathname)
    if (key && req.method === 'GET') return fileAnswer(join(dir, 'seo', 'indexnow', key[1]), key[1])
    if (!url.pathname.startsWith(PREFIX + '/')) return { status: 404, body: { error: 'not_found' } }
    const path = url.pathname.slice(PREFIX.length)
    if (path === '/resolve' && req.method === 'GET') {
      const target = url.searchParams.get('url') ?? ''
      if (!target.startsWith('/')) return { status: 422, body: { error: 'bad_url' } }
      const hit = answers[target]
      if (hit) return { status: 200, body: hit }
      return { status: 200, body: { action: 'not_found', status: 404, url: target, locale: '', staging: false, seo: null } }
    }
    if (path === '/site' && req.method === 'GET') {
      return siteAnswer ? { status: 200, body: siteAnswer } : { status: 404, body: { error: 'not_found' } }
    }
    if (path === '/notfound' && req.method === 'POST') {
      if (!token) return { status: 404, body: { error: 'not_found' } }
      return req.headers.authorization === `Bearer ${token}` ? { status: 204 } : { status: 401, body: { error: 'unauthorized' } }
    }
    const v = /^\/verification\/([A-Za-z0-9._-]+)$/.exec(path)
    if (v && req.method === 'GET') {
      for (const file of [join(dir, 'verification', v[1]), join(dir, 'seo', 'verification', v[1])]) {
        if (existsSync(file)) return { status: 200, text: readFileSync(file, 'utf8'), type: 'text/html; charset=utf-8' }
      }
      return { status: 404, body: { error: 'not_found' } }
    }
    return { status: 404, body: { error: 'not_found' } }
  }

  const server = createServer((req, res) => {
    const chunks = /** @type {Buffer[]} */ ([])
    req.on('data', (c) => chunks.push(c))
    req.on('end', () => {
      const raw = Buffer.concat(chunks).toString('utf8')
      let body = null
      try {
        body = raw ? JSON.parse(raw) : null
      } catch {
        body = raw
      }
      const header = (/** @type {string} */ name) => {
        const v = req.headers[name]
        return Array.isArray(v) ? v.join(', ') : (v ?? null)
      }
      requests.push({ method: req.method ?? 'GET', url: req.url ?? '/', xff: header('x-forwarded-for'), authorization: header('authorization'), body })
      let out
      try {
        out = route(req)
      } catch (err) {
        out = { status: 500, body: { error: String(err) } }
      }
      if (out.text !== undefined) {
        res.writeHead(out.status, { 'content-type': out.type ?? 'text/plain', ...(out.robots ? { 'x-robots-tag': out.robots } : {}) })
        res.end(out.text)
        return
      }
      res.writeHead(out.status, out.body === undefined ? {} : { 'content-type': 'application/json' })
      res.end(out.body === undefined ? undefined : JSON.stringify(out.body))
    })
  })

  /** Resolve calls so far, for one target url or (without one) all of them. @param {string} [target] */
  const resolveCount = (target) =>
    requests.filter((r) => {
      if (r.method !== 'GET') return false
      const u = new URL(r.url, 'http://fixture.local')
      return u.pathname === `${PREFIX}/resolve` && (target === undefined || u.searchParams.get('url') === target)
    }).length

  return new Promise((resolve, reject) => {
    server.once('error', reject)
    server.listen(port, '127.0.0.1', () => {
      const addr = /** @type {import('node:net').AddressInfo} */ (server.address())
      resolve({
        url: `http://127.0.0.1:${addr.port}`,
        requests,
        resolveCount,
        reload: load,
        close: () => new Promise((done) => server.close(() => done())),
      })
    })
  })
}