/**
 * Dev : sert chaque dist-<slug>/ sous /slides/<slug>/ (sources = dossiers à la racine du dépôt).
 * La racine `/slides/<slug>/` (et `/slides/<slug>`) redirige en 302 vers `/slides/<slug>/1` (route Slidev).
 */
import fs from 'node:fs'
import path from 'node:path'
import { fileURLToPath } from 'node:url'
import sirv from 'sirv'
import { listPresentationSlugs } from '../../tools/list-slugs.mjs'

const repoRoot = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '../..')

function slidesUrlPrefix(vpBase) {
  if (!vpBase || vpBase === '/') return '/slides'
  return `${String(vpBase).replace(/\/+$/, '')}/slides`
}

/** Requêtes que le middleware ne doit pas confondre avec la SPA Slidev (sinon HTML → erreur MIME sur les modules). */
function isViteOrSourceLikeRequest(rawUrl) {
  let u
  try {
    u = new URL(rawUrl, 'http://vitepress.local')
  } catch {
    return false
  }
  const q = u.searchParams
  if (q.has('import') || q.has('raw') || q.has('url') || q.has('worker') || q.has('sharedworker')) {
    return true
  }
  const p = u.pathname
  return /\.(md|mdx|vue|ts|mts|cts|tsx|jsx)($|\?)/i.test(p)
}

/**
 * Après échec sirv : ne pas laisser VitePress répondre en HTML pour des scripts / modules.
 * Pour une navigation document, servir le index.html du deck (router Slidev en history).
 */
function send404(res) {
  res.statusCode = 404
  res.setHeader('Content-Type', 'text/plain; charset=utf-8')
  res.end('Not found')
}

function wantsAssetNotHtml(req) {
  const dest = req.headers['sec-fetch-dest']
  if (dest === 'script' || dest === 'style' || dest === 'image' || dest === 'font') return true
  const accept = req.headers.accept || ''
  if (accept.includes('text/javascript') || accept.includes('application/javascript')) return true
  return false
}

/** Racine du deck Slidev (`/` ou `/index.html`) : le routeur attend `/1` pour la première planche. */
function isSlideDeckEntrySubpath(sub) {
  const n = sub.replace(/\/+$/, '') || '/'
  return n === '/' || n === '/index.html'
}

export function vitePluginSlideDists({ base: vpBase }) {
  const prefix = slidesUrlPrefix(vpBase)
  const escaped = prefix.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
  const re = new RegExp(`^${escaped}\\/([^/]+)(.*)$`)
  /** @type {Map<string, ReturnType<typeof sirv>>} */
  const sirvBySlug = new Map()
  /** @type {Map<string, string>} */
  const indexHtmlBySlug = new Map()
  const warnedMissing = new Set()

  return {
    name: 'talks-slide-dists',
    enforce: 'pre',
    apply: 'serve',
    configureServer(server) {
      server.middlewares.use((req, res, next) => {
        const raw = req.originalUrl || req.url || '/'
        const pathPart = raw.split('?')[0]
        const m = pathPart.match(re)
        if (!m) return next()
        const slug = m[1]
        const subRaw = m[2] || '/'
        if (!listPresentationSlugs(repoRoot).includes(slug)) return next()

        const distDir = path.join(repoRoot, `dist-${slug}`)
        if (!fs.existsSync(path.join(distDir, 'index.html'))) {
          if (!warnedMissing.has(slug)) {
            warnedMissing.add(slug)
            server.config.logger.warn(
              `[talks-slide-dists] dist-${slug}/ manquant ou sans index.html — exécutez « make run » ou « npm run build » puis réessayez.`,
            )
          }
          return next()
        }

        const sub = subRaw.startsWith('/') ? subRaw : `/${subRaw}`
        const query = raw.includes('?') ? `?${raw.split('?')[1]}` : ''

        if (
          (req.method === 'GET' || req.method === 'HEAD') &&
          isSlideDeckEntrySubpath(sub) &&
          !isViteOrSourceLikeRequest(raw)
        ) {
          res.statusCode = 302
          res.setHeader('Location', `${prefix}/${slug}/1${query}`)
          res.end()
          return
        }

        if (isViteOrSourceLikeRequest(raw)) {
          return send404(res)
        }

        const origUrl = req.url
        delete req._parsedUrl
        req.url = sub + query

        let handler = sirvBySlug.get(slug)
        if (!handler) {
          handler = sirv(distDir, { dev: true, etag: true, maxAge: 0 })
          sirvBySlug.set(slug, handler)
        }

        handler(req, res, () => {
          req.url = origUrl
          delete req._parsedUrl

          if (isViteOrSourceLikeRequest(raw)) {
            return send404(res)
          }
          if (wantsAssetNotHtml(req)) {
            return send404(res)
          }
          if (req.method === 'GET') {
            let html = indexHtmlBySlug.get(slug)
            if (html === undefined) {
              const p = path.join(distDir, 'index.html')
              html = fs.readFileSync(p, 'utf8')
              indexHtmlBySlug.set(slug, html)
            }
            res.statusCode = 200
            res.setHeader('Content-Type', 'text/html; charset=utf-8')
            res.end(html)
            return
          }
          next()
        })
      })
    },
  }
}