// Transport-only lookup. Review eligibility continues to belong to the story
// and release manifests; an HTTPS URL never confers audio approval.
const manifest = require('./cosMediaManifest')
const paths = Object.create(null)
const urls = Object.create(null)
const SHARE_ASSET_ID = 'image.tang.share-preview'

for (const entry of manifest.entries) {
  paths[entry.sourcePath] = entry
  urls[entry.url] = entry
}

function entryFor(value) {
  if (typeof value !== 'string') return null
  if (urls[value]) return urls[value]
  let relative = value.replace(/^\//, '')
  if (relative.startsWith(`${manifest.namespace}/`)) {
    relative = relative.slice(manifest.namespace.length + 1)
  }
  return paths[relative] || null
}

function resolve(value) {
  const entry = entryFor(value)
  return entry ? entry.url : ''
}

function verifiedUrl(value, sha256, kind) {
  const entry = urls[value]
  return entry && entry.sha256 === sha256 && entry.kind === kind
    ? entry.url : ''
}

function mapMedia(value) {
  if (typeof value === 'string') {
    if (/^\/(?:[a-z0-9-]+\/)?(?:assets|package-[a-z0-9-]+)\/.*\.(?:jpe?g|png|webp|gif|svg|avif|mp3|wav|aac|m4a|ogg|mp4|webm|mov)$/i.test(value)) {
      // Unregistered declarations remain text-only; never guess an object URL.
      return resolve(value)
    }
    return value
  }
  if (Array.isArray(value)) return value.map(mapMedia)
  if (!value || typeof value !== 'object') return value
  const mapped = {}
  Object.keys(value).forEach(key => { mapped[key] = mapMedia(value[key]) })
  return mapped
}

function beginComicImage(page, pageData) {
  const previous = page._cosComicImage
  if (!previous || previous.pageId !== pageData.currentPageId) {
    page._cosComicImage = {
      pageId: pageData.currentPageId,
      generation: (previous ? previous.generation : 0) + 1,
      failed: Object.create(null),
      lastPatch: null,
    }
  }
  const state = page._cosComicImage
  pageData.comicImageGeneration = state.generation
  // Ordinary reader interactions re-render this page. They must not revive a
  // URL that already failed or replace terminal text fallback with an image.
  if (state.lastPatch) Object.assign(pageData, state.lastPatch)
}

function isCurrentComicImageEvent(page, event) {
  const state = page._cosComicImage
  const dataset = event && event.currentTarget && event.currentTarget.dataset
  return Boolean(state && dataset && !page.__tangDead && !page.__tangOriginalUnloaded
    && page.__tangVisible !== false && page.data.comicImageSrc
    && state.pageId === page.data.currentPageId
    && dataset.cosPageId === state.pageId
    && Number(dataset.cosImageGeneration) === state.generation
    && dataset.cosImageSrc === page.data.comicImageSrc)
}

function recordComicImageError(page, event) {
  if (!isCurrentComicImageEvent(page, event)) return false
  const state = page._cosComicImage
  const src = page.data.comicImageSrc
  if (state.failed[src]) return false
  state.failed[src] = true
  return true
}

function canUseComicFallback(page, src) {
  const state = page._cosComicImage
  const entry = entryFor(src)
  return Boolean(state && entry && entry.kind === 'image' && !state.failed[src])
}

function applyComicImageFallback(page, patch) {
  if (page._cosComicImage) page._cosComicImage.lastPatch = { ...patch }
  page.setData(patch)
}

function prepareSharePreview(page, assetManager) {
  if (page._sharePreviewPromise) return page._sharePreviewPromise
  const generation = page.__tangShowGeneration
  const alive = () => !page.__tangDead && !page.__tangOriginalUnloaded
    && page.__tangVisible !== false && page.__tangShowGeneration === generation
  // Resolve again for each share; the manager rehashes cached bytes before use.
  const promise = Promise.resolve().then(() => assetManager.resolve(SHARE_ASSET_ID))
    .then(result => {
      if (!alive()) return ''
      const localPath = result && result.available && result.uri || ''
      page.setData({ sharePreviewLocalPath: localPath })
      return localPath
    })
    .catch(() => {
      if (alive()) page.setData({ sharePreviewLocalPath: '' })
      return ''
    })
    .finally(() => {
      if (page._sharePreviewPromise === promise) page._sharePreviewPromise = null
    })
  page._sharePreviewPromise = promise
  return promise
}

module.exports = {
  SHARE_ASSET_ID, entryFor, resolve, verifiedUrl, mapMedia, prepareSharePreview,
  beginComicImage, isCurrentComicImageEvent, recordComicImageError,
  canUseComicFallback, applyComicImageFallback,
}