Siteforge/server/feed-release.js

import { fetchAllEpisodes } from './routes/episodes.js'
import { loadPodcastWorkflow, laneSeasonOf } from './routes/podcast-workflow.js'

// The Spotify (Anchor) RSS feed only lists episodes that are live, so a season + episode number
// showing up there means the episode has been published. That drives two things on the public site:
//  - highlights marked "hold until released" stay hidden until their episode is in the feed
//  - study lessons with no audio of their own pick it up from the matching feed episode

const SNAPSHOT_TTL_MS = 5 * 60 * 1000

let snapshot = { items: [], at: 0 }
let inflight = null

function refreshSnapshot() {
  if (!inflight) {
    inflight = fetchAllEpisodes()
      .then(items => { snapshot = { items, at: Date.now() } })
      // Keep serving the last good copy; retry on the next TTL window
      .catch(() => { snapshot = { items: snapshot.items, at: Date.now() } })
      .finally(() => { inflight = null })
  }
  return inflight
}

async function getFeedIndex() {
  if (!snapshot.at) await refreshSnapshot()
  else if (Date.now() - snapshot.at > SNAPSHOT_TTL_MS) refreshSnapshot()

  const index = new Map()
  for (const item of snapshot.items) {
    if (item.season && /^\d+$/.test(item.episode)) index.set(`${item.season}-${item.episode}`, item)
  }
  return index
}

export function warmFeedSnapshot() {
  return refreshSnapshot()
}

// Returns a copy of the published site content with the feed applied. Run it before
// filterSiteContentByReleaseDate so audio is never added to a lesson that is still locked.
export async function applyFeedRelease(content) {
  if (!content || typeof content !== 'object' || Array.isArray(content)) return content

  const links = Array.isArray(content.podcastFeaturedLinks) ? content.podcastFeaturedLinks : []
  const studies = Array.isArray(content.studies) ? content.studies : []
  if (!links.some(l => l?.holdUntilReleased) && studies.length === 0) return content

  const [index, wf] = await Promise.all([getFeedIndex(), loadPodcastWorkflow()])
  const seasonA = laneSeasonOf('A', wf, content)
  const seasonB = laneSeasonOf('B', wf, content)

  const nextLinks = links.flatMap(link => {
    // General highlights aren't tied to a series, so there's no season to match against
    if (!link?.holdUntilReleased || link.lane === 'general') return [link]
    const season = link.lane === 'second' ? seasonB : seasonA
    const item = season && link.episodeNumber ? index.get(`${season}-${link.episodeNumber}`) : null
    if (!item) return []
    return [{ ...link, url: link.url || item.link || '' }]
  })

  const studyLane = study => {
    if (study?.lane === 'A' || study?.lane === 'B') return study.lane
    if (study?.slug && study.slug === content.seriesStudySlug) return 'A'
    if (study?.slug && study.slug === content.secondSeries?.studySlug) return 'B'
    return ''
  }

  const nextStudies = studies.map(study => {
    const lane = studyLane(study)
    const season = lane === 'A' ? seasonA : lane === 'B' ? seasonB : ''
    if (!season || !Array.isArray(study.sections)) return study
    return {
      ...study,
      sections: study.sections.map(section => {
        if (!section || section.audioEmbedUrl?.trim() || !section.episodeNumber) return section
        const item = index.get(`${season}-${String(section.episodeNumber).trim()}`)
        return item?.audioUrl ? { ...section, audioEmbedUrl: item.audioUrl } : section
      }),
    }
  })

  return { ...content, podcastFeaturedLinks: nextLinks, studies: nextStudies }
}