/* ═══════════════════════════════════════════════════════════════
   EMBEDS

   Turns the link an admin pastes into the URL an <iframe> can
   load. People paste the page they're looking at — a YouTube watch
   or live link, a Facebook video, a Vimeo page — not the embed
   form, so those are recognised and rewritten. Anything else that
   is https is assumed to already be an embed URL and passed
   through; anything that isn't https is refused, so the hero never
   frames a plain-http or javascript: URL.

   Streams start muted: browsers only autoplay muted video, and a
   hero that starts shouting is worse than one that asks.
   ═══════════════════════════════════════════════════════════════ */

function youtubeId(url: URL): string | null {
  const host = url.hostname.replace(/^www\.|^m\./, '')
  if (host === 'youtu.be') return url.pathname.slice(1) || null
  if (host !== 'youtube.com' && host !== 'youtube-nocookie.com') return null

  const v = url.searchParams.get('v')
  if (v) return v

  // /live/ID, /embed/ID, /shorts/ID
  const match = url.pathname.match(/^\/(?:live|embed|shorts)\/([\w-]+)/)
  return match?.[1] ?? null
}

/** An iframe src for a pasted stream link, or null if it can't be framed. */
export function livestreamEmbedUrl(raw?: string | null): string | null {
  if (!raw) return null

  let url: URL
  try {
    url = new URL(raw.trim())
  } catch {
    return null
  }
  if (url.protocol !== 'https:') return null

  const yt = youtubeId(url)
  if (yt) {
    return `https://www.youtube-nocookie.com/embed/${encodeURIComponent(yt)}?autoplay=1&mute=1&playsinline=1`
  }

  const host = url.hostname.replace(/^www\./, '')

  if (host === 'vimeo.com') {
    const id = url.pathname.match(/^\/(?:event\/)?(\d+)/)?.[1]
    if (id) {
      return url.pathname.startsWith('/event/')
        ? `https://vimeo.com/event/${id}/embed?autoplay=1&muted=1`
        : `https://player.vimeo.com/video/${id}?autoplay=1&muted=1`
    }
  }

  if ((host === 'facebook.com' || host === 'fb.watch') && !url.pathname.startsWith('/plugins/')) {
    return `https://www.facebook.com/plugins/video.php?href=${encodeURIComponent(url.href)}&autoplay=1&mute=1`
  }

  return url.href
}