/**
 * Embed providers (D-05). Stored posts hold only the placeholder
 * <figure data-embed="PROVIDER" data-id="ID"></figure>; the layer turns it
 * into the real iframe. Adding a provider is one entry here and one in the
 * layer's table.
 */
export interface EmbedProvider {
  /** The name shown on the editor card. */
  name: string
  /** The id the placeholder may hold. */
  idPattern: RegExp
  /** Returns the id from a provider URL, or null. */
  idFromUrl: (url: URL) => string | null
}

const YOUTUBE_HOSTS = new Set(['youtube.com', 'www.youtube.com', 'm.youtube.com', 'music.youtube.com', 'youtube-nocookie.com', 'www.youtube-nocookie.com'])

export const EMBED_PROVIDERS = {
  youtube: {
    name: 'YouTube',
    idPattern: /^[A-Za-z0-9_-]{11}$/,
    idFromUrl(url: URL): string | null {
      const host = url.hostname.toLowerCase()
      if (host === 'youtu.be') {
        return url.pathname.split('/')[1] ?? null
      }
      if (!YOUTUBE_HOSTS.has(host)) return null
      if (url.pathname === '/watch') return url.searchParams.get('v')
      const match = /^\/(?:shorts|embed)\/([^/]+)\/?$/.exec(url.pathname)
      return match ? match[1]! : null
    },
  },
} as const satisfies Record<string, EmbedProvider>

export type EmbedProviderName = keyof typeof EMBED_PROVIDERS

export function isEmbedProvider(name: string): name is EmbedProviderName {
  return Object.prototype.hasOwnProperty.call(EMBED_PROVIDERS, name)
}

/**
 * parseEmbedUrl returns the provider and id for a supported video URL
 * (youtube.com/watch?v=, youtu.be/, youtube.com/shorts/ and
 * youtube.com/embed/ for YouTube), or null for anything else.
 */
export function parseEmbedUrl(input: string): { provider: EmbedProviderName; id: string } | null {
  let url: URL
  try {
    url = new URL(input.trim())
  } catch {
    return null
  }
  if (url.protocol !== 'https:' && url.protocol !== 'http:') return null
  for (const provider of Object.keys(EMBED_PROVIDERS) as EmbedProviderName[]) {
    const id = EMBED_PROVIDERS[provider].idFromUrl(url)
    if (id && EMBED_PROVIDERS[provider].idPattern.test(id)) return { provider, id }
  }
  return null
}