// Streaming-media detection, background half. docs/05 §3: sniff `.m3u8`/`.mpd` and the
// HLS/DASH content types on the wire, then tell the tab's content script a manifest was
// seen. The extension never parses the manifest itself — media.listVariants (daemon-side)
// does that; this module only recognizes "this response is probably a manifest".

const MANIFEST_EXTENSIONS = ['.m3u8', '.mpd'];
const MANIFEST_CONTENT_TYPES = [
  'application/vnd.apple.mpegurl',
  'application/x-mpegurl',
  'audio/mpegurl',
  'application/dash+xml',
];

/** Extension check ignores the query string — `manifest.m3u8?token=…` still counts. */
export function isManifestUrl(url: string): boolean {
  let pathname: string;
  try {
    pathname = new URL(url).pathname.toLowerCase();
  } catch {
    return false;
  }
  return MANIFEST_EXTENSIONS.some((ext) => pathname.endsWith(ext));
}

export function isManifestContentType(contentType: string | null | undefined): boolean {
  if (!contentType) return false;
  const base = contentType.split(';')[0]!.trim().toLowerCase();
  return MANIFEST_CONTENT_TYPES.includes(base);
}

export function looksLikeManifest(url: string, contentType: string | null | undefined): boolean {
  return isManifestUrl(url) || isManifestContentType(contentType);
}

export interface DetectedManifest {
  tabId: number;
  url: string;
  headers: Array<{ name: string; value: string }>;
}

interface HeadersReceivedDetails {
  tabId: number;
  url: string;
  responseHeaders?: Array<{ name: string; value: string }>;
}

export interface MediaWebRequest {
  onHeadersReceived: {
    addListener(
      cb: (details: HeadersReceivedDetails) => void,
      filter: { urls: string[]; types?: string[] },
      extraInfoSpec?: string[],
    ): void;
  };
}

/**
 * Watches responses for HLS/DASH manifests and reports each hit once per (tab, url) —
 * a page can request the same manifest repeatedly (HLS live-refresh) and the content
 * script only needs to hear about it once to show the panel.
 */
export class MediaWatcher {
  private readonly seen = new Set<string>();

  constructor(private readonly onDetected: (m: DetectedManifest) => void) {}

  attach(webRequest: MediaWebRequest): void {
    webRequest.onHeadersReceived.addListener(
      (details) => this.handle(details),
      { urls: ['<all_urls>'] },
      ['responseHeaders'],
    );
  }

  private handle(details: HeadersReceivedDetails): void {
    if (details.tabId < 0) return; // not a request associated with any tab
    const headers = details.responseHeaders ?? [];
    const contentType = headers.find((h) => h.name.toLowerCase() === 'content-type')?.value;
    if (!looksLikeManifest(details.url, contentType)) return;

    const key = `${details.tabId}:${details.url}`;
    if (this.seen.has(key)) return;
    this.seen.add(key);

    this.onDetected({ tabId: details.tabId, url: details.url, headers });
  }
}