export const loadYouTubeIframeApi = (): Promise<typeof window.YT> => {
  return new Promise((resolve, reject) => {
    if (window.YT && window.YT.Player) {
      resolve(window.YT);
      return;
    }

    const existingScript = document.getElementById('youtube-iframe-api');
    
    const checkReady = () => {
      if (window.YT && window.YT.Player) {
        resolve(window.YT);
      } else {
        // API script might be loaded but YT object not yet initialized
        // This can happen if onYouTubeIframeAPIReady hasn't fired or was missed.
        // We poll briefly.
        let attempts = 0;
        const interval = setInterval(() => {
          attempts++;
          if (window.YT && window.YT.Player) {
            clearInterval(interval);
            resolve(window.YT);
          } else if (attempts > 20) { // Try for ~2 seconds
            clearInterval(interval);
            reject(new Error('YouTube Iframe API loaded but YT object not found after timeout.'));
          }
        }, 100);
      }
    };

    if (existingScript) {
      // If script tag exists, it might be loading or loaded.
      if (window.YT && window.YT.Player) {
         resolve(window.YT);
         return;
      }
      // Cast to access readyState, which might not be in default TS lib HTMLScriptElement
      const scriptElement = existingScript as HTMLScriptElement & { readyState?: string };
      if (scriptElement.readyState === 'loaded' || scriptElement.readyState === 'complete') {
        checkReady();
      } else {
        existingScript.addEventListener('load', checkReady);
        existingScript.addEventListener('error', () => reject(new Error('Failed to load existing YouTube API script.')));
      }
      return;
    }

    const tag = document.createElement('script');
    tag.id = 'youtube-iframe-api';
    tag.src = 'https://www.youtube.com/iframe_api';
    const firstScriptTag = document.getElementsByTagName('script')[0];
    if (firstScriptTag && firstScriptTag.parentNode) {
      firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);
    } else {
      // Fallback if no script tags exist (unlikely for a working app)
      document.head.appendChild(tag);
    }

    (window as any).onYouTubeIframeAPIReady = () => {
       if (window.YT && window.YT.Player) {
        resolve(window.YT);
      } else {
        // This case should ideally not happen if API is working correctly
        reject(new Error('onYouTubeIframeAPIReady fired but YT.Player not found.'));
      }
    };

    tag.addEventListener('error', (e) => {
      // Use a more generic error message or inspect 'e' for details if needed
      reject(new Error('Failed to load YouTube Iframe API script.'));
    });
  });
};