/**
 * Regular expression for matching YouTube video IDs in various URL formats
 */
const VIDEO_ID_REGEX = /(?:youtube\.com\/(?:[^\/]+\/.+\/|(?:v|e(?:mbed)?)\/|.*[?&]v=)|youtu\.be\/)([^"&?\/\s]{11})/i;

/**
 * Regular expression for matching standalone YouTube video IDs
 */
const SHORT_URL_REGEX = /^[a-zA-Z0-9_-]{11}$/;

/**
 * Extracts the video ID from a YouTube URL or returns the input if it's already a video ID.
 * @param {string} input - The YouTube URL or video ID
 * @returns {string|null} The extracted video ID or null if invalid
 */
export function extractVideoId(input) {
    if (!input) return null;

    // If it's already a valid video ID, return it
    if (isValidVideoId(input)) {
        return input;
    }

    // Try to extract video ID from URL
    const match = input.match(VIDEO_ID_REGEX);
    return match ? match[1] : null;
}

/**
 * Validates if the input is a valid YouTube video ID.
 * @param {string} input - The video ID to validate
 * @returns {boolean} True if the input is a valid video ID
 */
export function isValidVideoId(input) {
    if (!input) return false;
    return SHORT_URL_REGEX.test(input);
}

/**
 * Validates if the input is a valid YouTube URL or video ID.
 * @param {string} input - The URL or video ID to validate
 * @returns {boolean} True if the input is a valid YouTube URL or video ID
 */
export function isValidYouTubeUrlOrId(input) {
    if (!input) return false;

    // Check if it's a valid video ID
    if (isValidVideoId(input)) {
        return true;
    }

    // Check if it's a valid YouTube URL
    return VIDEO_ID_REGEX.test(input);
}

/**
 * Builds a YouTube embed URL from a video ID.
 * @param {string} videoId - The YouTube video ID
 * @returns {string} The YouTube embed URL
 */
export function buildEmbedUrl(videoId) {
    if (!videoId) return '';
    return `https://www.youtube.com/embed/${videoId}`;
}