using System.Text.RegularExpressions;

namespace Hutopy.Infrastructure.YouTube;

public static class YouTubeUrlHelper
{
    private static readonly Regex VideoIdRegex = new(
        @"(?:youtube\.com/(?:[^/]+/.+/|(?:v|e(?:mbed)?)/|.*[?&]v=)|youtu\.be/)([^""&?/\s]{11})",
        RegexOptions.Compiled | RegexOptions.IgnoreCase);

    private static readonly Regex ShortUrlRegex = new(
        @"^[a-zA-Z0-9_-]{11}$",
        RegexOptions.Compiled);

    /// <summary>
    ///     Extracts the video ID from a YouTube URL or returns the input if it's already a video ID.
    /// </summary>
    /// <param name="input">The YouTube URL or video ID</param>
    /// <returns>The extracted video ID or null if invalid</returns>
    public static string? ExtractVideoId(string? input)
    {
        if (string.IsNullOrWhiteSpace(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
        Match match = VideoIdRegex.Match(input);
        return match.Success ? match.Groups[1].Value : null;
    }

    /// <summary>
    ///     Validates if the input is a valid YouTube video ID.
    /// </summary>
    /// <param name="input">The video ID to validate</param>
    /// <returns>True if the input is a valid video ID</returns>
    public static bool IsValidVideoId(string? input)
    {
        if (string.IsNullOrWhiteSpace(input))
        {
            return false;
        }

        return ShortUrlRegex.IsMatch(input);
    }

    /// <summary>
    ///     Validates if the input is a valid YouTube URL or video ID.
    /// </summary>
    /// <param name="input">The URL or video ID to validate</param>
    /// <returns>True if the input is a valid YouTube URL or video ID</returns>
    public static bool IsValidYouTubeUrlOrId(string? input)
    {
        if (string.IsNullOrWhiteSpace(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 VideoIdRegex.IsMatch(input);
    }
}