using System;
using System.Text.RegularExpressions;

namespace ytLive.Services;

/// <summary>
/// TASK 32·3 — naming the broadcast that resumes a dropped show. A resumed stream is a NEW broadcast
/// with a new VOD (YouTube cannot resume a completed one), so the title has to say so; otherwise the
/// channel grows two identically named videos and the creator has to explain it.
/// <para>Pure, because the interesting cases are the boring ones: a title already marked, a second drop
/// in the same session, and YouTube's 100-character limit.</para>
/// </summary>
public static class BroadcastTitle
{
    public const int MaxLength = 100;

    private static readonly Regex ResumeMarker =
        new(@"\s*\(resumed(?: \d+)?\)\s*$", RegexOptions.IgnoreCase | RegexOptions.Compiled);

    /// <summary>The title for resume number <paramref name="resumeCount"/> (1 = first re-air).
    /// Any existing marker is replaced rather than stacked, and the base is truncated so the whole
    /// title fits YouTube's limit.</summary>
    public static string ForResume(string? title, int resumeCount)
    {
        var baseTitle = ResumeMarker.Replace(title ?? string.Empty, string.Empty).Trim();
        if (baseTitle.Length == 0) baseTitle = "LlamaCasty";

        var marker = resumeCount <= 1 ? " (resumed)" : $" (resumed {Math.Max(2, resumeCount)})";
        var room = MaxLength - marker.Length;
        if (baseTitle.Length > room) baseTitle = baseTitle[..room].TrimEnd();
        return baseTitle + marker;
    }
}