using System.Security.Cryptography;
using QuestPDF.Drawing;

namespace LehrerApp.Templating;

/// <summary>
/// Registers application-supplied TTF/OTF font bytes for TEXT and drawing commands without
/// exposing QuestPDF types to the calling application.
/// </summary>
public static class DrawingFontRegistry
{
    private static readonly object Gate = new();
    private static readonly HashSet<string> Registered = new(StringComparer.Ordinal);

    public static void RegisterFont(string familyName, byte[] fontData)
    {
        if (string.IsNullOrWhiteSpace(familyName) || familyName.Length > 80)
            throw new ArgumentException("Der Schriftname fehlt oder ist zu lang.", nameof(familyName));
        if (fontData.Length is 0 or > 20 * 1024 * 1024)
            throw new ArgumentException("Eine Schriftdatei muss zwischen 1 Byte und 20 MB groß sein.", nameof(fontData));
        var key = familyName + ":" + Convert.ToHexString(SHA256.HashData(fontData));
        lock (Gate)
        {
            if (!Registered.Add(key)) return;
            using var stream = new MemoryStream(fontData, writable: false);
            FontManager.RegisterFontWithCustomName(familyName, stream);
        }
    }
}