using Microsoft.Xna.Framework;
using MrGameEng.Graphics;

namespace MrGameEng.Tilemaps;

/// <summary>One tile kind: a texture region plus a tint multiplier.</summary>
/// <param name="Region">Texture region the tile is drawn with.</param>
/// <param name="Color">Tint, multiplied with the texture. White = unmodified.</param>
public readonly record struct TileDef(Texture2DRegion Region, Color Color)
{
    /// <summary>Creates an untinted tile.</summary>
    public TileDef(Texture2DRegion region)
        : this(region, Color.White)
    {
    }
}

/// <summary>
/// Maps tile ids to <see cref="TileDef"/>s. Built in code: every <see cref="Add"/> returns
/// the id to store in a <see cref="TileGrid"/>. Id 0 is reserved for "empty" (nothing drawn).
/// </summary>
public sealed class TileSet
{
    private readonly List<TileDef> _tiles = [default];

    /// <summary>Number of defined tiles including the reserved empty tile 0.</summary>
    public int Count => _tiles.Count;

    /// <summary>The tile definition for <paramref name="id"/>. Id 0 has no region.</summary>
    public TileDef this[int id] => _tiles[id];

    /// <summary>Defines a tile and returns its id (1, 2, …).</summary>
    public ushort Add(Texture2DRegion region, Color? color = null)
    {
        ArgumentNullException.ThrowIfNull(region);
        if (_tiles.Count > ushort.MaxValue)
        {
            throw new InvalidOperationException("A TileSet holds at most 65535 tiles.");
        }

        _tiles.Add(new TileDef(region, color ?? Color.White));
        return (ushort)(_tiles.Count - 1);
    }
}