using OpenTK.Graphics.OpenGL4;

namespace VoxelEngine.Rendering;

public sealed class ChunkRenderer : World.Streaming.IChunkRenderer
{
    private const int FloatsPerVertex = 6; // pos.xyz, uv, shade

    private readonly int _vao;
    private readonly int _vbo;
    private readonly int _vertexCount;

    public ChunkRenderer(float[] vertices)
    {
        this._vertexCount = vertices.Length / FloatsPerVertex;
        int stride = FloatsPerVertex * sizeof(float);

        this._vao = GL.GenVertexArray();
        GL.BindVertexArray(this._vao);

        this._vbo = GL.GenBuffer();
        GL.BindBuffer(BufferTarget.ArrayBuffer, this._vbo);
        GL.BufferData(BufferTarget.ArrayBuffer, vertices.Length * sizeof(float), vertices, BufferUsageHint.StaticDraw);

        // location 0: position (vec3) at offset 0
        GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, stride, 0);
        GL.EnableVertexAttribArray(0);

        // location 1: uv (vec2) at offset 3 floats
        GL.VertexAttribPointer(1, 2, VertexAttribPointerType.Float, false, stride, 3 * sizeof(float));
        GL.EnableVertexAttribArray(1);

        // location 2: shade (float) at offset 5 floats
        GL.VertexAttribPointer(2, 1, VertexAttribPointerType.Float, false, stride, 5 * sizeof(float));
        GL.EnableVertexAttribArray(2);

        GL.BindVertexArray(0);
    }

    public void Draw()
    {
        GL.BindVertexArray(this._vao);
        GL.DrawArrays(PrimitiveType.Triangles, 0, this._vertexCount);
        GL.BindVertexArray(0);
    }

    public void Dispose()
    {
        GL.DeleteBuffer(this._vbo);
        GL.DeleteVertexArray(this._vao);
    }
}