using OpenTK.Graphics.OpenGL4;
using static System.Runtime.InteropServices.JavaScript.JSType;

namespace Voxel
{
    static class Renderer
    {
        private static int _ssbo;
        private static int _vao;
        private static bool _buffersDirty;

        private static Dictionary<(int, int), int> _chunkBufferSizes = new Dictionary<(int, int), int>();
        private static List<ChunkMesh> _chunkMeshes = new List<ChunkMesh>();
        private static Shader _shader;
        private static readonly Texture _texture;
        private static World? _world;

        static Renderer()
        {
            string vertexPath = "Shaders/shader.vert";
            string fragmentPath = "Shaders/shader.frag";
            string texturePath = "atlas.png";

            _shader = new Shader(vertexPath, fragmentPath);
            _texture = new Texture(texturePath);

            _shader.SetInt("uTexture", 0);

            _ssbo = GL.GenBuffer();
            _vao = GL.GenVertexArray();

            GL.BindVertexArray(_vao);
            GL.BindBuffer(BufferTarget.ShaderStorageBuffer, _ssbo);

            GL.BufferData(BufferTarget.ShaderStorageBuffer, 1024 * 1024 * 128, IntPtr.Zero, BufferUsageHint.DynamicDraw);
            GL.BindBufferBase(BufferRangeTarget.ShaderStorageBuffer, 0, _ssbo);
        }

        public static void Render()
        {
            GL.BindVertexArray(_vao);
            GL.BindBuffer(BufferTarget.ShaderStorageBuffer, _ssbo);

            _shader.Use();
            _shader.SetMatrix4("view", Camera.view);
            _shader.SetMatrix4("projection", Camera.projection);

            if (_buffersDirty)
            {
                UpdateAllChunksBuffer();
                _buffersDirty = false;
            }

            RenderWorld();
        }

        private static void UpdateAllChunksBuffer()
        {
            if (_world == null) return;

            int offset = 0;
            foreach (Chunk chunk in _world.GetAllChunks())
            {
                ChunkMesh chunkMesh = chunk.GetChunkMesh();

                if (chunkMesh.NeedsUpdate)
                {
                    byte[] data = chunkMesh.GetPackedData();
                    GL.BufferSubData(BufferTarget.ShaderStorageBuffer, (IntPtr)offset * 8, chunkMesh.Size * 8, data);
                }

                _chunkBufferSizes[(chunk.X, chunk.Y)] = offset;
                offset += chunkMesh.Size * 8;
            }
        }

        private static void RenderWorld()
        {
            if (_world == null) return;

            foreach (Chunk chunk in _world.GetAllChunks())
            {
                ChunkMesh chunkMesh = chunk.GetChunkMesh();

                if (chunkMesh.Size == 0) continue;

                if (!_chunkBufferSizes.TryGetValue((chunk.X, chunk.Y), out int offset)) continue;

                _shader.SetInt("chunkX", chunk.X);
                _shader.SetInt("chunkY", chunk.Y);

                //GL.MemoryBarrier(MemoryBarrierFlags.ShaderStorageBarrierBit);
                GL.DrawArrays(PrimitiveType.Triangles, offset * 6, chunkMesh.Size * 6);
            }
        }

        public static void SetWorld(World world)
        {
            _world = world;
            _buffersDirty = true;
        }

        public static void MarkBuffersDirty()
        {
            _buffersDirty = true;
        }
    }
}