using OpenTK.Mathematics;
using System.Collections.Generic;

namespace Voxel
{
    public class World
    {
        private Dictionary<(int, int), Chunk> _chunks;

        public World()
        {
            _chunks = new Dictionary<(int, int), Chunk>();
        }

        public Chunk GetChunk(int chunkX, int chunkZ)
        {
            _chunks.TryGetValue((chunkX, chunkZ), out Chunk chunk);
            return chunk;
        }

        public void AddChunk(Chunk chunk)
        {
            _chunks[(chunk.X, chunk.Y)] = chunk;
        }

        public void RemoveChunk(int chunkX, int chunkZ)
        {
            _chunks.Remove((chunkX, chunkZ));
        }

        public IEnumerable<Chunk> GetAllChunks()
        {
            return _chunks.Values;
        }

        public Blocks GetBlock(int worldX, int worldY, int worldZ)
        {
            int chunkX = worldX / Chunk.Size;
            int chunkZ = worldZ / Chunk.Size;
            Chunk chunk = GetChunk(chunkX, chunkZ);
            if (chunk == null) return 0; // air if chunk not loaded

            int localX = worldX % Chunk.Size;
            int localZ = worldZ % Chunk.Size;

            return chunk.GetBlock(localX, worldY, localZ);
        }

        public void SetBlock(int worldX, int worldY, int worldZ, Blocks block)
        {
            int chunkX = worldX / Chunk.Size;
            int chunkZ = worldZ / Chunk.Size;
            Chunk chunk = GetChunk(chunkX, chunkZ);
            if (chunk == null) return;

            int localX = worldX % Chunk.Size;
            int localZ = worldZ % Chunk.Size;

            chunk.SetBlock(localX, worldY, localZ, block);
        }

        public (bool success, Blocks block, int x, int y, int z, Vector3i normal) Raycast(Vector3 origin, Vector3 direction, float maxDistance)
        {
            int x = (int)MathF.Floor(origin.X);
            int y = (int)MathF.Floor(origin.Y);
            int z = (int)MathF.Floor(origin.Z);

            int stepX = direction.X > 0 ? 1 : -1;
            int stepY = direction.Y > 0 ? 1 : -1;
            int stepZ = direction.Z > 0 ? 1 : -1;

            float tDeltaX = direction.X != 0 ? MathF.Abs(1 / direction.X) : float.MaxValue;
            float tDeltaY = direction.Y != 0 ? MathF.Abs(1 / direction.Y) : float.MaxValue;
            float tDeltaZ = direction.Z != 0 ? MathF.Abs(1 / direction.Z) : float.MaxValue;

            float tMaxX = direction.X > 0
                ? (MathF.Ceiling(origin.X) - origin.X) * tDeltaX
                : (origin.X - MathF.Floor(origin.X)) * tDeltaX;
            float tMaxY = direction.Y > 0
                ? (MathF.Ceiling(origin.Y) + 1 - origin.Y) * tDeltaY
                : (origin.Y - MathF.Floor(origin.Y)) * tDeltaY;
            float tMaxZ = direction.Z > 0
                ? (MathF.Ceiling(origin.Z) + 1 - origin.Z) * tDeltaZ
                : (origin.Z - MathF.Floor(origin.Z)) * tDeltaZ;

            float distance = 0f;
            Vector3i normal = Vector3i.Zero;

            while (distance <= maxDistance)
            {
                Blocks block = GetBlock(x, y, z);
                if (block != Blocks.Air)
                {
                    return (true, block, x, y, z, normal);
                }

                // step to next voxel
                if (tMaxX < tMaxY && tMaxX < tMaxZ)
                {
                    x += stepX;
                    distance = tMaxX;
                    tMaxX += tDeltaX;
                    normal = new Vector3i(stepX > 0 ? -1 : 1, 0, 0);
                }
                else if (tMaxY < tMaxZ)
                {
                    y += stepY;
                    distance = tMaxY;
                    tMaxY += tDeltaY;
                    normal = new Vector3i(0, stepY > 0 ? -1 : 1, 0);
                }
                else
                {
                    z += stepZ;
                    distance = tMaxZ;
                    tMaxZ += tDeltaZ;
                    normal = new Vector3i(0, 0, stepZ > 0 ? -1 : 1);
                }
            }

            return (false, Blocks.Air, 0, 0, 0, normal);
        }

        public void Update()
        {

        }
    }
}