using System.Collections.Generic;
using UnityEngine;

namespace Assets.Scripts {
    public class World : MonoBehaviour {
        public int seed;
        
        public Transform player;
        public Vector3 spawn;
        public BiomeAttributes biome;

        public Material material;
        public BlockType[] blockTypes;

        private readonly Chunk[,] _chunks = new Chunk[VoxelData.WorldSizeInChunks, VoxelData.WorldSizeInChunks];
        private readonly List<ChunkCoord> _activeChunks = new List<ChunkCoord>();

        private ChunkCoord _playersLastChunk;

        private void Start() {
            Random.InitState(seed);
            
            spawn = new Vector3(VoxelData.WorldSizeInBlocks / 2f, 
                                VoxelData.ChunkHeight / 2f,
                                VoxelData.WorldSizeInBlocks / 2f);
            
            GenerateWorld();
            _playersLastChunk = GetChunkCoord(player.position);
        }

        private void Update() {
            ChunkCoord playerChunk = GetChunkCoord(player.position);
            
            if (!playerChunk.Equals(_playersLastChunk)) {
                _playersLastChunk = playerChunk;
                CheckViewDistance();
            }
        }

        private void GenerateWorld() {
            for (int x = VoxelData.WorldSizeInChunks / 2 - VoxelData.ViewDistance; x < VoxelData.WorldSizeInChunks / 2 + VoxelData.ViewDistance; x++) {
                for (int z = VoxelData.WorldSizeInChunks / 2 - VoxelData.ViewDistance; z < VoxelData.WorldSizeInChunks / 2 + VoxelData.ViewDistance; z++) {
                    CreateNewChunk(x, z);
                }
            }

            player.position = spawn;
        }

        public ChunkCoord GetChunkCoord(Vector3 absPosition) {
            int x = Mathf.FloorToInt(absPosition.x / VoxelData.ChunkWidth);
            int z = Mathf.FloorToInt(absPosition.z / VoxelData.ChunkWidth);
            return new ChunkCoord(x, z);
        }

        private void CheckViewDistance() {
            ChunkCoord coord = GetChunkCoord(player.position);
            ChunkCoord[] previouslyActiveChunks = _activeChunks.ToArray();
            _activeChunks.Clear();

            for (int x = coord.x - VoxelData.ViewDistance; x < coord.x + VoxelData.ViewDistance; x++) {
                for (int z = coord.z - VoxelData.ViewDistance; z < coord.z + VoxelData.ViewDistance; z++) {
                    if (!IsChunkInWorld(new ChunkCoord(x, z))) continue;
                    Chunk chunk = _chunks[x, z];
                    
                    if (chunk == null)
                        CreateNewChunk(x, z);
                    else if (!chunk.IsActive) {
                        chunk.IsActive = true;
                    }
                    
                    _activeChunks.Add(new ChunkCoord(x, z));
                }
            }

            foreach (ChunkCoord chunk in previouslyActiveChunks) {
                if (!_activeChunks.Contains(chunk))
                    _chunks[chunk.x, chunk.z].IsActive = false;
            }
        }

        private void CreateNewChunk(int x, int z) {
            _chunks[x, z] = new Chunk(new ChunkCoord(x, z), this);
            _activeChunks.Add(new ChunkCoord(x, z));
        }

        public bool IsChunkInWorld(ChunkCoord coord) {
            return (coord.x > 0 && coord.x < VoxelData.WorldSizeInChunks - 1 &&
                    coord.z > 0 && coord.z < VoxelData.WorldSizeInChunks - 1);
        }

        public bool IsBlockInWorld(Vector3 pos) {
            return (pos.x >= 0 && pos.x < VoxelData.WorldSizeInBlocks &&
                    pos.y >= 0 && pos.y < VoxelData.ChunkHeight &&
                    pos.z >= 0 && pos.z < VoxelData.WorldSizeInBlocks);
        }

        public byte GenerateBlock(Vector3 position) {
            Vector3Int pos = new Vector3Int(Mathf.FloorToInt(position.x), 
                                            Mathf.FloorToInt(position.y),
                                            Mathf.FloorToInt(position.z));

            if (!IsBlockInWorld(position)) return 0;
            if (pos.y == 0) return 1;
            
            //Generate Block based on 2D Perlin Noise
            int terrainHeight = Mathf.FloorToInt(Noise.Get2DNoise(new Vector2(pos.x, pos.z), 0, biome.terrainScale) * biome.terrainHeight + biome.solidGroundHeight);
            int blockValue = 0;
            
            if (pos.y < terrainHeight) blockValue = 2;
            if (pos.y < terrainHeight && pos.y > terrainHeight - 4) blockValue = 5;
            if (pos.y == terrainHeight) blockValue = 3;

            if (blockValue == 2) {
                foreach (var lode in biome.lodes) {
                    if ((pos.y > lode.minHeight && pos.y < lode.maxHeight) && Noise.Get3DNoise(pos, lode.offset, lode.scale, lode.threshold))
                        blockValue = lode.blockID;
                }
            }
            
            return (byte)blockValue;
        }
    }

    [System.Serializable]
    public class BlockType {
        public string blockName;
        public bool isSolid;

        [Header("Texture Values")] 
        public int backFaceTexture;
        public int frontFaceTexture;
        public int topFaceTexture;
        public int bottomFaceTexture;
        public int leftFaceTexture;
        public int rightFaceTexture;
        
        //Back - Front - Top - Bottom - Left - Right
        public int GetTextureID(int faceIndex) {
            switch (faceIndex) {
                case 0: return backFaceTexture;
                case 1: return frontFaceTexture;
                case 2: return topFaceTexture;
                case 3: return bottomFaceTexture;
                case 4: return leftFaceTexture;
                case 5: return rightFaceTexture;
                
                default: return 0;
            }
        }
    }
}