using System;
using System.Collections.Generic;
using System.IO;
using UnityEditor;
using UnityEngine;
using Object = UnityEngine.Object;

namespace Editor {
    public class AtlasPacker : EditorWindow {
        private int _blockSize = 16;
        private int _atlasSizeInBlocks = 16;
        private int _atlasSize;
        
        private Object[] _rawTextures = new Object[256];
        private List<Texture2D> _sortedTextures = new List<Texture2D>();
        private Texture2D _atlas;

        [MenuItem("Minecraft/Atlas Packer")]
        private static void ShowWindow() {
            var window = GetWindow<AtlasPacker>();
            window.titleContent = new GUIContent("Atlas Packer");
            window.Show();
        }

        private void OnGUI() {
            _atlasSize = _blockSize * _atlasSizeInBlocks;
            
            GUILayout.Label("Minecraft Atlas Packer", EditorStyles.boldLabel);
            
            _blockSize = EditorGUILayout.IntField("Block Size", _blockSize);
            _atlasSizeInBlocks = EditorGUILayout.IntField("Atlas Size in Blocks", _atlasSizeInBlocks);
            
            GUILayout.Label(_atlas);
            
            if (GUILayout.Button("Load Textures")) {
                LoadTextures();
                PackAtlas();
                Debug.Log("[Atlas Packer] Loaded " + _sortedTextures.Count + " textures.");
            }
            
            if (GUILayout.Button("Clear Textures")) {
                _atlas = new Texture2D(_atlasSize, _atlasSize);
                Debug.Log("[AtlasPacker] Cleared textures");
            }
            
            if (GUILayout.Button("Save Atlas")) {
                byte[] bytes = _atlas.EncodeToPNG();

                try {
                    File.WriteAllBytes(Application.dataPath + "/Textures/PackedAtlas.png", bytes);
                } catch {
                    Debug.LogError("[AtlasPacker] Failed to save atlas");
                }
            }
        }

        private void LoadTextures() {
            _sortedTextures.Clear();
            _rawTextures = Resources.LoadAll("AtlasPacker", typeof(Texture2D));
            
            int index = 0;
            foreach (var texture in _rawTextures) {
                Texture2D t = (Texture2D) texture;
                if (t.width != _blockSize || t.height != _blockSize) {
                    continue;
                }

                _sortedTextures.Add(t);
                
                index++;
            }
        }

        private void PackAtlas() {
            _atlas = new Texture2D(_atlasSize, _atlasSize);
            Color[] pixels = new Color[_atlasSize * _atlasSize];

            for (int x = 0; x < _atlasSize; x++) {
                for (int y = 0; y < _atlasSize; y++) {
                    int currentBlockX = x / _blockSize;
                    int currentBlockY = y / _blockSize;

                    int index = currentBlockY * _atlasSizeInBlocks + currentBlockX;
                    
                    if (index >= _sortedTextures.Count) {
                        pixels[(_atlasSize - y - 1) * _atlasSize + x] = Color.clear;
                        continue;
                    }
                    
                    Texture2D texture = _sortedTextures[index];
                    pixels[(_atlasSize - y - 1) * _atlasSize + x] = texture.GetPixel(x, _blockSize - y - 1);
                }
            }
            
            _atlas.SetPixels(pixels);
            _atlas.Apply();
        }
    }
}