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

public class SimpleAtlasPacker : EditorWindow
{
    private DefaultAsset spritesFolder;
    private int cellSize = 64;
    private int columns = 4;
    private int padding = 2;
    private string atlasName = "Buttons_Atlas";

    [MenuItem("Tools/Simple Atlas Packer")]
    public static void ShowWindow()
    {
        GetWindow(typeof(SimpleAtlasPacker));
    }

    void OnGUI()
    {
        GUILayout.Label("Simple Atlas Packer", EditorStyles.boldLabel);
        spritesFolder = (DefaultAsset)EditorGUILayout.ObjectField("Sprites Folder", spritesFolder, typeof(DefaultAsset), false);
        cellSize = EditorGUILayout.IntField("Cell Size", cellSize);
        columns = EditorGUILayout.IntField("Columns", columns);
        padding = EditorGUILayout.IntField("Padding", padding);
        atlasName = EditorGUILayout.TextField("Atlas Name", atlasName);

        if (GUILayout.Button("Generate Atlas"))
        {
            if (spritesFolder != null)
            {
                string folderPath = AssetDatabase.GetAssetPath(spritesFolder);
                GenerateAtlas(folderPath);
            }
            else
            {
                Debug.LogWarning("Please select a folder with sprites!");
            }
        }
    }

    void GenerateAtlas(string folderPath)
    {
        string[] guids = AssetDatabase.FindAssets("t:Texture2D", new[] { folderPath });
        List<Texture2D> textures = new List<Texture2D>();

        foreach (string guid in guids)
        {
            string assetPath = AssetDatabase.GUIDToAssetPath(guid);
            Texture2D tex = AssetDatabase.LoadAssetAtPath<Texture2D>(assetPath);
            if (tex != null) textures.Add(tex);
        }

        if (textures.Count == 0)
        {
            Debug.LogWarning("No textures found in folder!");
            return;
        }

        int rows = Mathf.CeilToInt((float)textures.Count / columns);
        int width = columns * (cellSize + padding) - padding;
        int height = rows * (cellSize + padding) - padding;

        Texture2D atlas = new Texture2D(width, height, TextureFormat.RGBA32, false);

        Color32[] fillColor = new Color32[width * height];
        for (int i = 0; i < fillColor.Length; i++) fillColor[i] = new Color32(0, 0, 0, 0);
        atlas.SetPixels32(fillColor);

        Dictionary<string, Dictionary<string, int>> jsonFrames = new Dictionary<string, Dictionary<string, int>>();

        for (int i = 0; i < textures.Count; i++)
        {
            int col = i % columns;
            int row = i / columns;
            int x = col * (cellSize + padding);
            int y = height - (row + 1) * (cellSize + padding) + padding;

            Texture2D tex = textures[i];
            Texture2D resized = ResizeTexture(tex, cellSize, cellSize);

            atlas.SetPixels(x, y, cellSize, cellSize, resized.GetPixels());

            var frame = new Dictionary<string, int>
            {
                {"x", x},
                {"y", y},
                {"w", cellSize},
                {"h", cellSize}
            };
            jsonFrames[Path.GetFileName(AssetDatabase.GetAssetPath(textures[i]))] = new Dictionary<string, int>(frame);
        }

        atlas.Apply();

        // Save Atlas PNG
        byte[] pngData = atlas.EncodeToPNG();
        string atlasPath = $"Assets/{atlasName}.png";
        File.WriteAllBytes(atlasPath, pngData);
        AssetDatabase.Refresh();

        // Save JSON
        string json = "{\n  \"frames\": {\n";
        int count = 0;
        foreach (var kv in jsonFrames)
        {
            json += $"    \"{kv.Key}\": {{ \"frame\": {{\"x\":{kv.Value["x"]},\"y\":{kv.Value["y"]},\"w\":{kv.Value["w"]},\"h\":{kv.Value["h"]}}} }}";
            count++;
            if (count < jsonFrames.Count) json += ",\n"; else json += "\n";
        }
        json += "  },\n  \"meta\": { \"app\": \"SimpleAtlasPacker\" }\n}";

        File.WriteAllText($"Assets/{atlasName}.json", json);
        AssetDatabase.Refresh();

        // Set sprite import settings
        TextureImporter importer = (TextureImporter)TextureImporter.GetAtPath(atlasPath);
        importer.textureType = TextureImporterType.Sprite;
        importer.spriteImportMode = SpriteImportMode.Multiple;
        importer.SaveAndReimport();

        Debug.Log(" Atlas and JSON generated!");
    }

    Texture2D ResizeTexture(Texture2D source, int width, int height)
    {
        RenderTexture rt = RenderTexture.GetTemporary(width, height);
        Graphics.Blit(source, rt);
        RenderTexture.active = rt;
        Texture2D result = new Texture2D(width, height);
        result.ReadPixels(new Rect(0, 0, width, height), 0, 0);
        result.Apply();
        RenderTexture.active = null;
        RenderTexture.ReleaseTemporary(rt);
        return result;
    }
}