using System;
using System.IO;
using PhxhSDK;
using UnityEditor;
using UnityEngine;
using Object = UnityEngine.Object;

public class SplitTextureUtil
{
    [MenuItem("Assets/*Custom/贴图/切图")]
    public static void SplitTexture()
    {
        var texture = Selection.activeObject as Texture2D;
        if (texture)
        {
            var path = AssetDatabase.GetAssetPath(texture);
            var dir = Path.GetDirectoryName(path).Replace("\\", "/");
            SplitTexture(texture, 1024, 1024, dir, "");
        }
    }

    /// <summary>
    /// 分割贴图
    /// </summary>
    /// <param name="texture">要分割的贴图</param>
    /// <param name="width">分割后的块的宽度(像素)</param>
    /// <param name="height">分割后的块的高度(像素)</param>
    /// <param name="directory">分割后贴图的位置</param>
    /// <param name="prefix">文件名前缀(可选)</param>
    public static Texture2D[,] SplitTexture(Texture2D texture, int width, int height, string directory, string prefix = "")
    {
        var row = Mathf.CeilToInt(texture.height * 1f / height);
        var column = Mathf.CeilToInt(texture.width * 1f / width);
        var rowReminder = texture.height % height;
        if (rowReminder == 0)
            rowReminder = height;
        var columnReminder = texture.width % width;
        if (columnReminder == 0)
            columnReminder = width;
        
        Texture2D[,] result = new Texture2D[row, column];

        var allPixels = texture.GetPixels();
        for (int r = 0; r < row; r++)
        {
            for (int c = 0; c < column; c++)
            {
                var realWidth = c == column - 1 ? columnReminder : width;
                var realHeight = r == row - 1 ? rowReminder : height;

                var pixelCount = realWidth * realHeight;
                var textureOutput = TextureUtils.Create($"split_{texture.name}_{r}_{c}", realWidth, realHeight);
                Color[] pixels = new Color[pixelCount];
                var startIndex = r * height * texture.width + c * width;
                for (int i = 0; i < pixelCount; i++)
                {
                    var innerRow = i / realWidth;
                    var innerColumn = i % realWidth;
                    var pickIndex = startIndex + innerRow * texture.width + innerColumn;
                    pixels[i] = allPixels[pickIndex];
                }

                textureOutput.SetPixels(pixels);
                Byte[] bytes = textureOutput.EncodeToPNG();
                var path = $"{directory}/{prefix}split_{texture.name}_{r}_{c}.jpg";
                FileStream fs = File.Open(path, FileMode.Create);
                BinaryWriter writer = new BinaryWriter(fs);
                writer.Write(bytes);
                writer.Flush();
                writer.Close();
                fs.Close();
                Object.DestroyImmediate(textureOutput);
                AssetDatabase.Refresh();
                
                // 获取图片设置
                var importer = AssetImporter.GetAtPath(path) as TextureImporter;
                if (importer != null)
                {
                    importer.alphaIsTransparency = true;
                    importer.SaveAndReimport();
                }
                AssetDatabase.Refresh();
                
                result[r, c] = AssetDatabase.LoadAssetAtPath<Texture2D>(path);
            }
        }

        return result;
    }
}