using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using UnityEditor;
using UnityEngine;
/// <summary>
/// 将未完全使用4张贴图的T4M材质裁剪到低消耗版本
/// </summary>
public class T4MMaterialTrim
{
    [MenuItem("ResourceTool/Fix T4M Material")]
    public static void TrimT4MMaterial()
    {
        var materialPath = (from assetPath in AssetDatabase.GetAllAssetPaths()
            let extension = Path.GetExtension(assetPath)
            where extension != null && extension.Equals(".mat", StringComparison.OrdinalIgnoreCase)
            select assetPath).ToArray();
        var instance = new T4MMaterialTrim(materialPath);
        instance.Start();
    }

    private readonly string[] _materialPaths;
    private Shader[] _t4MCommon;
    private Shader[] _t4MBump;
    private int _index;
    private T4MMaterialTrim(string[] materialPaths)
    {
        _materialPaths = materialPaths;
    }

    private void Start()
    {
        var error = false;
        _index = 0;
        _t4MCommon = new Shader[3];
        if (!AddShader(_t4MCommon, 0, "Zhanyou/Scene/T2M 2 Textures"))
            error = true;
        if (!AddShader(_t4MCommon, 1, "Zhanyou/Scene/T3M 3 Textures"))
            error = true;
        if (!AddShader(_t4MCommon, 2, "Zhanyou/Scene/T4M 4 Textures"))
            error = true;
        
        _t4MBump = new Shader[3];
        if (!AddShader(_t4MBump, 0, "Zhanyou/Scene/T2M 2 Textures Bump"))
            error = true;
        if (!AddShader(_t4MBump, 1, "Zhanyou/Scene/T3M 3 Textures Bump"))
            error = true;
        if (!AddShader(_t4MBump, 2, "Zhanyou/Scene/T4M 4 Textures Bump"))
            error = true;
        
        if (!error)
            EditorApplication.update = OnEditorUpdate;
    }

    private bool AddShader(IList<Shader> array, int i, string shaderName)
    {
        var shader = Shader.Find(shaderName);
        if (shader == null)
            Debug.LogError("无法获得对应Shader " + shaderName);
        else
            array[i] = shader;
        return array[i] != null;
    }

    private void OnEditorUpdate()
    {
        try
        {
            if (_index < _materialPaths.Length)
            {
                var path = _materialPaths[_index];
                var material = AssetDatabase.LoadAssetAtPath<Material>(path);
                if (material != null && material.shader != null)
                {
                    if (_t4MCommon.Contain(material.shader))
                    {
                        var level = GetShaderLevel(material, _t4MCommon);
                        var newLevel = GetFixedShaderLevel(material, level);
                        if (newLevel >= 0 && newLevel < level)
                        {
                            material.shader = _t4MCommon[newLevel];
                            EditorUtility.SetDirty(material);
                            Debug.LogWarning(string.Format("T4M材质 {0}由{1}降低至{2}！", path, level + 2, newLevel + 2));
                        }
                    }
                    else if (_t4MBump.Contain(material.shader))
                    {
                        var level = GetShaderLevel(material, _t4MBump);
                        var newLevel = GetFixedShaderLevel(material, level);
                        if (newLevel >= 0 && newLevel < level)
                        {
                            for(var i = newLevel; i < level; i++)
                            {
                                var bumpName = "_BumpSplat" + (i + 2);
                                material.SetTexture(bumpName, null);
                            }
                            material.shader = _t4MBump[newLevel];
                            EditorUtility.SetDirty(material);
                            Debug.LogWarning(string.Format("T4M法线材质 {0}由{1}降低至{2}！", path, level + 2, newLevel + 2));
                        }
                    }
                }
                _index++;
                Debug.Log(string.Format("完成检查{0} / {1}", _index, _materialPaths.Length));
            }
            else
            {
                EditorApplication.update = null;
                AssetDatabase.SaveAssets();
                AssetDatabase.Refresh();
            }
        }
        catch (Exception e)
        {
            EditorApplication.update = null;
            Debug.LogError(e.ToString());
        }
    }

    private int GetShaderLevel(Material material, IList<Shader> array)
    {
        return array.IndexOf(material.shader);
    }
    
    private int GetFixedShaderLevel(Material material, int level)
    {
        var error = false;
        var lastNull = true;
        var textureCount = 0;
        for (var i = level + 1; i >= 0; i--)
        {
            var colorName = "_Splat" + i;
            var texture = material.GetTexture(colorName);
            if (texture != null)
                textureCount++;
            else if (!lastNull)
            {
                error = true;
                break;
            }

            lastNull = texture == null;
        }

        if (error)
        {
            Debug.LogError(string.Format("材质{0}中间有贴图缺失！", AssetDatabase.GetAssetPath(material)));
            textureCount = 0;
        }
        else if (textureCount < 2)
            Debug.LogError(string.Format("材质{0}的有效贴图数目只有{1}", AssetDatabase.GetAssetPath(material), textureCount));
        return textureCount - 2;
    }
}