using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using UnityEditor;
using UnityEngine;

public class ReferenceFinderData
{
    //缓存路径
    private const string CACHE_PATH = "Library/ReferenceFinderCache";
    private const string CACHE_VERSION = "V1";
    //资源引用信息字典
    public Dictionary<string, AssetDescription> assetDict = new Dictionary<string, AssetDescription>();    

    //收集资源引用信息并更新缓存
    public void CollectDependenciesInfo()
    {
        try
        {          
            ReadFromCache();
            var allAssets = AssetDatabase.GetAllAssetPaths();
            int totalCount = allAssets.Length;
            for (int i = 0; i < allAssets.Length; i++)
            {
                //每遍历100个Asset，更新一下进度条，同时对进度条的取消操作进行处理
                if ((i % 100 == 0) && EditorUtility.DisplayCancelableProgressBar("Refresh", string.Format("Collecting {0} assets", i), (float)i / totalCount))
                {
                    EditorUtility.ClearProgressBar();
                    return;
                }
                if (File.Exists(allAssets[i]))
                    ImportAsset(allAssets[i]);
                if (i % 2000 == 0)
                    GC.Collect();
            }      
            //将信息写入缓存
            EditorUtility.DisplayCancelableProgressBar("Refresh", "Write to cache", 1f);
            WriteToChache();
            //生成引用数据
            EditorUtility.DisplayCancelableProgressBar("Refresh", "Generating asset reference info", 1f);
            UpdateReferenceInfo();
            EditorUtility.ClearProgressBar();
        }
        catch(Exception e)
        {
            Debug.LogError(e);
            EditorUtility.ClearProgressBar();
        }
    }

    //通过依赖信息更新引用信息
    private void UpdateReferenceInfo()
    {
        foreach(var asset in assetDict)
        {
            foreach(var assetGuid in asset.Value.dependencies)
            {
                assetDict[assetGuid].references.Add(asset.Key);
            }
        }
    }

    //生成并加入引用信息
    private void ImportAsset(string path)
    {
        if (!path.StartsWith("Assets/"))
            return;

        //通过path获取guid进行储存
        string guid = AssetDatabase.AssetPathToGUID(path);
        //获取该资源的最后修改时间，用于之后的修改判断
        Hash128 assetDependencyHash = AssetDatabase.GetAssetDependencyHash(path);
        //如果assetDict没包含该guid或包含了修改时间不一样则需要更新
        if (!assetDict.ContainsKey(guid) || assetDict[guid].assetDependencyHash != assetDependencyHash.ToString())
        {
            //将每个资源的直接依赖资源转化为guid进行储存
            var guids = AssetDatabase.GetDependencies(path, false).
                Select(p => AssetDatabase.AssetPathToGUID(p)).
                ToList();

            //生成asset依赖信息，被引用需要在所有的asset依赖信息生成完后才能生成
            AssetDescription ad = new AssetDescription();
            ad.name = Path.GetFileNameWithoutExtension(path);
            ad.path = path;
            ad.assetDependencyHash = assetDependencyHash.ToString();
            ad.dependencies = guids;

            if (assetDict.ContainsKey(guid))
                assetDict[guid] = ad;
            else
                assetDict.Add(guid, ad);
        }
    }

    //读取缓存信息
    public bool ReadFromCache()
    {
        assetDict.Clear();
        if (!File.Exists(CACHE_PATH))
        {
            return false;
        }

        var serializedGuid = new List<string>();
        var serializedDependencyHash = new List<string>();
        var serializedDenpendencies = new List<int[]>();
        //反序列化数据
        FileStream fs = File.OpenRead(CACHE_PATH);
        try
        {
            BinaryFormatter bf = new BinaryFormatter();
            string cacheVersion = (string) bf.Deserialize(fs);
            if (cacheVersion != CACHE_VERSION)
            {
                return false;
            }

            EditorUtility.DisplayCancelableProgressBar("Import Cache", "Reading Cache", 0);
            serializedGuid = (List<string>) bf.Deserialize(fs);
            serializedDependencyHash = (List<string>) bf.Deserialize(fs);
            serializedDenpendencies = (List<int[]>) bf.Deserialize(fs);
            EditorUtility.ClearProgressBar();
        }
        catch
        {
            //兼容旧版本序列化格式
            return false;
        }
        finally
        {
            fs.Close();
        }

        for (int i = 0; i < serializedGuid.Count; ++i)
        {
            string path = AssetDatabase.GUIDToAssetPath(serializedGuid[i]);
            if (!string.IsNullOrEmpty(path))
            {
                var ad = new AssetDescription();
                ad.name = Path.GetFileNameWithoutExtension(path);
                ad.path = path;
                ad.assetDependencyHash = serializedDependencyHash[i];
                assetDict.Add(serializedGuid[i], ad);
            }
        }

        for(int i = 0; i < serializedGuid.Count; ++i)
        {
            string guid = serializedGuid[i];
            if (assetDict.ContainsKey(guid))
            {
                var guids = serializedDenpendencies[i].
                    Select(index => serializedGuid[index]).
                    Where(g => assetDict.ContainsKey(g)).
                    ToList();
                assetDict[guid].dependencies = guids;
            }
        }
        UpdateReferenceInfo();
        return true;
    }

    //写入缓存
    private void WriteToChache()
    {
        if (File.Exists(CACHE_PATH))
            File.Delete(CACHE_PATH);

        var serializedGuid = new List<string>();
        var serializedDependencyHash = new List<string>();
        var serializedDenpendencies = new List<int[]>();
        //辅助映射字典
        var guidIndex = new Dictionary<string, int>();
        //序列化
        using (FileStream fs = File.OpenWrite(CACHE_PATH))
        {
            foreach (var pair in assetDict)
            {
                guidIndex.Add(pair.Key, guidIndex.Count);
                serializedGuid.Add(pair.Key);
                serializedDependencyHash.Add(pair.Value.assetDependencyHash);
            }

            foreach(var guid in serializedGuid)
            {
                //使用 Where 子句过滤目录
                int[] indexes = assetDict[guid].dependencies.
                    Where(s => guidIndex.ContainsKey(s)).
                    Select(s => guidIndex[s]).ToArray();
                serializedDenpendencies.Add(indexes);
            }

            BinaryFormatter bf = new BinaryFormatter();
            bf.Serialize(fs, CACHE_VERSION);
            bf.Serialize(fs, serializedGuid);
            bf.Serialize(fs, serializedDependencyHash);
            bf.Serialize(fs, serializedDenpendencies);
        }
    }
    
    //更新引用信息状态
    public void UpdateAssetState(string guid)
    {
        AssetDescription ad;
        if (assetDict.TryGetValue(guid,out ad) && ad.state != AssetState.NODATA)
        {            
            if (File.Exists(ad.path))
            {
                //修改时间与记录的不同为修改过的资源
                if (ad.assetDependencyHash != AssetDatabase.GetAssetDependencyHash(ad.path).ToString())
                {
                    ad.state = AssetState.CHANGED;
                }
                else
                {
                    //默认为普通资源
                    ad.state = AssetState.NORMAL;
                }
            }
            //不存在为丢失
            else
            {
                ad.state = AssetState.MISSING;
            }
        }
        
        //字典中没有该数据
        else if(!assetDict.TryGetValue(guid, out ad))
        {
            string path = AssetDatabase.GUIDToAssetPath(guid);
            ad = new AssetDescription();
            ad.name = Path.GetFileNameWithoutExtension(path);
            ad.path = path;
            ad.state = AssetState.NODATA;
            assetDict.Add(guid, ad);
        }
    }

    //根据引用信息状态获取状态描述
    public static string GetInfoByState(AssetState state)
    {
        if(state == AssetState.CHANGED)
        {
            return "<color=#F0672AFF>Changed</color>";
        }
        else if (state == AssetState.MISSING)
        {
            return "<color=#FF0000FF>Missing</color>";
        }
        else if(state == AssetState.NODATA)
        {
            return "<color=#FFE300FF>No Data</color>";
        }
        return "Normal";
    }

    public class AssetDescription
    {
        public string name = "";
        public string path = "";
        public string assetDependencyHash;
        public List<string> dependencies = new List<string>();
        public List<string> references = new List<string>();
        public AssetState state = AssetState.NORMAL;
    }

    public enum AssetState
    {
        NORMAL,
        CHANGED,
        MISSING,
        NODATA,        
    }
}