using System;
using System.Collections;
using System.IO;
using UnityEngine;
using UnityEngine.Networking;

namespace XGame.MiniGame
{
    // 下载并校验某小游戏版本的全部文件；产出本地目录 + 解析好的 manifest
    public sealed class MiniGameDownloader
    {
        public string LocalDir { get; private set; }
        public MiniGameManifest Manifest { get; private set; }
        public string Error { get; private set; }

        private readonly string _cdnBase; // 例如 http://.../minigame/
        private readonly string _gameId;
        private readonly int _version;

        public MiniGameDownloader(string cdnBase, string gameId, int version)
        {
            _cdnBase = NormalizeCdnBase(cdnBase);
            _gameId = gameId; _version = version;
            LocalDir = $"{Application.persistentDataPath}/minigame/{gameId}/{version}/";
        }

        private string RemoteBase => $"{_cdnBase}{_gameId}/{_version}/{MiniGamePlatform.Name}/";

        public IEnumerator Run(Action<bool> onDone)
        {
            Error = null;
            Directory.CreateDirectory(LocalDir);

            // 1) game.json（每次拉取，文件小）
            string gameJson = null;
            yield return GetText($"{RemoteBase}game.json", t => gameJson = t);
            if (gameJson == null) { Fail("下载 game.json 失败"); onDone(false); yield break; }
            try { Manifest = MiniGameManifest.ParseGameJson(gameJson); }
            catch (Exception e) { Fail("game.json 解析失败: " + e.Message); onDone(false); yield break; }
            if (Manifest.GameId != _gameId || Manifest.Version != _version)
            { Fail("game.json 与请求的 gameId/version 不符"); onDone(false); yield break; }
            if (Manifest.MinFrameworkVersion > XWorld.Framework.FrameworkInfo.Version)
            { Fail($"小游戏要求最小框架版本 {Manifest.MinFrameworkVersion}，当前框架 {XWorld.Framework.FrameworkInfo.Version}"); onDone(false); yield break; }

            // 2) files.txt（md5 清单）
            string filesTxt = null;
            yield return GetText($"{RemoteBase}files.txt", t => filesTxt = t);
            if (filesTxt == null) { Fail("下载 files.txt 失败"); onDone(false); yield break; }
            Manifest.LoadFilesList(filesTxt);

            // 验签（设计 §7）：下载 files.txt.sig，校验清单签名后才信任 md5 列表
            byte[] sig = null;
            yield return GetBytes($"{RemoteBase}files.txt.sig", b => sig = b);
            if (ClientManifestVerifier.IsConfigured)
            {
                if (sig == null) { Fail("缺少签名文件 files.txt.sig"); onDone(false); yield break; }
                if (!ClientManifestVerifier.Verify(Manifest.Digest(), sig))
                { Fail("清单签名验证失败，拒绝加载"); onDone(false); yield break; }
            }

            // 3) 按清单逐个增量下载（md5 命名；本地已存在且 md5 匹配则跳过）
            foreach (var kv in Manifest.Files)
            {
                string name = kv.Key; string md5 = kv.Value.Md5;
                string localPath = LocalDir + name;
                if (File.Exists(localPath) && Md5OfFile(localPath) == md5) continue;

                string remote = $"{RemoteBase}{Md5Name(name, md5)}";
                byte[] data = null;
                yield return GetBytes(remote, b => data = b);
                if (data == null) { Fail("下载失败: " + remote); onDone(false); yield break; }
                if (Md5OfBytes(data) != md5) { Fail("md5 不符: " + name); onDone(false); yield break; }
                Directory.CreateDirectory(Path.GetDirectoryName(localPath));
                File.WriteAllBytes(localPath, data);
            }

            onDone(true);
        }

        private void Fail(string msg) { Error = msg; Debug.LogError("[MiniGameDownloader] " + msg); }

        private static string NormalizeCdnBase(string cdnBase)
        {
            string url = string.IsNullOrWhiteSpace(cdnBase) ? "http://127.0.0.1:15081/" : cdnBase.Trim();
            if (url.StartsWith("http://file://", StringComparison.OrdinalIgnoreCase))
            {
                url = url.Substring("http://".Length);
            }
            else if (url.StartsWith("https://file://", StringComparison.OrdinalIgnoreCase))
            {
                url = url.Substring("https://".Length);
            }

            if (url.StartsWith("file://", StringComparison.OrdinalIgnoreCase))
            {
                url = NormalizeFileUrl(url);
            }
            else if (!url.StartsWith("http://", StringComparison.OrdinalIgnoreCase) &&
                     !url.StartsWith("https://", StringComparison.OrdinalIgnoreCase))
            {
                url = "http://" + url;
            }

            return url.EndsWith("/") ? url : url + "/";
        }

        private static string NormalizeFileUrl(string url)
        {
            string rawPath = url.Substring("file://".Length).Replace('\\', '/');
            while (rawPath.StartsWith("/") && rawPath.Length > 2 && rawPath[2] == ':')
            {
                rawPath = rawPath.Substring(1);
            }

            string localPath = Uri.UnescapeDataString(rawPath).Replace('/', Path.DirectorySeparatorChar);
            try
            {
                return new Uri(localPath).AbsoluteUri;
            }
            catch
            {
                return "file:///" + rawPath.Replace("#", "%23");
            }
        }

        // 与 LoadDll.GetFileMd5Name 同款：name.ext -> name_md5.ext
        private static string Md5Name(string filename, string md5)
        {
            int pos = filename.LastIndexOf('.');
            return pos >= 0 ? $"{filename.Substring(0, pos)}_{md5}{filename.Substring(pos)}"
                            : $"{filename}_{md5}";
        }

        private static string Md5OfBytes(byte[] data)
        {
            using (var md5 = System.Security.Cryptography.MD5.Create())
            {
                var hash = md5.ComputeHash(data);
                var sb = new System.Text.StringBuilder(hash.Length * 2);
                foreach (var b in hash) sb.Append(b.ToString("x2"));
                return sb.ToString();
            }
        }
        private static string Md5OfFile(string path) => Md5OfBytes(File.ReadAllBytes(path));

        private IEnumerator GetText(string url, Action<string> onText)
        {
            using (var uwr = UnityWebRequest.Get(url))
            {
                yield return uwr.SendWebRequest();
                onText(uwr.result == UnityWebRequest.Result.Success ? uwr.downloadHandler.text : null);
                if (uwr.result != UnityWebRequest.Result.Success)
                    Debug.LogError($"[MiniGameDownloader] GET 失败 {url}: {uwr.error}");
            }
        }

        private IEnumerator GetBytes(string url, Action<byte[]> onBytes)
        {
            using (var uwr = UnityWebRequest.Get(url))
            {
                yield return uwr.SendWebRequest();
                onBytes(uwr.result == UnityWebRequest.Result.Success ? uwr.downloadHandler.data : null);
                if (uwr.result != UnityWebRequest.Result.Success)
                    Debug.LogError($"[MiniGameDownloader] GET 失败 {url}: {uwr.error}");
            }
        }
    }
}