using System.Diagnostics;
using System.IO.Compression;
using System.Net;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using System.Text.Json;
using System.Text.Json.Nodes;
using System.Text.RegularExpressions;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using Proxd_man.Config;
using Proxd_man.Config.Outbound;

namespace Proxd_man;

public class XrayCoreManager(
    ILogger<XrayCoreManager> logger,
    IOptionsMonitor<ProxdConfig> config)
{
    private const string XrayLatestReleaseApiUrl = "https://api.github.com/repos/XTLS/Xray-core/releases/latest";

    private const string XrayLatestReleaseAssetDownloadUrlPrefix =
        "https://github.com/XTLS/Xray-core/releases/latest/download/";

    private string CoreProgramDir => config.CurrentValue.XrayCoreProgramDirectory;
    private string WorkingDirectory => config.CurrentValue.XrayCoreWorkingDirectory;

    // TODO: 看看注册订阅更新事件后, 需要进行哪些操作.

    public string GetXrayCoreProgramPath()
    {
        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
        {
            return CoreProgramDir + "/xray.exe";
        }

        return CoreProgramDir + "/xray";
    }

    public string GetXrayCoreProgramDownloadUrl()
    {
        string os;
        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
        {
            var osVersion = Environment.OSVersion.Version;

            switch (osVersion.Major)
            {
                case < 6:
                case 6 when osVersion.Minor < 1:
                    throw new Exception("Windows 7 or later is required.");
                case 6 when osVersion.Minor == 1:
                    os = "win7";
                    break;
                default:
                    os = "windows";
                    break;
            }
        }
        else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
        {
            os = "linux";
        }
        else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
        {
            os = "macos";
        }
        else if (RuntimeInformation.IsOSPlatform(OSPlatform.FreeBSD))
        {
            os = "freebsd";
        }
        else if (RuntimeInformation.IsOSPlatform(OSPlatform.Create("openbsd")))
        {
            os = "openbsd";
        }
        else
        {
            throw new Exception("Unsupported operating system.");
        }

        string arch;
        if (RuntimeInformation.ProcessArchitecture == Architecture.X64)
        {
            arch = "64";
        }
        else if (RuntimeInformation.ProcessArchitecture == Architecture.X86)
        {
            arch = "32";
        }
        else if (RuntimeInformation.ProcessArchitecture == Architecture.Arm)
        {
            arch = "arm32-v7a";
        }
        else if (RuntimeInformation.ProcessArchitecture == Architecture.Arm64)
        {
            arch = "arm64-v8a";
        }
        else if (RuntimeInformation.ProcessArchitecture == Architecture.Armv6)
        {
            arch = "arm32-v6";
        }
        else
        {
            throw new Exception("Unsupported architecture.");
        }

        return $"{XrayLatestReleaseAssetDownloadUrlPrefix}Xray-{os}-{arch}.zip";
    }

    private Process CreateXrayCoreProcess(string args, bool redirectOutput = true)
    {
        var programPath = GetXrayCoreProgramPath();
        if (!File.Exists(programPath))
        {
            throw new Exception("Xray-Core program not found: " + programPath);
        }

        if (!Directory.Exists(WorkingDirectory))
        {
            Directory.CreateDirectory(WorkingDirectory);
        }

        return new Process
        {
            StartInfo = new ProcessStartInfo
            {
                FileName = programPath,
                Arguments = args,
                RedirectStandardOutput = redirectOutput,
                UseShellExecute = false,
                CreateNoWindow = true,
                WorkingDirectory = WorkingDirectory
            }
        };
    }

    /// <summary>
    /// 获取目前已安装的 Xray Core 版本.
    /// </summary>
    /// <returns>如果已安装了 Xray Core 则返回对应的版本号, 否则返回 null.</returns>
    private async Task<string?> GetCurrentXrayCoreVersion()
    {
        // 检查平台, 如果是 Linux, 则检查 coreProgramDir + "/xray", 如果是 Windows, 则检查 coreProgramDir + "/xray.exe"
        var xrayCoreProgramPath = GetXrayCoreProgramPath();
        if (!File.Exists(xrayCoreProgramPath))
        {
            return null;
        }

        var process = CreateXrayCoreProcess("--version");
        process.Start();
        await process.WaitForExitAsync();
        var output = (await process.StandardOutput.ReadToEndAsync()).Trim();

        var versionMatch = Regex.Match(output, @"Xray (\d+\.\d+\.\d+)");
        return versionMatch.Success ? versionMatch.Groups[1].Value : null;
    }

    public async Task<string> GetLatestXrayCoreVersion()
    {
        using var client = new HttpClient();
        client.DefaultRequestHeaders.Add("User-Agent", "XrayCoreManager");
        var response = await client.GetAsync(XrayLatestReleaseApiUrl);

        if (response.StatusCode != HttpStatusCode.OK)
        {
            throw new Exception("Failed to get latest Xray Core version.");
        }

        using var content = await JsonDocument.ParseAsync(await response.Content.ReadAsStreamAsync());
        var root = content.RootElement;

        if (!root.TryGetProperty("tag_name", out var tagNameElement))
        {
            throw new Exception("Failed to get latest Xray Core version.");
        }

        var tagName = tagNameElement.GetString() ?? throw new Exception("Failed to get latest Xray Core version.");
        return tagName.StartsWith('v') ? tagName[1..] : tagName;
    }

    public async Task FetchXrayCoreProgram()
    {
        if (!Directory.Exists(CoreProgramDir))
        {
            Directory.CreateDirectory(CoreProgramDir);
        }

        var programArchiveUrl = GetXrayCoreProgramDownloadUrl();
        var programArchiveDigestUrl = programArchiveUrl + ".dgst";
        logger.LogDebug("Xray-Core 下载地址: {programArchiveUrl}", programArchiveUrl);
        logger.LogDebug("Xray-Core 下载地址 (Digest): {programArchiveDigestUrl}", programArchiveDigestUrl);

        var tempArchiveFile = Path.GetTempFileName();

        using var httpClient = new HttpClient();

        logger.LogDebug("正在下载 Xray-Core...");
        await using var archiveStream = await httpClient.GetStreamAsync(programArchiveUrl);
        await using (var programArchiveFileStream = new FileStream(tempArchiveFile, FileMode.Create, FileAccess.Write))
        {
            await archiveStream.CopyToAsync(programArchiveFileStream);
        }

        logger.LogDebug("正在获取 SHA-256 Digest...");
        var digests = await httpClient.GetStringAsync(programArchiveDigestUrl);
        logger.LogDebug("可用的 Digests: \n{digests}", digests);

        // digests 每行都有一个不同算法的 digest HEX 值, 因此从 digests 读出开头为 SHA-256= 的行, 并提取出其右侧的 Sha256 值
        var sha256Digest =
            digests.Split('\n').FirstOrDefault(line => line.StartsWith("SHA2-256="))?["SHA2-256=".Length..]
                ?.Trim();
        if (sha256Digest == null)
        {
            throw new Exception("Failed to get SHA-256 digest.");
        }

        logger.LogDebug("SHA-256 Digest: {sha256Digest}", sha256Digest);
        // Verify digest
        using var sha256 = SHA256.Create();

        await using (var localArchiveFileStream = new FileStream(tempArchiveFile, FileMode.Open, FileAccess.Read))
        {
            var localDigest = await sha256.ComputeHashAsync(localArchiveFileStream);
            var localDigestHex = BitConverter.ToString(localDigest).Replace("-", "").ToLower();
            logger.LogDebug("本地 SHA-256 Digest: {localDigest}", localDigestHex);

            if (localDigestHex != sha256Digest)
            {
                throw new Exception("SHA-256 digest mismatch.");
            }

            logger.LogDebug("SHA-256 Digest 验证通过.");
        }

        ZipFile.ExtractToDirectory(tempArchiveFile, CoreProgramDir, true);

        // Set permissions
        if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux) ||
            RuntimeInformation.IsOSPlatform(OSPlatform.FreeBSD))
        {
            await Process.Start("chmod", "+x " + GetXrayCoreProgramPath()).WaitForExitAsync();
        }
        else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
        {
            await Process.Start("chmod", "+x " + GetXrayCoreProgramPath()).WaitForExitAsync();
        }

        File.Delete(tempArchiveFile);
    }

    public async Task InitialXrayCoreProgram()
    {
        logger.LogInformation("正在检查 Xray-Core 安装情况以及版本...");
        var currentVersion = await GetCurrentXrayCoreVersion();
        logger.LogDebug("当前 Xray-Core 版本: {currentVersion}", currentVersion);
        var requiredUpdate = false;
        if (currentVersion == null)
        {
            requiredUpdate = true;
            logger.LogInformation("未找到 Xray-Core, 开始下载最新版本...");
        }
        else
        {
            var latestXrayCoreVersion = await GetLatestXrayCoreVersion();
            if (currentVersion != latestXrayCoreVersion)
            {
                requiredUpdate = true;
                logger.LogInformation("发现新版本 Xray-Core (Version: {latestVersion}), 开始下载最新版本...",
                    latestXrayCoreVersion);
            }
        }

        if (requiredUpdate)
        {
            await FetchXrayCoreProgram();
            logger.LogInformation("Xray-Core 更新完成.");
        }
        else
        {
            logger.LogInformation("Xray-Core 已是最新版本, 无需更新.");
        }
    }

    public async Task<bool> VerifyXrayCoreConfigFile(string configFilePath)
    {
        var process = CreateXrayCoreProcess($"run -test -config {configFilePath}");

        process.Start();
        await process.WaitForExitAsync();
        return process.ExitCode == 0;
    }

    /// <summary>
    /// 生成最终的 Xray-Core 配置 JSON 对象.
    ///
    /// 注意, 在 Xray-Core 中, Inbound 和 Outbound 的首位配置很重要.
    /// </summary>
    /// <param name="inboundConfigs">配置使用的入站设置.</param>
    /// <param name="outboundSetting">该配置使用的出站配置.</param>
    /// <param name="onlyTest"></param>
    /// <returns></returns>
    public JsonObject GenerateXrayCoreConfigJson(List<IInboundSetting> inboundConfigs,
        BaseOutboundSetting outboundSetting, bool onlyTest = false)
    {
        // 基本的设置.
        var proxyConfig = new JsonObject
        {
            {
                "log", new JsonObject
                {
                    { "loglevel", "warning" }
                }
            },
            {
                "policy", new JsonObject
                {
                    {
                        "levels", new JsonObject
                        {
                            // 给 DNS 使用的.
                            {
                                "1", new JsonObject
                                {
                                    { "connIdle", 30 }
                                }
                            }
                        }
                    },
                    {
                        "system", new JsonObject
                        {
                            { "statsOutboundDownlink", true },
                            { "statsOutboundUplink", true }
                        }
                    }
                }
            },
            { "stats", new JsonObject() }
        };

        // ------------- DNS 配置 -------------
        var directResolveDomains = new JsonArray();
        var localDnsServer = new JsonObject
        {
            { "address", "localhost" },
            { "domains", directResolveDomains },
            { "queryStrategy", "" }
        };

        if (!onlyTest)
        {
            directResolveDomains.Add("geosite:cn");
        }

        // 如果不是一个 IP 地址(v4 或 v6)，则添加到 DNS 服务器列表中
        if (!IPAddress.TryParse(outboundSetting.Address, out _))
        {
            directResolveDomains.Add($"full:{outboundSetting.Address}");
        }

        var dnsServers = new JsonArray(new JsonObject
        {
            { "address", config.CurrentValue.RemoteDnsServer },
            { "domains", new JsonArray() },
            { "queryStrategy", "" }
        }, localDnsServer);

        proxyConfig.Add("dns", new JsonObject
        {
            { "disableFallback", true },
            { "servers", dnsServers }
        });
        // ------------- DNS 配置 ↑ -------------
        // ------------ Inbound 配置 ------------

        var inbounds = new JsonArray();
        proxyConfig.Add("inbounds", inbounds);
        foreach (var inboundConfig in inboundConfigs)
        {
            inbounds.Add(inboundConfig.ToJsonSetting());
        }

        // ------------ Inbound 配置 ↑ ------------

        var outbounds = new JsonArray();
        proxyConfig.Add("outbounds", outbounds);

        var proxyOutboundSettings = outboundSetting.ToJsonSetting();
        proxyOutboundSettings.Add("domainStrategy", "AsIs");
        outbounds.Add(proxyOutboundSettings);

        outbounds.Add(new FreedomOutboundSetting("bypass")
        {
            Name = "bypass"
        }.ToJsonSetting());
        outbounds.Add(new FreedomOutboundSetting
        {
            Name = "direct"
        }.ToJsonSetting());
        outbounds.Add(new BlackholeOutboundSetting
        {
            Name = "block"
        }.ToJsonSetting());
        // 添加 DNS 出站配置, 要求 DNS 走 Proxy 代理出站.
        outbounds.Add(new JsonObject
        {
            { "protocol", "dns" },
            { "tag", "dns-out" },
            {
                "settings", new JsonObject
                {
                    { "address", "1.1.1.1" },
                    { "port", 53 },
                    { "network", "tcp" },
                    { "userLevel", 1 }
                }
            },
            {
                "proxySettings", new JsonObject
                {
                    { "tag", outboundSetting.GetTag() },
                    { "transportLayer", true }
                }
            }
        });

        // ------------ Outbound 配置 ------------
        // ------------ Routing 配置 -------------
        
        var routingSettings = new JsonObject
        {
            { "domainStrategy", "AsIs" }
        };
        proxyConfig.Add("routing", routingSettings);

        var inboundTags = new JsonArray();
        foreach (var inboundConfig in inboundConfigs)
        {
            inboundTags.Add(inboundConfig.GetTag());
        }

        var rules = new JsonArray(new JsonObject
        {
            { "inboundTag", inboundTags },
            { "outboundTag", "dns-out" },
            { "type", "field" },
            { "port", "53" }
        })
        {
            new JsonObject
            {
                { "ip", new JsonArray("geoip:cn", "geoip:private") },
                { "outboundTag", "bypass" },
                { "type", "field" },
            },
            new JsonObject
            {
                { "domain", new JsonArray("geosite:cn") },
                { "outboundTag", "bypass" },
                { "type", "field" },
            },
            new JsonObject
            {
                { "outboundTag", "proxy" },
                { "port", "0-65535" },
                { "type", "field" },
            }
        };

        routingSettings.Add("rules", rules);
        return proxyConfig;
    }

    public Process CreateOutboundTestProcess(ushort inboundHttpPort, BaseOutboundSetting outboundSetting)
    {
        var configJson = GenerateXrayCoreConfigJson([
            new HttpInboundSetting
            {
                Port = inboundHttpPort
            }
        ], outboundSetting, true);

        var configFilePath = Path.Combine(Path.Combine(WorkingDirectory, "test-config"), Path.GetRandomFileName() + ".json");
        using var configFileStream = File.CreateText(configFilePath);
        configFileStream.Write(JsonSerializer.Serialize(configJson));

        return CreateXrayCoreProcess($"run -config {configFilePath}");
    }
    
    
}