using System.ComponentModel;
using System.Diagnostics;
using System.Text;

namespace Zcbot.WindowsNode;

internal static class ManagedRuntimeInstaller
{
    private const string DefaultIndexUrl = "https://pypi.tuna.tsinghua.edu.cn/simple/";
    private static readonly ProcessSupervisor ProcessSupervisor = new();

    internal static async Task<RuntimeInstallResult> InstallAsync(
        SoftwareDefinition definition,
        IProgress<string> progress,
        CancellationToken cancellationToken)
    {
        if (AdapterCatalog.HasActiveExecution)
        {
            throw new InvalidOperationException(
                $"{definition.DisplayName} 仍有任务在执行，暂不能更换运行环境。");
        }
        var location = SoftwareLocationService.ResolveLocation(definition);
        if (!location.Available)
        {
            throw new InvalidOperationException(
                $"尚未检测到 {definition.DisplayName}：{location.Detail}");
        }

        var requirements = ResolveBundledFile(definition.RequirementsRelativePath);
        var root = NodePaths.ForCurrentMachine().RootDirectory;
        var runtimes = Path.Combine(root, "runtimes");
        Directory.CreateDirectory(runtimes);
        NodeConfigStore.RestrictDirectory(root);

        var runtime = Path.Combine(runtimes, definition.RuntimeId);
        var staging = Path.Combine(
            runtimes,
            $".{definition.RuntimeId}.installing-{Guid.NewGuid():N}");
        var backup = Path.Combine(
            runtimes,
            $".{definition.RuntimeId}.rollback-{Guid.NewGuid():N}");
        var stagingPython = Path.Combine(staging, "Scripts", "python.exe");
        var movedExisting = false;
        try
        {
            progress.Report("正在查找 Python 3.12…");
            var bootstrap = await FindPython312Async(cancellationToken);
            progress.Report("正在创建隔离运行环境…");
            await RunAsync(
                bootstrap.FileName,
                bootstrap.PrefixArguments.Concat(["-m", "venv", staging]),
                AppContext.BaseDirectory,
                progress,
                cancellationToken);
            if (!File.Exists(stagingPython))
            {
                throw new InvalidDataException("Python venv 未生成 Scripts\\python.exe。");
            }

            await VerifyPython312Async(stagingPython, cancellationToken);
            progress.Report("正在安装 adapter 依赖…");
            var indexUrl = Environment.GetEnvironmentVariable("ZCBOT_PIP_INDEX_URL");
            if (string.IsNullOrWhiteSpace(indexUrl))
            {
                indexUrl = DefaultIndexUrl;
            }
            await RunAsync(
                stagingPython,
                ["-m", "pip", "install", "--index-url", indexUrl, "--requirement", requirements],
                AppContext.BaseDirectory,
                progress,
                cancellationToken);

            if (Directory.Exists(runtime))
            {
                Directory.Move(runtime, backup);
                movedExisting = true;
            }
            Directory.Move(staging, runtime);
            if (movedExisting)
            {
                Directory.Delete(backup, recursive: true);
            }
            NodeConfigStore.RestrictDirectory(runtime);
            return new RuntimeInstallResult(
                Path.Combine(runtime, "Scripts", "python.exe"),
                $"{definition.DisplayName} 运行环境安装完成。");
        }
        catch
        {
            if (movedExisting && !Directory.Exists(runtime) && Directory.Exists(backup))
            {
                Directory.Move(backup, runtime);
            }
            throw;
        }
        finally
        {
            DeleteDirectoryIfPresent(staging);
            DeleteDirectoryIfPresent(backup);
        }
    }

    private static string ResolveBundledFile(string relativePath)
    {
        var root = Path.GetFullPath(AppContext.BaseDirectory);
        var path = Path.GetFullPath(Path.Combine(root, relativePath));
        if (!path.StartsWith(root, StringComparison.OrdinalIgnoreCase) || !File.Exists(path))
        {
            throw new InvalidDataException("Adapter requirements 文件缺失或路径非法。");
        }
        return path;
    }

    private static async Task<BootstrapPython> FindPython312Async(
        CancellationToken cancellationToken)
    {
        var candidates = new[]
        {
            new BootstrapPython("py.exe", ["-3.12"]),
            new BootstrapPython("python.exe", []),
        };
        foreach (var candidate in candidates)
        {
            try
            {
                await RunAsync(
                    candidate.FileName,
                    candidate.PrefixArguments.Concat(
                        ["-c", "import sys; raise SystemExit(0 if sys.version_info[:2] == (3, 12) else 1)"]),
                    AppContext.BaseDirectory,
                    progress: null,
                    cancellationToken);
                return candidate;
            }
            catch (Exception exception) when (
                exception is InvalidOperationException or Win32Exception)
            {
                // Try the next fixed Python 3.12 discovery method.
            }
        }
        throw new InvalidOperationException(
            "未找到 Python 3.12。请先安装 Python 3.12 并启用 py launcher 或加入 PATH。");
    }

    private static Task VerifyPython312Async(string python, CancellationToken cancellationToken) =>
        RunAsync(
            python,
            ["-c", "import sys; raise SystemExit(0 if sys.version_info[:2] == (3, 12) else 1)"],
            AppContext.BaseDirectory,
            progress: null,
            cancellationToken);

    private static async Task RunAsync(
        string filename,
        IEnumerable<string> arguments,
        string workingDirectory,
        IProgress<string>? progress,
        CancellationToken cancellationToken)
    {
        var startInfo = new ProcessStartInfo
        {
            FileName = filename,
            WorkingDirectory = workingDirectory,
            UseShellExecute = false,
            CreateNoWindow = true,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            StandardOutputEncoding = Encoding.UTF8,
            StandardErrorEncoding = Encoding.UTF8,
        };
        foreach (var argument in arguments)
        {
            startInfo.ArgumentList.Add(argument);
        }
        startInfo.Environment["PYTHONUTF8"] = "1";
        startInfo.Environment["PYTHONIOENCODING"] = "utf-8";
        using var process = ProcessSupervisor.Start(
            startInfo, "运行环境安装进程未启动。");
        var stdout = ProcessSupervisor.CaptureOutputAsync(process.StandardOutput, progress);
        var stderr = ProcessSupervisor.CaptureOutputAsync(process.StandardError, progress);
        try
        {
            await process.WaitForExitAsync(cancellationToken);
        }
        catch (OperationCanceledException)
        {
            await ProcessSupervisor.TerminateTreeAsync(process);
            throw;
        }
        await Task.WhenAll(stdout, stderr);
        if (process.ExitCode != 0)
        {
            throw new InvalidOperationException(
                $"运行环境安装进程失败，退出码 {process.ExitCode}。");
        }
    }

    private static void DeleteDirectoryIfPresent(string path)
    {
        try
        {
            if (Directory.Exists(path)) Directory.Delete(path, recursive: true);
        }
        catch (Exception exception) when (exception is IOException or UnauthorizedAccessException)
        {
            // A successful runtime swap must not be reported as failed only because
            // antivirus software still holds a handle to the disposable directory.
        }
    }

    private sealed record BootstrapPython(
        string FileName,
        IReadOnlyList<string> PrefixArguments);
}