using System.Diagnostics;
using System.Text;
using ZA.CoreService.ESBCertificateManager.Models;

namespace ZA.CoreService.ESBCertificateManager.Services;

/// <summary>
/// Führt PowerShell-Befehle lokal oder via WinRM (Invoke-Command) auf dem Sonic-Server aus.
/// </summary>
public sealed class WinRmExecutor
{
    private readonly SonicConnection _connection;

    public WinRmExecutor(SonicConnection connection)
    {
        _connection = connection;
    }

    public async Task<(bool Success, string? Error)> TestConnectionAsync(
        CancellationToken cancellationToken = default)
    {
        if (_connection.ManagementMode == SonicManagementMode.LocalCmd)
        {
            (bool ok, string? output, string? error) = await RunScriptAsync(
                "$env:COMPUTERNAME", cancellationToken);
            return ok
                ? (true, null)
                : (false, $"LocalCmd fehlgeschlagen: {error ?? output}");
        }

        string host = ExtractHost(_connection.ConnectionUrl);

        try
        {
            using System.Net.Sockets.TcpClient tcp = new();
            using CancellationTokenSource cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
            cts.CancelAfter(TimeSpan.FromSeconds(Math.Clamp(_connection.TimeoutSeconds, 5, 30)));

            await tcp.ConnectAsync(host, _connection.WinRmPort, cts.Token);
        }
        catch (Exception ex) when (ex is not OperationCanceledException)
        {
            return (false,
                $"WinRM-Port {_connection.WinRmPort} auf '{host}' nicht erreichbar: {ex.Message}\n" +
                "Auf dem Zielrechner: Enable-PSRemoting -Force\n" +
                "Oder ManagementMode=LocalCmd setzen und die App auf dem Sonic-PC starten.");
        }

        (bool sessionOk, _, string? sessionError) = await RunScriptAsync(
            "$env:COMPUTERNAME", cancellationToken);

        return sessionOk
            ? (true, null)
            : (false, $"WinRM-Verbindung fehlgeschlagen: {sessionError}");
    }

    public async Task<(bool Success, string? Output, string? Error)> RunScriptAsync(
        string scriptBlock,
        CancellationToken cancellationToken = default)
    {
        string fullScript = _connection.ManagementMode == SonicManagementMode.LocalCmd
            ? BuildLocalScript(scriptBlock)
            : BuildRemoteScript(ExtractHost(_connection.ConnectionUrl), scriptBlock);

        ProcessStartInfo psi = new()
        {
            FileName = "powershell.exe",
            Arguments = "-NonInteractive -NoProfile -ExecutionPolicy Bypass -Command -",
            UseShellExecute = false,
            RedirectStandardInput = true,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            CreateNoWindow = true,
            StandardInputEncoding = Encoding.UTF8
        };

        using Process process = new() { StartInfo = psi };

        if (!process.Start())
        {
            return (false, null, "PowerShell-Prozess konnte nicht gestartet werden.");
        }

        await process.StandardInput.WriteAsync(fullScript.AsMemory(), cancellationToken);
        process.StandardInput.Close();

        using CancellationTokenSource timeoutCts =
            CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
        timeoutCts.CancelAfter(TimeSpan.FromSeconds(Math.Clamp(_connection.TimeoutSeconds, 10, 600)));

        Task<string> stdoutTask = process.StandardOutput.ReadToEndAsync(cancellationToken);
        Task<string> stderrTask = process.StandardError.ReadToEndAsync(cancellationToken);

        try
        {
            await process.WaitForExitAsync(timeoutCts.Token);
        }
        catch (OperationCanceledException) when (!cancellationToken.IsCancellationRequested)
        {
            try { process.Kill(entireProcessTree: true); } catch { /* ignore */ }
            return (false, null, $"Ausführung Timeout nach {_connection.TimeoutSeconds}s.");
        }

        string stdout = (await stdoutTask).Trim();
        string stderr = (await stderrTask).Trim();

        if (process.ExitCode == 0)
        {
            return (true, stdout, stderr.Length > 0 ? stderr : null);
        }

        return (false, stdout.Length > 0 ? stdout : null,
            stderr.Length > 0 ? Truncate(stderr) : $"PowerShell ExitCode={process.ExitCode}");
    }

    private static string BuildLocalScript(string scriptBlock)
        => "$ErrorActionPreference = 'Stop'\n" + scriptBlock;

    private string BuildRemoteScript(string host, string scriptBlock)
    {
        string escapedPwd = _connection.Password.Replace("'", "''");
        string escapedUser = _connection.Username.Replace("'", "''");
        string escapedHost = host.Replace("'", "''");

        return
            "$ErrorActionPreference = 'Stop'\n" +
            $"$secPwd = ConvertTo-SecureString '{escapedPwd}' -AsPlainText -Force\n" +
            $"$cred   = New-Object System.Management.Automation.PSCredential('{escapedUser}', $secPwd)\n" +
            $"Invoke-Command -ComputerName '{escapedHost}' -Port {_connection.WinRmPort} -Credential $cred -ScriptBlock {{\n" +
            $"    {scriptBlock}\n" +
            "} -ErrorAction Stop";
    }

    public static string ApplyScriptTemplate(
        string template,
        string containerName,
        string domainName = "",
        string sonicHome = "",
        string xapiPath = "")
        => template
            .Replace("{container}", containerName.Replace("'", "''"), StringComparison.OrdinalIgnoreCase)
            .Replace("{domain}", domainName.Replace("'", "''"), StringComparison.OrdinalIgnoreCase)
            .Replace("{sonicHome}", sonicHome.Replace("'", "''"), StringComparison.OrdinalIgnoreCase)
            .Replace("{xapiPath}", xapiPath.Replace("'", "''"), StringComparison.OrdinalIgnoreCase);

    private static string ExtractHost(string connectionUrl)
    {
        try { return new Uri(connectionUrl).Host; }
        catch { return connectionUrl; }
    }

    private static string Truncate(string s, int max = 600)
        => s.Length <= max ? s : s[..max] + "…";
}