using System;
using System.Diagnostics;
using System.Management;
using System.Runtime.InteropServices;
using System.Text;
using System.Text.RegularExpressions;

namespace StudioE5.SetupWizard;

public record PrerequisiteResult(
    bool WindowsCompatible,
    ulong RamMB,
    ulong FreeDiskMB,
    bool VirtualEnvironmentInstalled,
    bool PodmanInstalled,
    bool PodmanMachineReady)
{
    public bool AllReady => WindowsCompatible && RamMB >= 4096 && FreeDiskMB >= 5120 && VirtualEnvironmentInstalled && PodmanInstalled && PodmanMachineReady;
}

public static class PrerequisiteChecker
{
    public static PrerequisiteResult Check()
    {
        var wsl2Ready = IsWSL2Ready();
        var podmanMachineReady = IsPodmanMachineReady();

        // Fallback : si la machine Podman est prête, WSL2 est nécessairement fonctionnel.
        // Cela contourne les problèmes de détection WSL liés à l'encodage ou au PATH.
        var virtualEnvironmentInstalled = wsl2Ready || podmanMachineReady;

        return new PrerequisiteResult(
            WindowsCompatible: IsWindowsCompatible(),
            RamMB: GetTotalPhysicalMemoryMB(),
            FreeDiskMB: GetFreeDiskSpaceMB("C:\\"),
            VirtualEnvironmentInstalled: virtualEnvironmentInstalled,
            PodmanInstalled: IsPodmanInstalled(),
            PodmanMachineReady: podmanMachineReady
        );
    }

    private static bool IsWindowsCompatible()
    {
        var os = Environment.OSVersion;
        if (os.Platform != PlatformID.Win32NT)
            return false;

        // Windows 10 version 2004 (build 19041) or Windows 11.
        return Environment.OSVersion.Version.Build >= 19041;
    }

    private static ulong GetTotalPhysicalMemoryMB()
    {
        try
        {
            using var searcher = new ManagementObjectSearcher("SELECT TotalVisibleMemorySize FROM Win32_OperatingSystem");
            foreach (ManagementObject obj in searcher.Get())
            {
                var kb = Convert.ToUInt64(obj["TotalVisibleMemorySize"]);
                return kb / 1024;
            }
        }
        catch
        {
            // ignored
        }
        return 0;
    }

    private static ulong GetFreeDiskSpaceMB(string path)
    {
        try
        {
            var drive = new DriveInfo(Path.GetPathRoot(path) ?? path);
            return (ulong)(drive.AvailableFreeSpace / (1024 * 1024));
        }
        catch
        {
            return 0;
        }
    }

    public static bool IsWSL2Ready()
    {
        // PowerShell gère mieux l'encodage de la sortie WSL que Process.Start en C#.
        if (IsWSL2ReadyViaPowerShell())
            return true;

        // Fallback natif si PowerShell n'est pas disponible.
        return IsWSL2ReadyNative();
    }

    private static bool IsWSL2ReadyViaPowerShell()
    {
        try
        {
            var tempFile = Path.GetTempFileName();
            var script =
                "$status = & wsl.exe --status 2>&1; " +
                "$ready = ($status -match 'Version par d\\u00E9faut\\s*:\\s*2') -or " +
                "($status -match 'Default Version\\s*:\\s*2'); " +
                "$ready | Out-File -FilePath '" + tempFile + "' -Encoding utf8 -NoNewline";

            var psi = new ProcessStartInfo("powershell.exe", $"-ExecutionPolicy Bypass -Command \"{script}\"")
            {
                UseShellExecute = false,
                CreateNoWindow = true,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                StandardOutputEncoding = Encoding.UTF8,
                StandardErrorEncoding = Encoding.UTF8
            };

            using var process = Process.Start(psi);
            if (process == null) return false;
            process.WaitForExit();

            if (!File.Exists(tempFile))
                return false;

            var result = File.ReadAllText(tempFile).Trim();
            File.Delete(tempFile);

            return result.Equals("True", StringComparison.OrdinalIgnoreCase);
        }
        catch
        {
            return false;
        }
    }

    private static bool IsWSL2ReadyNative()
    {
        try
        {
            // wsl --status est plus fiable que --version pour savoir si WSL2 est prêt.
            var psi = new ProcessStartInfo("wsl.exe", "--status")
            {
                UseShellExecute = false,
                CreateNoWindow = true,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                StandardOutputEncoding = Encoding.UTF8,
                StandardErrorEncoding = Encoding.UTF8
            };
            using var process = Process.Start(psi);
            if (process == null) return false;

            var output = process.StandardOutput.ReadToEnd();
            var error = process.StandardError.ReadToEnd();
            process.WaitForExit();

            // wsl --status peut retourner un code non nul même quand l’info utile est affichée
            // (par exemple si aucune distribution n’est installée). On parse quand même.
            var combined = output + "\n" + error;
            var normalized = combined
                .Replace('\u00A0', ' ')
                .Replace('\u202F', ' ');

            if (normalized.Contains("Version par défaut : 2", StringComparison.OrdinalIgnoreCase) ||
                normalized.Contains("Default Version: 2", StringComparison.OrdinalIgnoreCase) ||
                normalized.Contains("Version défaut : 2", StringComparison.OrdinalIgnoreCase))
            {
                return true;
            }

            var defaultVersion = ParseWslDefaultVersion(combined);
            if (defaultVersion == 2)
                return true;

            // Si aucune version par défaut n'est trouvée, on tente les autres méthodes.
            return (defaultVersion == 0 && WslVersionIndicatesWsl2()) ||
                   WslListIndicatesWsl2();
        }
        catch
        {
            return false;
        }
    }

    private static bool IsWSLInstalled()
    {
        return IsWSL2Ready();
    }

    private static int ParseWslDefaultVersion(string text)
    {
        try
        {
            foreach (var rawLine in text.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries))
            {
                // Normalise les espaces insécables et les espaces multiples.
                var trimmed = rawLine
                    .Replace('\u00A0', ' ')
                    .Replace('\u202F', ' ')
                    .Trim();

                // Regex souple pour matcher :
                // - Default Version: 2
                // - Version par défaut : 2
                // - Version défaut:2
                // etc.
                var match = Regex.Match(
                    trimmed,
                    @"(?i)(?:default\s+version|version\s+(?:par\s+)?d[eé]faut)\s*[:\-]?\s*(\d+)",
                    RegexOptions.CultureInvariant);

                if (match.Success && int.TryParse(match.Groups[1].Value, out var version))
                    return version;
            }
        }
        catch
        {
            // ignored
        }
        return 0;
    }

    private static bool WslVersionIndicatesWsl2()
    {
        try
        {
            var psi = new ProcessStartInfo("wsl.exe", "--version")
            {
                UseShellExecute = false,
                CreateNoWindow = true,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                StandardOutputEncoding = Encoding.UTF8,
                StandardErrorEncoding = Encoding.UTF8
            };
            using var process = Process.Start(psi);
            if (process == null) return false;
            var output = process.StandardOutput.ReadToEnd();
            var error = process.StandardError.ReadToEnd();
            process.WaitForExit();
            if (process.ExitCode != 0) return false;

            var combined = output + "\n" + error;

            // Si la sortie mentionne explicitement WSL 2 ou un noyau 5.10+, on considère WSL2 prêt.
            return combined.Contains("WSL version: 2", StringComparison.OrdinalIgnoreCase) ||
                   combined.Contains("WSL version: 2.0", StringComparison.OrdinalIgnoreCase) ||
                   combined.Contains("Kernel version: 5.10", StringComparison.OrdinalIgnoreCase);
        }
        catch
        {
            return false;
        }
    }

    private static bool WslListIndicatesWsl2()
    {
        try
        {
            var psi = new ProcessStartInfo("wsl.exe", "--list --verbose")
            {
                UseShellExecute = false,
                CreateNoWindow = true,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                StandardOutputEncoding = Encoding.UTF8,
                StandardErrorEncoding = Encoding.UTF8
            };
            using var process = Process.Start(psi);
            if (process == null) return false;
            var output = process.StandardOutput.ReadToEnd();
            var error = process.StandardError.ReadToEnd();
            process.WaitForExit();

            var combined = output + "\n" + error;

            // Si au moins une distribution est en version 2, WSL2 est fonctionnel.
            foreach (var line in combined.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries))
            {
                var parts = line.Split(new[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries);
                if (parts.Length >= 2 && parts[^1] == "2")
                    return true;
            }

            return false;
        }
        catch
        {
            return false;
        }
    }

    public static string? GetPodmanExePath()
    {
        // 1. Chercher dans le PATH actuel du processus.
        try
        {
            var psi = new ProcessStartInfo("where.exe", "podman.exe")
            {
                UseShellExecute = false,
                CreateNoWindow = true,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                StandardOutputEncoding = Encoding.UTF8,
                StandardErrorEncoding = Encoding.UTF8
            };
            using var process = Process.Start(psi);
            if (process != null)
            {
                var output = process.StandardOutput.ReadToEnd();
                process.WaitForExit();
                if (process.ExitCode == 0)
                {
                    var firstLine = output.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries).FirstOrDefault();
                    if (!string.IsNullOrWhiteSpace(firstLine) && File.Exists(firstLine))
                        return firstLine;
                }
            }
        }
        catch
        {
            // ignored
        }

        // 2. Chercher dans les emplacements d'installation connus.
        var candidates = new[]
        {
            Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "Programs", "podman", "podman.exe"),
            Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles), "RedHat", "Podman", "podman.exe"),
            Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles), "Podman", "podman.exe"),
            Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFilesX86), "RedHat", "Podman", "podman.exe"),
            Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFilesX86), "Podman", "podman.exe"),
        };

        foreach (var candidate in candidates)
        {
            if (File.Exists(candidate))
                return candidate;
        }

        return null;
    }

    private static bool IsPodmanInstalled()
    {
        var podmanPath = GetPodmanExePath();
        if (string.IsNullOrEmpty(podmanPath))
            return false;

        try
        {
            var psi = new ProcessStartInfo(podmanPath, "--version")
            {
                UseShellExecute = false,
                CreateNoWindow = true,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                StandardOutputEncoding = Encoding.UTF8,
                StandardErrorEncoding = Encoding.UTF8
            };
            using var process = Process.Start(psi);
            if (process == null) return false;
            process.WaitForExit();
            return process.ExitCode == 0;
        }
        catch
        {
            return false;
        }
    }

    private static bool IsPodmanMachineReady()
    {
        var podmanPath = GetPodmanExePath();
        if (string.IsNullOrEmpty(podmanPath))
            return false;

        try
        {
            var psi = new ProcessStartInfo(podmanPath, "machine list --format json")
            {
                UseShellExecute = false,
                CreateNoWindow = true,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                StandardOutputEncoding = Encoding.UTF8,
                StandardErrorEncoding = Encoding.UTF8
            };
            using var process = Process.Start(psi);
            if (process == null) return false;
            var output = process.StandardOutput.ReadToEnd();
            process.WaitForExit();
            if (process.ExitCode != 0) return false;

            // Very permissive check: if podman machine list returns any JSON, we consider it ready.
            return output.TrimStart().StartsWith("[") || output.TrimStart().StartsWith("{");
        }
        catch
        {
            return false;
        }
    }
}