using System.Diagnostics;
using System.IO;
using Microsoft.Win32;

namespace DeskCoreSetup;

/// <summary>Installation/Deinstallation – nur für den aktuellen Benutzer, ohne Administratorrechte.</summary>
public static class Installer
{
    public const string AppName = "DeskCore";
    public const string Publisher = "M_Viper";
    public const string ExeName = "DeskCore.exe";
    public const string UninstallerName = "DeskCore-Uninstall.exe";
    private const string UninstallKey = @"Software\Microsoft\Windows\CurrentVersion\Uninstall\DeskCore";
    private const string RunKey = @"Software\Microsoft\Windows\CurrentVersion\Run";

    public static string Version
    {
        get
        {
            var v = typeof(Installer).Assembly.GetName().Version!;
            return $"{v.Major}.{v.Minor}.{v.Build}";
        }
    }

    /// <summary>Pfad dieses Setups (auch als Deinstallationsprogramm).</summary>
    public static string SelfPath => System.Reflection.Assembly.GetExecutingAssembly().Location;

    public static string DefaultDir =>
        Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "Programs", AppName);

    private static string StartMenuLink =>
        Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Programs), AppName + ".lnk");

    private static string DesktopLink =>
        Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory), AppName + ".lnk");

    /// <summary>Ordner einer vorhandenen Installation (oder null).</summary>
    public static string? InstalledDir
    {
        get
        {
            using var k = Registry.CurrentUser.OpenSubKey(UninstallKey);
            return k?.GetValue("InstallLocation") as string is { } d && File.Exists(Path.Combine(d, ExeName)) ? d : null;
        }
    }

    public static string? InstalledVersion
    {
        get
        {
            using var k = Registry.CurrentUser.OpenSubKey(UninstallKey);
            return k?.GetValue("DisplayVersion") as string;
        }
    }

    public static bool AutostartEnabled
    {
        get
        {
            using var k = Registry.CurrentUser.OpenSubKey(RunKey);
            return k?.GetValue(AppName) is string;
        }
    }

    public static bool DesktopLinkExists => File.Exists(DesktopLink);

    public static string LicenseText => ReadResourceText("payload.LICENSE.txt");

    // ---------- Installieren ----------

    public static void Install(string dir, bool desktopLink, bool autostart, IProgress<(double, string)> progress,
        bool installRuntime = false)
    {
        if (!Runtime.Is64BitWindows)
            throw new InvalidOperationException("DeskCore benötigt ein 64-Bit-Windows (Windows 10 oder 11).");
        if (installRuntime && !Runtime.IsInstalled)
        {
            // 0–60 % für die Laufzeit, Rest für DeskCore
            Runtime.Install((v, text) => progress.Report((v * 0.6, text)));
            var inner = progress;
            progress = new Scaled(inner, 0.6, 0.4);
        }

        progress.Report((0.05, "DeskCore wird beendet …"));
        CloseRunningApp();
        RemoveLegacyInstall();

        progress.Report((0.2, "Dateien werden kopiert …"));
        Directory.CreateDirectory(dir);
        var exe = Path.Combine(dir, ExeName);
        WriteResource("payload.DeskCore.exe", exe);
        WriteResource("payload.LICENSE.txt", Path.Combine(dir, "LICENSE.txt"));

        // Setup selbst als Deinstallationsprogramm ablegen
        var self = SelfPath;
        var uninstaller = Path.Combine(dir, UninstallerName);
        if (!string.Equals(Path.GetFullPath(self), Path.GetFullPath(uninstaller), StringComparison.OrdinalIgnoreCase))
        {
            MoveAside(uninstaller);
            File.Copy(self, uninstaller, overwrite: true);
        }

        progress.Report((0.55, "Verknüpfungen werden angelegt …"));
        CreateShortcut(StartMenuLink, exe);
        if (desktopLink) CreateShortcut(DesktopLink, exe);

        progress.Report((0.75, "Windows wird eingerichtet …"));
        using (var run = Registry.CurrentUser.CreateSubKey(RunKey))
        {
            if (autostart) run.SetValue(AppName, $"\"{exe}\" --minimized");
            else run.DeleteValue(AppName, throwOnMissingValue: false);
        }

        using (var k = Registry.CurrentUser.CreateSubKey(UninstallKey))
        {
            long size = new[] { exe, uninstaller, Path.Combine(dir, "LICENSE.txt") }
                .Where(File.Exists).Sum(f => new FileInfo(f).Length) / 1024;
            k.SetValue("DisplayName", AppName);
            k.SetValue("DisplayVersion", Version);
            k.SetValue("Publisher", Publisher);
            k.SetValue("DisplayIcon", $"{exe},0");
            k.SetValue("InstallLocation", dir);
            k.SetValue("UninstallString", $"\"{uninstaller}\" --uninstall");
            k.SetValue("QuietUninstallString", $"\"{uninstaller}\" --uninstall /S");
            k.SetValue("URLInfoAbout", "https://m-viper.de");
            k.SetValue("InstallDate", DateTime.Now.ToString("yyyyMMdd"));
            k.SetValue("EstimatedSize", (int)size, RegistryValueKind.DWord);
            k.SetValue("NoModify", 1, RegistryValueKind.DWord);
            k.SetValue("NoRepair", 1, RegistryValueKind.DWord);
        }

        progress.Report((1.0, "Fertig"));
    }

    // ---------- Frühere Version "DeskHub" entfernen ----------

    private const string LegacyName = "DeskHub";
    private const string LegacyUninstallKey = @"Software\Microsoft\Windows\CurrentVersion\Uninstall\DeskHub";

    /// <summary>Ordner einer alten Installation unter dem früheren Namen "DeskHub" – nur unsere eigene.</summary>
    public static string? LegacyInstallDir
    {
        get
        {
            using var k = Registry.CurrentUser.OpenSubKey(LegacyUninstallKey);
            // "DeskHub" heißt auch ein anderes Programm → nur mit unserem Herausgeber anfassen
            if (k?.GetValue("Publisher") as string != Publisher) return null;
            return k.GetValue("InstallLocation") as string;
        }
    }

    private static void RemoveLegacyInstall()
    {
        var dir = LegacyInstallDir;
        if (dir is null) return;
        var exe = Path.Combine(dir, LegacyName + ".exe");

        // nur Prozesse beenden, die wirklich aus dem alten Ordner laufen
        foreach (var p in Process.GetProcessesByName(LegacyName))
        {
            try
            {
                if (p.MainModule?.FileName is { } f && Storage_IsUnder(f, dir))
                {
                    p.Kill();
                    p.WaitForExit(10000);
                }
            }
            catch { }
        }

        DeleteIfPointsTo(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Programs), LegacyName + ".lnk"), exe);
        DeleteIfPointsTo(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory), LegacyName + ".lnk"), exe);
        using (var run = Registry.CurrentUser.OpenSubKey(RunKey, writable: true))
        {
            if (run?.GetValue(LegacyName) is string cmd && cmd.IndexOf(exe, StringComparison.OrdinalIgnoreCase) >= 0)
                run.DeleteValue(LegacyName, throwOnMissingValue: false);
        }

        foreach (var f in new[] { exe, Path.Combine(dir, "LICENSE.txt"), Path.Combine(dir, LegacyName + "-Uninstall.exe") })
            MoveAside(f);
        CleanupOldFiles(dir);
        try { Directory.Delete(dir); } catch { } // nur wenn leer
        Registry.CurrentUser.DeleteSubKeyTree(LegacyUninstallKey, throwOnMissingSubKey: false);
    }

    // ---------- Deinstallieren ----------

    public static readonly string[] DataDirs =
    [
        Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), AppName),        // Kategorien
        Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), AppName),    // Einstellungen
        Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), AppName), // Rückgängig-Zwischenablage
    ];

    public static void Uninstall(bool removeData, IProgress<(double, string)> progress)
    {
        // Nur im eingetragenen Installationsordner löschen – nie dort, wo das Setup zufällig liegt (z. B. Downloads)
        var dir = InstalledDir;
        var exe = dir is null ? "" : Path.Combine(dir, ExeName);

        progress.Report((0.1, "DeskCore wird beendet …"));
        CloseRunningApp();

        progress.Report((0.3, "Verknüpfungen werden entfernt …"));
        DeleteIfPointsTo(StartMenuLink, exe);
        DeleteIfPointsTo(DesktopLink, exe);

        progress.Report((0.45, "Windows-Einträge werden entfernt …"));
        using (var run = Registry.CurrentUser.OpenSubKey(RunKey, writable: true))
            run?.DeleteValue(AppName, throwOnMissingValue: false);
        Registry.CurrentUser.DeleteSubKeyTree(UninstallKey, throwOnMissingSubKey: false);

        if (removeData)
        {
            progress.Report((0.6, "Kategorien und Einstellungen werden in den Papierkorb gelegt …"));
            foreach (var d in DataDirs.Where(Directory.Exists))
            {
                try
                {
                    Microsoft.VisualBasic.FileIO.FileSystem.DeleteDirectory(d,
                        Microsoft.VisualBasic.FileIO.UIOption.OnlyErrorDialogs,
                        Microsoft.VisualBasic.FileIO.RecycleOption.SendToRecycleBin);
                }
                catch { }
            }
        }

        progress.Report((0.85, "Dateien werden entfernt …"));
        if (dir is null) { progress.Report((1.0, "Fertig")); return; }
        TryDelete(exe);
        TryDelete(Path.Combine(dir, "LICENSE.txt"));
        CleanupOldFiles(dir);

        // Das laufende Deinstallationsprogramm kann sich nicht selbst löschen → kurz nach dem Beenden per cmd.
        // rmdir ohne /s entfernt den Ordner nur, wenn er danach leer ist.
        var self = SelfPath;
        if (Storage_IsUnder(self, dir))
        {
            Process.Start(new ProcessStartInfo("cmd.exe",
                $"/c ping 127.0.0.1 -n 3 > nul & del /f /q \"{self}\" & del /f /q \"{Path.Combine(dir, "*.old")}\" & rmdir \"{dir}\"")
            {
                CreateNoWindow = true, UseShellExecute = false, WindowStyle = ProcessWindowStyle.Hidden,
            });
        }
        else
        {
            TryDelete(Path.Combine(dir, UninstallerName));
            try { Directory.Delete(dir); } catch { } // nur wenn leer
        }
        progress.Report((1.0, "Fertig"));
    }

    // ---------- Helfer ----------

    /// <summary>Rechnet Fortschritt 0–1 in einen Teilbereich um.</summary>
    private sealed class Scaled(IProgress<(double, string)> inner, double offset, double factor) : IProgress<(double, string)>
    {
        public void Report((double, string) value) => inner.Report((offset + value.Item1 * factor, value.Item2));
    }

    /// <summary>Laufendes DeskCore beenden (das X versteckt es nur im Infobereich).</summary>
    private static void CloseRunningApp()
    {
        foreach (var p in Process.GetProcessesByName("DeskCore"))
        {
            try
            {
                p.Kill();
                p.WaitForExit(10000);
            }
            catch { }
        }
    }

    private static void WriteResource(string name, string path)
    {
        CleanupOldFiles(Path.GetDirectoryName(path)!);
        MoveAside(path);
        for (int attempt = 1; ; attempt++)
        {
            try
            {
                using var s = typeof(Installer).Assembly.GetManifestResourceStream(name)
                              ?? throw new InvalidOperationException($"Installationsdatei {name} fehlt.");
                using var f = File.Create(path);
                s.CopyTo(f);
                return;
            }
            catch (IOException) when (attempt < 10)
            {
                Thread.Sleep(500);
            }
            catch (IOException) when (attempt >= 10)
            {
                throw new IOException($"„{Path.GetFileName(path)}“ wird noch verwendet. Bitte DeskCore beenden (Rechtsklick auf das Symbol im Infobereich → Beenden) und erneut versuchen.");
            }
        }
    }

    /// <summary>
    /// Vorhandene Datei beiseite umbenennen. Das klappt unter Windows auch dann, wenn sie noch geöffnet ist
    /// (z. B. vom Explorer für das Icon oder vom Virenscanner) – überschreiben würde dagegen fehlschlagen.
    /// </summary>
    private static void MoveAside(string path)
    {
        if (!File.Exists(path)) return;
        try { File.Delete(path); return; } catch { }
        try { File.Move(path, $"{path}.{Guid.NewGuid():N}.old"); } catch { }
    }

    /// <summary>Beiseitegelegte Dateien früherer Installationen wegräumen (sofern nicht mehr in Benutzung).</summary>
    private static void CleanupOldFiles(string dir)
    {
        if (!Directory.Exists(dir)) return;
        foreach (var f in Directory.GetFiles(dir, "*.old"))
            try { File.Delete(f); } catch { }
    }

    private static string ReadResourceText(string name)
    {
        using var s = typeof(Installer).Assembly.GetManifestResourceStream(name);
        if (s is null) return "";
        using var r = new StreamReader(s);
        return r.ReadToEnd().Trim();
    }

    private static void CreateShortcut(string link, string target)
    {
        Directory.CreateDirectory(Path.GetDirectoryName(link)!);
        dynamic shell = Activator.CreateInstance(Type.GetTypeFromProgID("WScript.Shell")!)!;
        dynamic lnk = shell.CreateShortcut(link);
        lnk.TargetPath = target;
        lnk.WorkingDirectory = Path.GetDirectoryName(target);
        lnk.IconLocation = $"{target},0";
        lnk.Description = "Desktop-Icons in Kategorien sortieren";
        lnk.Save();
    }

    private static void DeleteIfPointsTo(string link, string target)
    {
        if (!File.Exists(link)) return;
        try
        {
            dynamic shell = Activator.CreateInstance(Type.GetTypeFromProgID("WScript.Shell")!)!;
            string t = shell.CreateShortcut(link).TargetPath;
            if (!string.Equals(t, target, StringComparison.OrdinalIgnoreCase)) return;
        }
        catch { return; }
        // Explorer/Indexdienst halten Verknüpfungen manchmal kurz fest → mehrmals versuchen
        for (int i = 0; i < 10 && File.Exists(link); i++)
        {
            try { File.Delete(link); }
            catch { Thread.Sleep(300); }
        }
    }

    private static void TryDelete(string path)
    {
        try { if (File.Exists(path)) File.Delete(path); } catch { }
    }

    private static bool Storage_IsUnder(string path, string dir) =>
        (Path.GetFullPath(path)).StartsWith(Path.GetFullPath(dir).TrimEnd('\\') + "\\", StringComparison.OrdinalIgnoreCase);

    public static long DataSize()
    {
        long sum = 0;
        foreach (var d in DataDirs.Where(Directory.Exists))
        {
            try
            {
                foreach (var f in Directory.EnumerateFiles(d, "*", SearchOption.AllDirectories))
                    try { sum += new FileInfo(f).Length; } catch { }
            }
            catch { }
        }
        return sum;
    }

    public static string FormatSize(long bytes) => bytes switch
    {
        < 1024 * 1024 => $"{Math.Max(1, bytes / 1024)} KB",
        < 1024L * 1024 * 1024 => $"{bytes / 1024.0 / 1024:0.#} MB",
        _ => $"{bytes / 1024.0 / 1024 / 1024:0.##} GB",
    };
}