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

namespace Bedtimer
{
    public static class AutoStart
    {
        private const string RunKey = @"SOFTWARE\Microsoft\Windows\CurrentVersion\Run";
        private const string ValueName = "Bedtimer";

        // Public API used by UI
        public static bool IsEnabled() => ExistsHKLM();

        public static void SetEnabled(bool enabled)
        {
            try
            {
                if (enabled) EnsureHKLM();
                else DisableHKLM();
            }
            catch (UnauthorizedAccessException)
            {
                // Relaunch self elevated to write HKLM
                var exe = Environment.ProcessPath!;
                var args = enabled ? "--autostart-admin on" : "--autostart-admin off";
                Process.Start(new ProcessStartInfo(exe, args)
                {
                    UseShellExecute = true,
                    Verb = "runas"
                });
            }
        }

        // Branch the app handles on startup (see App.xaml.cs patch below)
        public static void HandleAdminArgs(string[] args)
        {
            // args: ["--autostart-admin", "on"|"off"]
            if (args.Length >= 3 && args[1] == "--autostart-admin")
            {
                if (string.Equals(args[2], "on", StringComparison.OrdinalIgnoreCase)) EnsureHKLM();
                else DisableHKLM();
                Environment.Exit(0);
            }
        }

        // -------- Internal HKLM helpers (explicit registry view) --------
        private static RegistryKey OpenHKLM()
        {
            var view = Environment.Is64BitOperatingSystem ? RegistryView.Registry64 : RegistryView.Registry32;
            return RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, view);
        }

        private static bool ExistsHKLM()
        {
            using var root = OpenHKLM();
            using var key = root.OpenSubKey(RunKey, false);
            return key?.GetValue(ValueName) is string;
        }

        private static void EnsureHKLM()
        {
            using var root = OpenHKLM();
            using var key = root.CreateSubKey(RunKey, true);
            var exe = Environment.ProcessPath!;
            var target = $"\"{exe}\"";              // no args; single EXE handles all
            key.SetValue(ValueName, target, RegistryValueKind.String);

            // (Optional) Clean up any old per-user Run entries so we don't double-start
            try
            {
                using var hkcu = Registry.CurrentUser.CreateSubKey(RunKey, true);
                hkcu.DeleteValue(ValueName, false);
            }
            catch { /* ignore */ }
        }

        private static void DisableHKLM()
        {
            using var root = OpenHKLM();
            using var key = root.CreateSubKey(RunKey, true);
            key.DeleteValue(ValueName, false);
        }
    }
}