using Microsoft.Win32;
using System;
using System.Threading;
using System.Windows;

namespace Bedtimer
{
    public sealed class OverlayManager : IDisposable
    {
        private Config _cfg = null!;
        private OverlayWindow? _overlay;
        private Thread? _cfgThread;
        private string _cycleId = "";

        public void Start()
        {
            _cfg = Config.LoadOrCreate();
            BuildOverlay();
            StartConfigListener();

            // React to system time changes / DST
            SystemEvents.TimeChanged += (_, __) => Application.Current.Dispatcher.Invoke(RecomputeSchedule);
        }

        private void BuildOverlay()
        {
            Application.Current.Dispatcher.Invoke(() =>
            {
                _overlay ??= new OverlayWindow();
                _overlay.Show();             // safe: collapsed until T-60
                RecomputeSchedule();
            });
        }

        private void StartConfigListener()
        {
            _cfgThread = new Thread(() =>
            {
                using var ev = Signals.SubscribeConfigChanged();
                while (true)
                {
                    ev.WaitOne();
                    Application.Current.Dispatcher.Invoke(RecomputeSchedule);
                }
            });
            _cfgThread.IsBackground = true;
            _cfgThread.Start();
        }

        private void RecomputeSchedule()
        {
            _cfg = Config.LoadOrCreate();

            var now = DateTime.Now;
            var bedToday = now.Date.AddMinutes(_cfg.BedMinutes);
            var bedT = (now <= bedToday) ? bedToday : bedToday.AddDays(1);

            var warnT = bedT.AddMinutes(-_cfg.WarnLead);
            var flashT = bedT.AddMinutes(-_cfg.FlashLead);
            var lockT = bedT.AddMinutes(+_cfg.LockDelay);

            // one lock per calendar day (next bedtime’s date)
            _cycleId = bedT.ToString("yyyy-MM-dd");

            _overlay!.SetSchedule(_cycleId, warnT, flashT, bedT, lockT);
        }

        public void Dispose()
        {
            // overlay lives/dies with app; nothing extra
        }
    }
}