using Avalonia.Controls;
using System;
using Mesen.Interop;
using Mesen.Config;
using System.Collections.Generic;
using System.Threading;
using Avalonia.Threading;
using System.Linq;
using Mesen.Debugger.ViewModels;
using Mesen.Debugger.Windows;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Collections.Concurrent;
using System.Threading.Tasks;

namespace Mesen.Debugger.Utilities
{
	public static class ToolRefreshHelper
	{
		class ToolInfo
		{
			internal int ViewerId { get; set; } = 0;
			internal int Scanline { get; set; } = 0;
			internal int Cycle { get; set; } = 0;
			internal CpuType CpuType { get; set; }
		}

		public class LastRefreshInfo
		{
			public WeakReference<Window> Host;
			public DateTime Stamp;

			public LastRefreshInfo(Window host)
			{
				Host = new(host);
			}
		}

		private static List<LastRefreshInfo> _lastRefreshStamp = new();
		private static ConcurrentDictionary<Window, ToolInfo> _activeWindows = new();
		private static int _nextId = 0;

		public static void ExecuteAt(int scanline, int cycle, CpuType cpuType, Action callback)
		{
			//Execute callback at the specified scanline/cycle
			//If the callback is not called by the core within 300ms
			//call it from the UI as a fallback
			object lockObject = new();
			bool done = false;

			int viewerId = ToolRefreshHelper.GetNextId();
			NotificationListener? listener = new();
			listener.OnNotification += (NotificationEventArgs e) => {
				switch(e.NotificationType) {
					case ConsoleNotificationType.ViewerRefresh:
						if(e.Parameter.ToInt32() == viewerId) {
							lock(callback) {
								if(!done) {
									Task.Run(() => {
										//DebugApi.RemoveViewerId() must not be called inside the notification callback (which is
										//the same thread as the emulation thread). Otherwise, the viewer timing collection the
										//debugger is iterating on will be modified, causing a crash.
										DebugApi.RemoveViewerId(viewerId, cpuType);
									});

									listener.Dispose();
									listener = null;
									callback();
									done = true;
								}
							}
						}
						break;
				}
			};
			
			DebugApi.SetViewerUpdateTiming(viewerId, scanline, cycle, cpuType);

			Task.Run(async () => {
				await Task.Delay(300);
				if(listener != null) {
					lock(callback) {
						if(!done) {
							//Give up after 300ms and call the callback
							DebugApi.RemoveViewerId(viewerId, cpuType);
							callback();
							listener.Dispose();
							done = true;
						}
					}
				}
			});
		}

		private static int GetNextId()
		{
			return Interlocked.Increment(ref _nextId);
		}

		private static int RegisterWindow(Window wnd, RefreshTimingConfig cfg, CpuType cpuType)
		{
			if(_activeWindows.ContainsKey(wnd)) {
				throw new Exception("Register window called twice");
			}

			int newId = GetNextId();
			wnd.Closing += OnWindowClosingHandler;
			wnd.Closed += OnWindowClosedHandler;

			_activeWindows.TryAdd(wnd, new ToolInfo() { ViewerId = newId, Scanline = cfg.RefreshScanline, Cycle = cfg.RefreshCycle, CpuType = cpuType });

			DebugApi.SetViewerUpdateTiming(newId, cfg.RefreshScanline, cfg.RefreshCycle, cpuType);

			return newId;
		}

		private static void OnWindowClosingHandler(object? sender, CancelEventArgs e)
		{
			if(sender is Window wnd) {
				//Do this in OnClosing (before OnClosed), to call RemoveViewerId before the debugger gets
				//shut down by DebugWindowManager when closing the last debug tool window
				if(_activeWindows.TryGetValue(wnd, out ToolInfo? toolInfo)) {
					DebugApi.RemoveViewerId(toolInfo.ViewerId, toolInfo.CpuType);
				}
				wnd.Closing -= OnWindowClosingHandler;
			}
		}

		private static void OnWindowClosedHandler(object? sender, EventArgs e)
		{
			if(sender is Window wnd) {
				//Do this in OnClosed to ensure the window doesn't get re-registered by a
				//notification received between the Closing and Closed events
				_activeWindows.TryRemove(wnd, out _);
				wnd.Closed -= OnWindowClosedHandler;
			}
		}

		private static int GetViewerId(Window wnd, RefreshTimingConfig cfg, CpuType cpuType)
		{
			if(_activeWindows.TryGetValue(wnd, out ToolInfo? toolInfo)) {
				if(cfg.RefreshScanline != toolInfo.Scanline || cfg.RefreshCycle != toolInfo.Cycle) {
					toolInfo.Scanline = cfg.RefreshScanline;
					toolInfo.Cycle = cfg.RefreshCycle;
					toolInfo.CpuType = cpuType;
					DebugApi.SetViewerUpdateTiming(toolInfo.ViewerId, cfg.RefreshScanline, cfg.RefreshCycle, cpuType);
				}
				return toolInfo.ViewerId;
			} else {
				lock(_activeWindows) {
					//Lock to prevent registering the same window twice in 2 separate threads
					if(!_activeWindows.TryGetValue(wnd, out toolInfo)) {
						return RegisterWindow(wnd, cfg, cpuType);
					} else {
						return toolInfo.ViewerId;
					}
				}
			}
		}

		public static void ProcessNotification(Window wnd, NotificationEventArgs e, RefreshTimingViewModel cfg, ICpuTypeModel model, Action refresh)
		{
			int viewerId = GetViewerId(wnd, cfg.Config, model.CpuType);

			switch(e.NotificationType) {
				case ConsoleNotificationType.ViewerRefresh:
					if(cfg.Config.AutoRefresh && e.Parameter.ToInt32() == viewerId && !LimitFps(wnd, 80)) {
						refresh();
					}
					break;

				case ConsoleNotificationType.StateLoaded:
					refresh();
					break;

				case ConsoleNotificationType.CodeBreak:
					if(cfg.Config.RefreshOnBreakPause) {
						refresh();
					}
					break;

				case ConsoleNotificationType.GameLoaded:
					GameLoadedEventParams evtParams = Marshal.PtrToStructure<GameLoadedEventParams>(e.Parameter);

					if(!evtParams.IsPowerCycle) {
						//When loading a game from disk, tools need to be updated (cpu type, etc.)
						RomInfo romInfo = EmuApi.GetRomInfo();
						if(!romInfo.CpuTypes.Contains(model.CpuType)) {
							model.CpuType = romInfo.ConsoleType.GetMainCpuType();
						}
						model.OnGameLoaded();

						Dispatcher.UIThread.Post(() => {
							cfg.UpdateMinMaxValues(model.CpuType);
						});
					}

					if(_activeWindows.TryGetValue(wnd, out ToolInfo? toolInfo)) {
						toolInfo.CpuType = model.CpuType;
						DebugApi.SetViewerUpdateTiming(toolInfo.ViewerId, cfg.Config.RefreshScanline, cfg.Config.RefreshCycle, model.CpuType);
					}
					break;
			}
		}

		public static bool LimitFps(Window wnd, int maxFps)
		{
			if(_lastRefreshStamp.Count > 5) {
				//Reduce FPS by 10% for each active tool above 5 (down to 30% refresh speed)
				maxFps = Math.Max(5, (int)(maxFps * Math.Max(0.3, 1.0 - (_lastRefreshStamp.Count - 5) * 0.1)));
			}

			DateTime now = DateTime.Now;
			for(int i = _lastRefreshStamp.Count - 1; i >= 0; i--) {
				if(_lastRefreshStamp[i].Host.TryGetTarget(out Window? target)) {
					if(!DebugWindowManager.IsDebugWindow(target)) {
						//Window was closed, remove from list
						_lastRefreshStamp.RemoveAt(i);
						continue;
					}

					if(target == wnd) {
						if((now - _lastRefreshStamp[i].Stamp).TotalMilliseconds < 1000.0 / maxFps) {
							return true;
						} else {
							_lastRefreshStamp[i].Stamp = now;
							return false;
						}
					}
				} else {
					_lastRefreshStamp.RemoveAt(i);
				}
			}

			_lastRefreshStamp.Add(new LastRefreshInfo(wnd) { Stamp = now });
			return false;
		}
	}
}