using System;
using System.Collections.Generic;
using System.Threading;

namespace MoonWorks.Audio
{
	public class AudioDevice : IDisposable
	{
		public IntPtr Handle { get; }
		public byte[] Handle3D { get; }
		public FAudio.FAudioDeviceDetails DeviceDetails { get; }

		private IntPtr trueMasteringVoice;

		// this is a fun little trick where we use a submix voice as a "faux" mastering voice
		// this lets us maintain API consistency for effects like panning and reverb
		private SubmixVoice fauxMasteringVoice;
		public SubmixVoice MasteringVoice => fauxMasteringVoice;

		public float CurveDistanceScalar = 1f;
		public float DopplerScale = 1f;
		public float SpeedOfSound = 343.5f;

		private readonly HashSet<WeakReference> resources = new HashSet<WeakReference>();
		private readonly List<StreamingSound> autoUpdateStreamingSoundReferences = new List<StreamingSound>();
		private readonly List<WeakReference<SoundSequence>> soundSequenceReferences = new List<WeakReference<SoundSequence>>();
		private readonly List<SourceVoice> autoFreeSourceVoices = new List<SourceVoice>();

		private AudioTweenManager AudioTweenManager;

		private SourceVoicePool VoicePool;

		private const int Step = 200;
		private TimeSpan UpdateInterval;
		private System.Diagnostics.Stopwatch TickStopwatch = new System.Diagnostics.Stopwatch();
		private long previousTickTime;
		private Thread Thread;
		private AutoResetEvent WakeSignal;
		internal readonly object StateLock = new object();

		private bool Running;
		private bool IsDisposed;

		public unsafe AudioDevice()
		{
			UpdateInterval = TimeSpan.FromTicks(TimeSpan.TicksPerSecond / Step);

			FAudio.FAudioCreate(out var handle, 0, FAudio.FAUDIO_DEFAULT_PROCESSOR);
			Handle = handle;

			/* Find a suitable device */

			FAudio.FAudio_GetDeviceCount(Handle, out var devices);

			if (devices == 0)
			{
				Logger.LogError("No audio devices found!");
				FAudio.FAudio_Release(Handle);
				Handle = IntPtr.Zero;
				return;
			}

			FAudio.FAudioDeviceDetails deviceDetails;

			uint i = 0;
			for (i = 0; i < devices; i++)
			{
				FAudio.FAudio_GetDeviceDetails(
					Handle,
					i,
					out deviceDetails
				);
				if ((deviceDetails.Role & FAudio.FAudioDeviceRole.FAudioDefaultGameDevice) == FAudio.FAudioDeviceRole.FAudioDefaultGameDevice)
				{
					DeviceDetails = deviceDetails;
					break;
				}
			}

			if (i == devices)
			{
				i = 0; /* whatever we'll just use the first one I guess */
				FAudio.FAudio_GetDeviceDetails(
					Handle,
					i,
					out deviceDetails
				);
				DeviceDetails = deviceDetails;
			}

			/* Init Mastering Voice */
			var result = FAudio.FAudio_CreateMasteringVoice(
				Handle,
				out trueMasteringVoice,
				FAudio.FAUDIO_DEFAULT_CHANNELS,
				FAudio.FAUDIO_DEFAULT_SAMPLERATE,
				0,
				i,
				IntPtr.Zero
			);

			if (result != 0)
			{
				Logger.LogError("Failed to create a mastering voice!");
				Logger.LogError("Audio device creation failed!");
				return;
			}

			fauxMasteringVoice = new SubmixVoice(this, FAudio.FAUDIO_DEFAULT_CHANNELS, FAudio.FAUDIO_DEFAULT_SAMPLERATE);

			/* Init 3D Audio */

			Handle3D = new byte[FAudio.F3DAUDIO_HANDLE_BYTESIZE];
			FAudio.F3DAudioInitialize(
				DeviceDetails.OutputFormat.dwChannelMask,
				SpeedOfSound,
				Handle3D
			);

			AudioTweenManager = new AudioTweenManager();
			VoicePool = new SourceVoicePool(this);

			Logger.LogInfo("Setting up audio thread...");
			WakeSignal = new AutoResetEvent(true);

			Thread = new Thread(ThreadMain);
			Thread.IsBackground = true;
			Thread.Start();

			Running = true;

			TickStopwatch.Start();
			previousTickTime = 0;
		}

		private void ThreadMain()
		{
			while (Running)
			{
				lock (StateLock)
				{
					try
					{
						ThreadMainTick();
					}
					catch (Exception e)
					{
						Logger.LogError(e.ToString());
					}
				}

				WakeSignal.WaitOne(UpdateInterval);
			}
		}

		private void ThreadMainTick()
		{
			long tickDelta = TickStopwatch.Elapsed.Ticks - previousTickTime;
			previousTickTime = TickStopwatch.Elapsed.Ticks;
			float elapsedSeconds = (float) tickDelta / System.TimeSpan.TicksPerSecond;

			for (var i = autoUpdateStreamingSoundReferences.Count - 1; i >= 0; i -= 1)
			{
				var streamingSound = autoUpdateStreamingSoundReferences[i];

				if (streamingSound.Loaded)
				{
					streamingSound.Update();
				}
				else
				{
					autoUpdateStreamingSoundReferences.RemoveAt(i);
				}
			}

			for (var i = soundSequenceReferences.Count - 1; i >= 0; i -= 1)
			{
				if (soundSequenceReferences[i].TryGetTarget(out var soundSequence))
				{
					soundSequence.OnUpdate();
				}
				else
				{
					soundSequenceReferences.RemoveAt(i);
				}
			}

			for (var i = autoFreeSourceVoices.Count - 1; i >= 0; i -= 1)
			{
				var voice = autoFreeSourceVoices[i];
				if (voice.BuffersQueued == 0)
				{
					Return(voice);
					autoFreeSourceVoices.RemoveAt(i);
				}
			}

			AudioTweenManager.Update(elapsedSeconds);
		}

		/// <summary>
		/// Triggers all pending operations with the given syncGroup value.
		/// </summary>
		public void TriggerSyncGroup(uint syncGroup)
		{
			FAudio.FAudio_CommitChanges(Handle, syncGroup);
		}

		/// <summary>
		/// Obtains an appropriate source voice from the voice pool.
		/// </summary>
		/// <param name="format">The format that the voice must match.</param>
		/// <returns>A source voice with the given format.</returns>
		public SourceVoice Obtain(Format format)
		{
			lock (StateLock)
			{
				return VoicePool.Obtain(format);
			}
		}

		internal void ReturnWhenIdle(SourceVoice voice)
		{
			lock (StateLock)
			{
				autoFreeSourceVoices.Add(voice);
			}
		}

		/// <summary>
		/// Returns the source voice to the voice pool.
		/// </summary>
		/// <param name="voice"></param>
		internal void Return(SourceVoice voice)
		{
			lock (StateLock)
			{
				voice.Reset();
				VoicePool.Return(voice);
			}
		}

		internal void CreateTween(
			Voice voice,
			AudioTweenProperty property,
			System.Func<float, float> easingFunction,
			float start,
			float end,
			float duration,
			float delayTime
		) {
			lock (StateLock)
			{
				AudioTweenManager.CreateTween(
					voice,
					property,
					easingFunction,
					start,
					end,
					duration,
					delayTime
				);
			}
		}

		internal void ClearTweens(
			Voice voice,
			AudioTweenProperty property
		) {
			lock (StateLock)
			{
				AudioTweenManager.ClearTweens(voice, property);
			}
		}

		internal void WakeThread()
		{
			WakeSignal.Set();
		}

		internal void AddResourceReference(AudioResource resource)
		{
			lock (StateLock)
			{
				resources.Add(resource.weakReference);
			}
		}

		internal void RemoveResourceReference(AudioResource resource)
		{
			lock (StateLock)
			{
				resources.Remove(resource.weakReference);
			}
		}

		internal void AddAutoUpdateStreamingSoundInstance(StreamingSound instance)
		{
			autoUpdateStreamingSoundReferences.Add(instance);
		}

		internal void AddSoundSequenceReference(SoundSequence sequence)
		{
			soundSequenceReferences.Add(new WeakReference<SoundSequence>(sequence));
		}

		protected virtual void Dispose(bool disposing)
		{
			if (!IsDisposed)
			{
				Running = false;
				Thread.Join();

				if (disposing)
				{
					// stop all source voices
					foreach (var weakReference in resources)
					{
						var target = weakReference.Target;

						if (target != null && target is SourceVoice voice)
						{
							voice.Stop();
						}
					}

					// destroy all audio resources
					foreach (var weakReference in resources)
					{
						var target = weakReference.Target;

						if (target != null)
						{
							(target as IDisposable).Dispose();
						}
					}

					resources.Clear();
				}

				FAudio.FAudioVoice_DestroyVoice(trueMasteringVoice);
				FAudio.FAudio_Release(Handle);

				IsDisposed = true;
			}
		}

		~AudioDevice()
		{
			// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
			Dispose(disposing: false);
		}

		public void Dispose()
		{
			// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
			Dispose(disposing: true);
			GC.SuppressFinalize(this);
		}
	}
}