using System;
using System.Runtime.InteropServices;
using EasingFunction = System.Func<float, float>;

namespace MoonWorks.Audio
{
	public abstract class SoundInstance : AudioResource
	{
		internal IntPtr Voice;
		internal FAudio.FAudioWaveFormatEx Format;

		protected FAudio.F3DAUDIO_DSP_SETTINGS dspSettings;

		private ReverbEffect ReverbEffect;
		private FAudio.FAudioVoiceSends ReverbSends;

		public bool Is3D { get; protected set; }

		public virtual SoundState State { get; protected set; }

		private float pan = 0;
		public float Pan
		{
			get => pan;
			internal set
			{
				if (pan != value)
				{
					pan = value;

					if (pan < -1f)
					{
						pan = -1f;
					}
					if (pan > 1f)
					{
						pan = 1f;
					}

					if (Is3D) { return; }

					SetPanMatrixCoefficients();
					FAudio.FAudioVoice_SetOutputMatrix(
						Voice,
						Device.MasteringVoice,
						dspSettings.SrcChannelCount,
						dspSettings.DstChannelCount,
						dspSettings.pMatrixCoefficients,
						0
					);
				}
			}
		}

		private float pitch = 0;
		public float Pitch
		{
			get => pitch;
			internal set
			{
				if (pitch != value)
				{
					pitch = Math.MathHelper.Clamp(value, -1f, 1f);
					UpdatePitch();
				}
			}
		}

		private float volume = 1;
		public float Volume
		{
			get => volume;
			internal set
			{
				if (volume != value)
				{
					volume = value;
					FAudio.FAudioVoice_SetVolume(Voice, volume, 0);
				}
			}
		}

		private const float MAX_FILTER_FREQUENCY = 1f;
		private const float MAX_FILTER_ONEOVERQ = 1.5f;

		private FAudio.FAudioFilterParameters filterParameters = new FAudio.FAudioFilterParameters
		{
			Type = FAudio.FAudioFilterType.FAudioLowPassFilter,
			Frequency = 1f,
			OneOverQ = 1f
		};

		public float FilterFrequency
		{
			get => filterParameters.Frequency;
			internal set
			{
				if (filterParameters.Frequency != value)
				{
					value = System.Math.Clamp(value, 0.01f, MAX_FILTER_FREQUENCY);
					filterParameters.Frequency = value;

					FAudio.FAudioVoice_SetFilterParameters(
						Voice,
						ref filterParameters,
						0
					);
				}
			}
		}

		private float FilterOneOverQ
		{
			get => filterParameters.OneOverQ;
			set
			{
				value = System.Math.Clamp(value, 0.01f, MAX_FILTER_ONEOVERQ);
				filterParameters.OneOverQ = value;

				FAudio.FAudioVoice_SetFilterParameters(
					Voice,
					ref filterParameters,
					0
				);
			}
		}

		private FilterType filterType;
		public FilterType FilterType
		{
			get => filterType;
			set
			{
				if (filterType != value)
				{
					filterType = value;

					switch (filterType)
					{
						case FilterType.None:
							filterParameters = new FAudio.FAudioFilterParameters
							{
								Type = FAudio.FAudioFilterType.FAudioLowPassFilter,
								Frequency = 1f,
								OneOverQ = 1f
							};
							break;

						case FilterType.LowPass:
							filterParameters.Type = FAudio.FAudioFilterType.FAudioLowPassFilter;
							break;

						case FilterType.BandPass:
							filterParameters.Type = FAudio.FAudioFilterType.FAudioBandPassFilter;
							break;

						case FilterType.HighPass:
							filterParameters.Type = FAudio.FAudioFilterType.FAudioHighPassFilter;
							break;
					}

					FAudio.FAudioVoice_SetFilterParameters(
						Voice,
						ref filterParameters,
						0
					);
				}
			}
		}

		private float reverb;
		public unsafe float Reverb
		{
			get => reverb;
			internal set
			{
				if (ReverbEffect != null)
				{
					if (reverb != value)
					{
						reverb = value;

						float* outputMatrix = (float*) dspSettings.pMatrixCoefficients;
						outputMatrix[0] = reverb;
						if (dspSettings.SrcChannelCount == 2)
						{
							outputMatrix[1] = reverb;
						}

						FAudio.FAudioVoice_SetOutputMatrix(
							Voice,
							ReverbEffect.Voice,
							dspSettings.SrcChannelCount,
							1,
							dspSettings.pMatrixCoefficients,
							0
						);
					}
				}

				#if DEBUG
				if (ReverbEffect == null)
				{
					Logger.LogWarn("Tried to set reverb value before applying a reverb effect");
				}
				#endif
			}
		}

		public unsafe SoundInstance(
			AudioDevice device,
			ushort formatTag,
			ushort bitsPerSample,
			ushort blockAlign,
			ushort channels,
			uint samplesPerSecond
		) : base(device)
		{
			var format = new FAudio.FAudioWaveFormatEx
			{
				wFormatTag = formatTag,
				wBitsPerSample = bitsPerSample,
				nChannels = channels,
				nBlockAlign = blockAlign,
				nSamplesPerSec = samplesPerSecond,
				nAvgBytesPerSec = blockAlign * samplesPerSecond
			};

			Format = format;

			FAudio.FAudio_CreateSourceVoice(
				Device.Handle,
				out Voice,
				ref Format,
				FAudio.FAUDIO_VOICE_USEFILTER,
				FAudio.FAUDIO_DEFAULT_FREQ_RATIO,
				IntPtr.Zero,
				IntPtr.Zero,
				IntPtr.Zero
			);

			if (Voice == IntPtr.Zero)
			{
				Logger.LogError("SoundInstance failed to initialize!");
				return;
			}

			InitDSPSettings(Format.nChannels);

			State = SoundState.Stopped;
		}

		public void Apply3D(AudioListener listener, AudioEmitter emitter)
		{
			Is3D = true;

			emitter.emitterData.CurveDistanceScaler = Device.CurveDistanceScalar;
			emitter.emitterData.ChannelCount = dspSettings.SrcChannelCount;

			FAudio.F3DAudioCalculate(
				Device.Handle3D,
				ref listener.listenerData,
				ref emitter.emitterData,
				FAudio.F3DAUDIO_CALCULATE_MATRIX | FAudio.F3DAUDIO_CALCULATE_DOPPLER,
				ref dspSettings
			);

			UpdatePitch();
			FAudio.FAudioVoice_SetOutputMatrix(
				Voice,
				Device.MasteringVoice,
				dspSettings.SrcChannelCount,
				dspSettings.DstChannelCount,
				dspSettings.pMatrixCoefficients,
				0
			);
		}

		public unsafe void ApplyReverb(ReverbEffect reverbEffect)
		{
			ReverbSends = new FAudio.FAudioVoiceSends();
			ReverbSends.SendCount = 2;
			ReverbSends.pSends = (nint) NativeMemory.Alloc((nuint) (2 * Marshal.SizeOf<FAudio.FAudioSendDescriptor>()));

			FAudio.FAudioSendDescriptor* sendDesc = (FAudio.FAudioSendDescriptor*) ReverbSends.pSends;
			sendDesc[0].Flags = 0;
			sendDesc[0].pOutputVoice = Device.MasteringVoice;
			sendDesc[1].Flags = 0;
			sendDesc[1].pOutputVoice = reverbEffect.Voice;

			FAudio.FAudioVoice_SetOutputVoices(
				Voice,
				ref ReverbSends
			);

			ReverbEffect = reverbEffect;
		}

		// TODO: since we're using setters now, could just get rid of the property setters

		public void SetPan(float targetValue)
		{
			Pan = targetValue;
		}

		public void SetPan(float targetValue, float duration, EasingFunction easingFunction)
		{
			Device.CreateTween(this, AudioTweenProperty.Pan, easingFunction, Pan, targetValue, duration);
		}

		public void SetPitch(float targetValue)
		{
			Pitch = targetValue;
		}

		public void SetPitch(float targetValue, float duration, EasingFunction easingFunction)
		{
			Device.CreateTween(this, AudioTweenProperty.Pitch, easingFunction, Pan, targetValue, duration);
		}

		public void SetVolume(float targetValue)
		{
			Volume = targetValue;
		}

		public void SetVolume(float targetValue, float duration, EasingFunction easingFunction)
		{
			Device.CreateTween(this, AudioTweenProperty.Volume, easingFunction, Volume, targetValue, duration);
		}

		public void SetFilterFrequency(float targetValue)
		{
			FilterFrequency = targetValue;
		}

		public void SetFilterFrequency(float targetValue, float duration, EasingFunction easingFunction)
		{
			Device.CreateTween(this, AudioTweenProperty.FilterFrequency, easingFunction, FilterFrequency, targetValue, duration);
		}

		public void SetReverb(float targetValue)
		{
			Reverb = targetValue;
		}

		public void SetReverb(float targetValue, float duration, EasingFunction easingFunction)
		{
			Device.CreateTween(this, AudioTweenProperty.Reverb, easingFunction, Volume, targetValue, duration);
		}

		public abstract void Play();
		public abstract void QueueSyncPlay();
		public abstract void Pause();
		public abstract void Stop();
		public abstract void StopImmediate();

		private unsafe void InitDSPSettings(uint srcChannels)
		{
			dspSettings = new FAudio.F3DAUDIO_DSP_SETTINGS();
			dspSettings.DopplerFactor = 1f;
			dspSettings.SrcChannelCount = srcChannels;
			dspSettings.DstChannelCount = Device.DeviceDetails.OutputFormat.Format.nChannels;

			nuint memsize = (
				4 *
				dspSettings.SrcChannelCount *
				dspSettings.DstChannelCount
			);

			dspSettings.pMatrixCoefficients = (nint) NativeMemory.Alloc(memsize);
			byte* memPtr = (byte*) dspSettings.pMatrixCoefficients;
			for (uint i = 0; i < memsize; i += 1)
			{
				memPtr[i] = 0;
			}

			SetPanMatrixCoefficients();
		}

		private void UpdatePitch()
		{
			float doppler;
			float dopplerScale = Device.DopplerScale;
			if (!Is3D || dopplerScale == 0.0f)
			{
				doppler = 1.0f;
			}
			else
			{
				doppler = dspSettings.DopplerFactor * dopplerScale;
			}

			FAudio.FAudioSourceVoice_SetFrequencyRatio(
				Voice,
				(float) System.Math.Pow(2.0, pitch) * doppler,
				0
			);
		}

		// Taken from https://github.com/FNA-XNA/FNA/blob/master/src/Audio/SoundEffectInstance.cs
		private unsafe void SetPanMatrixCoefficients()
		{
			/* Two major things to notice:
			 * 1. The spec assumes any speaker count >= 2 has Front Left/Right.
			 * 2. Stereo panning is WAY more complicated than you think.
			 *    The main thing is that hard panning does NOT eliminate an
			 *    entire channel; the two channels are blended on each side.
			 * -flibit
			 */
			float* outputMatrix = (float*) dspSettings.pMatrixCoefficients;
			if (dspSettings.SrcChannelCount == 1)
			{
				if (dspSettings.DstChannelCount == 1)
				{
					outputMatrix[0] = 1.0f;
				}
				else
				{
					outputMatrix[0] = (pan > 0.0f) ? (1.0f - pan) : 1.0f;
					outputMatrix[1] = (pan < 0.0f) ? (1.0f + pan) : 1.0f;
				}
			}
			else
			{
				if (dspSettings.DstChannelCount == 1)
				{
					outputMatrix[0] = 1.0f;
					outputMatrix[1] = 1.0f;
				}
				else
				{
					if (pan <= 0.0f)
					{
						// Left speaker blends left/right channels
						outputMatrix[0] = 0.5f * pan + 1.0f;
						outputMatrix[1] = 0.5f * -pan;
						// Right speaker gets less of the right channel
						outputMatrix[2] = 0.0f;
						outputMatrix[3] = pan + 1.0f;
					}
					else
					{
						// Left speaker gets less of the left channel
						outputMatrix[0] = -pan + 1.0f;
						outputMatrix[1] = 0.0f;
						// Right speaker blends right/left channels
						outputMatrix[2] = 0.5f * pan;
						outputMatrix[3] = 0.5f * -pan + 1.0f;
					}
				}
			}
		}

		protected unsafe override void Destroy()
		{
			StopImmediate();
			FAudio.FAudioVoice_DestroyVoice(Voice);
			NativeMemory.Free((void*) dspSettings.pMatrixCoefficients);

			if (ReverbEffect != null)
			{
				NativeMemory.Free((void*) ReverbSends.pSends);
			}
		}
	}
}