namespace StoicGoose.Core.Sound
{
	/* Channel 3, has optional sweep */
	public sealed class SoundChannel3
	{
		const int counterReload = 2048;
		const int sweepReload = 32 * 256;

		ushort counter;
		byte pointer;

		public byte OutputLeft { get; set; }
		public byte OutputRight { get; set; }

		int sweepCounter;
		int sweepCycles;

		readonly WaveTableReadDelegate waveTableReadDelegate;

		/* REG_SND_CH3_PITCH */
		public ushort Pitch { get; set; }
		/* REG_SND_CH3_VOL */
		public byte VolumeLeft { get; set; }
		public byte VolumeRight { get; set; }
		/* REG_SND_CTRL */
		public bool IsEnabled { get; set; }
		public bool IsSweepEnabled { get; set; }

		/* REG_SND_SWEEP_VALUE */
		public sbyte SweepValue { get; set; }
		/* REG_SND_SWEEP_TIME */
		public byte SweepTime { get; set; }

		public SoundChannel3(WaveTableReadDelegate waveTableRead) => waveTableReadDelegate = waveTableRead;

		public void Reset()
		{
			counter = counterReload;
			pointer = 0;
			OutputLeft = OutputRight = 0;

			Pitch = 0;
			VolumeLeft = VolumeRight = 0;
			IsEnabled = false;

			IsSweepEnabled = false;

			sweepCounter = 0;
			sweepCycles = sweepReload;

			SweepValue = 0;
			SweepTime = 0;
		}

		public void Step()
		{
			if (IsSweepEnabled)
			{
				sweepCycles--;
				if (sweepCycles == 0)
				{
					sweepCounter--;
					if (sweepCounter <= 0)
					{
						sweepCounter = SweepTime;
						Pitch = (ushort)(Pitch + SweepValue);
					}
				}
				sweepCycles = sweepReload;
			}

			counter--;
			if (counter == Pitch)
			{
				var data = waveTableReadDelegate((ushort)(pointer >> 1));
				if ((pointer & 0b1) == 0b1) data >>= 4;
				data &= 0x0F;

				OutputLeft = (byte)(data * VolumeLeft);
				OutputRight = (byte)(data * VolumeRight);

				pointer++;
				pointer &= 0b11111;
				counter = counterReload;
			}
		}
	}
}