using System;
using StoicGoose.Core.Interfaces;

namespace StoicGoose.Core.Display
{
	public static class DisplayUtilities
	{
		// TODO: WSC high contrast mode

		private static ushort ReadMemory16(IMachine machine, uint address) => (ushort)(machine.ReadMemory(address + 1) << 8 | machine.ReadMemory(address));
		private static uint ReadMemory32(IMachine machine, uint address) => (uint)(machine.ReadMemory(address + 3) << 24 | machine.ReadMemory(address + 2) << 16 | machine.ReadMemory(address + 1) << 8 | machine.ReadMemory(address));

		public static byte ReadPixel(IMachine machine, ushort tile, int y, int x, bool isPacked, bool is4bpp, bool isColor)
		{
			/* http://perfectkiosk.net/stsws.html#color_mode */

			/* WonderSwan OR Color/Crystal in 2bpp mode */
			if (!isColor || (isColor && !is4bpp))
			{
				var data = ReadMemory16(machine, (uint)(0x2000 + (tile << 4) + ((y % 8) << 1)));
				return (byte)((((data >> 15 - (x % 8)) & 0b1) << 1 | ((data >> 7 - (x % 8)) & 0b1)) & 0b11);
			}

			/* WonderSwan Color/Crystal in 4bpp mode */
			else if (isColor && is4bpp)
			{
				/* 4bpp planar mode */
				if (!isPacked)
				{
					var data = ReadMemory32(machine, (uint)(0x4000 + ((tile & 0x03FF) << 5) + ((y % 8) << 2)));
					return (byte)((((data >> 31 - (x % 8)) & 0b1) << 3 | ((data >> 23 - (x % 8)) & 0b1) << 2 | ((data >> 15 - (x % 8)) & 0b1) << 1 | ((data >> 7 - (x % 8)) & 0b1)) & 0b1111);
				}

				/* 4bpp packed mode */
				else if (isPacked)
				{
					var data = machine.ReadMemory((ushort)(0x4000 + ((tile & 0x03FF) << 5) + ((y % 8) << 2) + ((x % 8) >> 1)));
					return (byte)((data >> 4 - (((x % 8) & 0b1) << 2)) & 0b1111);
				}
			}

			throw new Exception("Invalid display controller configuration");
		}

		public static ushort ReadColor(IMachine machine, byte paletteIdx, byte colorIdx)
		{
			var address = (uint)(0x0FE00 + (paletteIdx << 5) + (colorIdx << 1));
			return (ushort)(machine.ReadMemory(address + 1) << 8 | machine.ReadMemory(address));
		}

		private static byte DuplicateBits(int value) => (byte)((value & 0b1111) | (value & 0b1111) << 4);

		public static (byte r, byte g, byte b) GeneratePixel(byte data) => (DuplicateBits(data), DuplicateBits(data), DuplicateBits(data));
		public static (byte r, byte g, byte b) GeneratePixel(ushort data) => (DuplicateBits(data >> 8), DuplicateBits(data >> 4), DuplicateBits(data >> 0));

		public static void CopyPixel((byte r, byte g, byte b) pixel, byte[] data, int x, int y, int stride) => CopyPixel(pixel, data, ((y * stride) + x) * 4);
		public static void CopyPixel((byte r, byte g, byte b) pixel, byte[] data, long address)
		{
			data[address + 0] = pixel.r;
			data[address + 1] = pixel.g;
			data[address + 2] = pixel.b;
			data[address + 3] = 255;
		}
	}
}