#region References
using System;
using System.Runtime.InteropServices;
#endregion

namespace Server.Network
{
	/// <summary>
	///     Handles outgoing packet compression for the network.
	/// </summary>
	public static class Compression
	{
		private static readonly int[] _huffmanTable = new int[514]
		{
			0x2, 0x000, 0x5, 0x01F, 0x6, 0x022, 0x7, 0x034, 0x7, 0x075, 0x6, 0x028, 0x6, 0x03B, 0x7, 0x032, 0x8, 0x0E0, 0x8,
			0x062, 0x7, 0x056, 0x8, 0x079, 0x9, 0x19D, 0x8, 0x097, 0x6, 0x02A, 0x7, 0x057, 0x8, 0x071, 0x8, 0x05B, 0x9, 0x1CC,
			0x8, 0x0A7, 0x7, 0x025, 0x7, 0x04F, 0x8, 0x066, 0x8, 0x07D, 0x9, 0x191, 0x9, 0x1CE, 0x7, 0x03F, 0x9, 0x090, 0x8,
			0x059, 0x8, 0x07B, 0x8, 0x091, 0x8, 0x0C6, 0x6, 0x02D, 0x9, 0x186, 0x8, 0x06F, 0x9, 0x093, 0xA, 0x1CC, 0x8, 0x05A,
			0xA, 0x1AE, 0xA, 0x1C0, 0x9, 0x148, 0x9, 0x14A, 0x9, 0x082, 0xA, 0x19F, 0x9, 0x171, 0x9, 0x120, 0x9, 0x0E7, 0xA,
			0x1F3, 0x9, 0x14B, 0x9, 0x100, 0x9, 0x190, 0x6, 0x013, 0x9, 0x161, 0x9, 0x125, 0x9, 0x133, 0x9, 0x195, 0x9, 0x173,
			0x9, 0x1CA, 0x9, 0x086, 0x9, 0x1E9, 0x9, 0x0DB, 0x9, 0x1EC, 0x9, 0x08B, 0x9, 0x085, 0x5, 0x00A, 0x8, 0x096, 0x8,
			0x09C, 0x9, 0x1C3, 0x9, 0x19C, 0x9, 0x08F, 0x9, 0x18F, 0x9, 0x091, 0x9, 0x087, 0x9, 0x0C6, 0x9, 0x177, 0x9, 0x089,
			0x9, 0x0D6, 0x9, 0x08C, 0x9, 0x1EE, 0x9, 0x1EB, 0x9, 0x084, 0x9, 0x164, 0x9, 0x175, 0x9, 0x1CD, 0x8, 0x05E, 0x9,
			0x088, 0x9, 0x12B, 0x9, 0x172, 0x9, 0x10A, 0x9, 0x08D, 0x9, 0x13A, 0x9, 0x11C, 0xA, 0x1E1, 0xA, 0x1E0, 0x9, 0x187,
			0xA, 0x1DC, 0xA, 0x1DF, 0x7, 0x074, 0x9, 0x19F, 0x8, 0x08D, 0x8, 0x0E4, 0x7, 0x079, 0x9, 0x0EA, 0x9, 0x0E1, 0x8,
			0x040, 0x7, 0x041, 0x9, 0x10B, 0x9, 0x0B0, 0x8, 0x06A, 0x8, 0x0C1, 0x7, 0x071, 0x7, 0x078, 0x8, 0x0B1, 0x9, 0x14C,
			0x7, 0x043, 0x8, 0x076, 0x7, 0x066, 0x7, 0x04D, 0x9, 0x08A, 0x6, 0x02F, 0x8, 0x0C9, 0x9, 0x0CE, 0x9, 0x149, 0x9,
			0x160, 0xA, 0x1BA, 0xA, 0x19E, 0xA, 0x39F, 0x9, 0x0E5, 0x9, 0x194, 0x9, 0x184, 0x9, 0x126, 0x7, 0x030, 0x8, 0x06C,
			0x9, 0x121, 0x9, 0x1E8, 0xA, 0x1C1, 0xA, 0x11D, 0xA, 0x163, 0xA, 0x385, 0xA, 0x3DB, 0xA, 0x17D, 0xA, 0x106, 0xA,
			0x397, 0xA, 0x24E, 0x7, 0x02E, 0x8, 0x098, 0xA, 0x33C, 0xA, 0x32E, 0xA, 0x1E9, 0x9, 0x0BF, 0xA, 0x3DF, 0xA, 0x1DD,
			0xA, 0x32D, 0xA, 0x2ED, 0xA, 0x30B, 0xA, 0x107, 0xA, 0x2E8, 0xA, 0x3DE, 0xA, 0x125, 0xA, 0x1E8, 0x9, 0x0E9, 0xA,
			0x1CD, 0xA, 0x1B5, 0x9, 0x165, 0xA, 0x232, 0xA, 0x2E1, 0xB, 0x3AE, 0xB, 0x3C6, 0xB, 0x3E2, 0xA, 0x205, 0xA, 0x29A,
			0xA, 0x248, 0xA, 0x2CD, 0xA, 0x23B, 0xB, 0x3C5, 0xA, 0x251, 0xA, 0x2E9, 0xA, 0x252, 0x9, 0x1EA, 0xB, 0x3A0, 0xB,
			0x391, 0xA, 0x23C, 0xB, 0x392, 0xB, 0x3D5, 0xA, 0x233, 0xA, 0x2CC, 0xB, 0x390, 0xA, 0x1BB, 0xB, 0x3A1, 0xB, 0x3C4,
			0xA, 0x211, 0xA, 0x203, 0x9, 0x12A, 0xA, 0x231, 0xB, 0x3E0, 0xA, 0x29B, 0xB, 0x3D7, 0xA, 0x202, 0xB, 0x3AD, 0xA,
			0x213, 0xA, 0x253, 0xA, 0x32C, 0xA, 0x23D, 0xA, 0x23F, 0xA, 0x32F, 0xA, 0x11C, 0xA, 0x384, 0xA, 0x31C, 0xA, 0x17C,
			0xA, 0x30A, 0xA, 0x2E0, 0xA, 0x276, 0xA, 0x250, 0xB, 0x3E3, 0xA, 0x396, 0xA, 0x18F, 0xA, 0x204, 0xA, 0x206, 0xA,
			0x230, 0xA, 0x265, 0xA, 0x212, 0xA, 0x23E, 0xB, 0x3AC, 0xB, 0x393, 0xB, 0x3E1, 0xA, 0x1DE, 0xB, 0x3D6, 0xA, 0x31D,
			0xB, 0x3E5, 0xB, 0x3E4, 0xA, 0x207, 0xB, 0x3C7, 0xA, 0x277, 0xB, 0x3D4, 0x8, 0x0C0, 0xA, 0x162, 0xA, 0x3DA, 0xA,
			0x124, 0xA, 0x1B4, 0xA, 0x264, 0xA, 0x33D, 0xA, 0x1D1, 0xA, 0x1AF, 0xA, 0x39E, 0xA, 0x24F, 0xB, 0x373, 0xA, 0x249,
			0xB, 0x372, 0x9, 0x167, 0xA, 0x210, 0xA, 0x23A, 0xA, 0x1B8, 0xB, 0x3AF, 0xA, 0x18E, 0xA, 0x2EC, 0x7, 0x062, 0x4,
			0x00D
		};

		private const int CountIndex = 0;
		private const int ValueIndex = 1;

		// UO packets may not exceed 64kb in length
		private const int BufferSize = 0x10000;

		// Optimal compression ratio is 2 / 8;  worst compression ratio is 11 / 8
		private const int MinimalCodeLength = 2;
		private const int MaximalCodeLength = 11;

		// Fixed overhead, in bits, per compression call
		private const int TerminalCodeLength = 4;

		// If our input exceeds this length, we cannot possibly compress it within the buffer
		private const int DefiniteOverflow = ((BufferSize * 8) - TerminalCodeLength) / MinimalCodeLength;

		// If our input exceeds this length, we may potentially overflow the buffer
		private const int PossibleOverflow = ((BufferSize * 8) - TerminalCodeLength) / MaximalCodeLength;

		public static unsafe void Compress(byte[] input, int offset, int count, byte[] output, ref int length)
		{
			if (input == null)
			{
				throw new ArgumentNullException("input");
			}
			else if (offset < 0 || offset >= input.Length)
			{
				throw new ArgumentOutOfRangeException("offset");
			}
			else if (count < 0 || count > input.Length)
			{
				throw new ArgumentOutOfRangeException("count");
			}
			else if ((input.Length - offset) < count)
			{
				throw new ArgumentException();
			}

			length = 0;

			if (count > DefiniteOverflow)
			{
				return;
			}

			var bitCount = 0;
			var bitValue = 0;

			fixed (int* pTable = _huffmanTable)
			{
				int* pEntry;

				fixed (byte* pInputBuffer = input)
				{
					byte* pInput = pInputBuffer + offset, pInputEnd = pInput + count;

					fixed (byte* pOutputBuffer = output)
					{
						byte* pOutput = pOutputBuffer, pOutputEnd = pOutput + BufferSize;

						while (pInput < pInputEnd)
						{
							pEntry = &pTable[*pInput++ << 1];

							bitCount += pEntry[CountIndex];

							bitValue <<= pEntry[CountIndex];
							bitValue |= pEntry[ValueIndex];

							while (bitCount >= 8)
							{
								bitCount -= 8;

								if (pOutput < pOutputEnd)
								{
									*pOutput++ = (byte)(bitValue >> bitCount);
								}
								else
								{
									length = 0;
									return;
								}
							}
						}

						// terminal code
						pEntry = &pTable[0x200];

						bitCount += pEntry[CountIndex];

						bitValue <<= pEntry[CountIndex];
						bitValue |= pEntry[ValueIndex];

						// align on byte boundary
						if ((bitCount & 7) != 0)
						{
							bitValue <<= 8 - (bitCount & 7);
							bitCount += 8 - (bitCount & 7);
						}

						while (bitCount >= 8)
						{
							bitCount -= 8;

							if (pOutput < pOutputEnd)
							{
								*pOutput++ = (byte)(bitValue >> bitCount);
							}
							else
							{
								length = 0;
								return;
							}
						}

						length = (int)(pOutput - pOutputBuffer);
						return;
					}
				}
			}
		}

		public static readonly ICompressor Compressor;

		static Compression()
		{
			if (Core.Unix)
			{
				if (Core.Is64Bit)
				{
					Compressor = new CompressorUnix64();
				}
				else
				{
					Compressor = new CompressorUnix32();
				}
			}
			else if (Core.Is64Bit)
			{
				Compressor = new Compressor64();
			}
			else
			{
				Compressor = new Compressor32();
			}
		}

		public static ZLibError Pack(byte[] dest, ref int destLength, byte[] source, int sourceLength)
		{
			return Compressor.Compress(dest, ref destLength, source, sourceLength);
		}

		public static ZLibError Pack(byte[] dest, ref int destLength, byte[] source, int sourceLength, ZLibQuality quality)
		{
			return Compressor.Compress(dest, ref destLength, source, sourceLength, quality);
		}

		public static ZLibError Unpack(byte[] dest, ref int destLength, byte[] source, int sourceLength)
		{
			return Compressor.Decompress(dest, ref destLength, source, sourceLength);
		}
	}

	public interface ICompressor
	{
		string Version { get; }

		ZLibError Compress(byte[] dest, ref int destLength, byte[] source, int sourceLength);
		ZLibError Compress(byte[] dest, ref int destLength, byte[] source, int sourceLength, ZLibQuality quality);

		ZLibError Decompress(byte[] dest, ref int destLength, byte[] source, int sourceLength);
	}

	public sealed class Compressor32 : ICompressor
	{
		internal class SafeNativeMethods
		{
			[DllImport("zlibwapi32")]
			static internal extern string zlibVersion();

			[DllImport("zlibwapi32")]
			static internal extern ZLibError compress(byte[] dest, ref int destLength, byte[] source, int sourceLength);

			[DllImport("zlibwapi32")]
			static internal extern ZLibError compress2(
				byte[] dest, ref int destLength, byte[] source, int sourceLength, ZLibQuality quality);

			[DllImport("zlibwapi32")]
			static internal extern ZLibError uncompress(byte[] dest, ref int destLen, byte[] source, int sourceLen);
		}

		public string Version => SafeNativeMethods.zlibVersion();

		public ZLibError Compress(byte[] dest, ref int destLength, byte[] source, int sourceLength)
		{
			return SafeNativeMethods.compress(dest, ref destLength, source, sourceLength);
		}

		public ZLibError Compress(byte[] dest, ref int destLength, byte[] source, int sourceLength, ZLibQuality quality)
		{
			return SafeNativeMethods.compress2(dest, ref destLength, source, sourceLength, quality);
		}

		public ZLibError Decompress(byte[] dest, ref int destLength, byte[] source, int sourceLength)
		{
			return SafeNativeMethods.uncompress(dest, ref destLength, source, sourceLength);
		}
	}

	public sealed class Compressor64 : ICompressor
	{
		internal class SafeNativeMethods
		{
			[DllImport("zlibwapi64")]
			static internal extern string zlibVersion();

			[DllImport("zlibwapi64")]
			static internal extern ZLibError compress(byte[] dest, ref int destLength, byte[] source, int sourceLength);

			[DllImport("zlibwapi64")]
			static internal extern ZLibError compress2(
				byte[] dest, ref int destLength, byte[] source, int sourceLength, ZLibQuality quality);

			[DllImport("zlibwapi64")]
			static internal extern ZLibError uncompress(byte[] dest, ref int destLen, byte[] source, int sourceLen);
		}

		public string Version => SafeNativeMethods.zlibVersion();

		public ZLibError Compress(byte[] dest, ref int destLength, byte[] source, int sourceLength)
		{
			return SafeNativeMethods.compress(dest, ref destLength, source, sourceLength);
		}

		public ZLibError Compress(byte[] dest, ref int destLength, byte[] source, int sourceLength, ZLibQuality quality)
		{
			return SafeNativeMethods.compress2(dest, ref destLength, source, sourceLength, quality);
		}

		public ZLibError Decompress(byte[] dest, ref int destLength, byte[] source, int sourceLength)
		{
			return SafeNativeMethods.uncompress(dest, ref destLength, source, sourceLength);
		}
	}

	public sealed class CompressorUnix32 : ICompressor
	{
		internal class SafeNativeMethods
		{
			[DllImport("libz")]
			static internal extern string zlibVersion();

			[DllImport("libz")]
			static internal extern ZLibError compress(byte[] dest, ref int destLength, byte[] source, int sourceLength);

			[DllImport("libz")]
			static internal extern ZLibError compress2(
				byte[] dest, ref int destLength, byte[] source, int sourceLength, ZLibQuality quality);

			[DllImport("libz")]
			static internal extern ZLibError uncompress(byte[] dest, ref int destLen, byte[] source, int sourceLen);
		}

		public string Version => SafeNativeMethods.zlibVersion();

		public ZLibError Compress(byte[] dest, ref int destLength, byte[] source, int sourceLength)
		{
			return SafeNativeMethods.compress(dest, ref destLength, source, sourceLength);
		}

		public ZLibError Compress(byte[] dest, ref int destLength, byte[] source, int sourceLength, ZLibQuality quality)
		{
			return SafeNativeMethods.compress2(dest, ref destLength, source, sourceLength, quality);
		}

		public ZLibError Decompress(byte[] dest, ref int destLength, byte[] source, int sourceLength)
		{
			return SafeNativeMethods.uncompress(dest, ref destLength, source, sourceLength);
		}
	}

	public sealed class CompressorUnix64 : ICompressor
	{
		internal class SafeNativeMethods
		{
			[DllImport("libz")]
			static internal extern string zlibVersion();

			[DllImport("libz")]
			static internal extern ZLibError compress(byte[] dest, ref long destLength, byte[] source, long sourceLength);

			[DllImport("libz")]
			static internal extern ZLibError compress2(byte[] dest, ref long destLength, byte[] source, long sourceLength, ZLibQuality quality);

			[DllImport("libz")]
			static internal extern ZLibError uncompress(byte[] dest, ref long destLen, byte[] source, long sourceLen);
		}

		public string Version => SafeNativeMethods.zlibVersion();

		public ZLibError Compress(byte[] dest, ref int destLength, byte[] source, int sourceLength)
		{
			long destLengthLong = destLength;
			var z = SafeNativeMethods.compress(dest, ref destLengthLong, source, sourceLength);
			destLength = (int)destLengthLong;
			return z;
		}

		public ZLibError Compress(byte[] dest, ref int destLength, byte[] source, int sourceLength, ZLibQuality quality)
		{
			long destLengthLong = destLength;
			var z = SafeNativeMethods.compress2(dest, ref destLengthLong, source, sourceLength, quality);
			destLength = (int)destLengthLong;
			return z;
		}

		public ZLibError Decompress(byte[] dest, ref int destLength, byte[] source, int sourceLength)
		{
			long destLengthLong = destLength;
			var z = SafeNativeMethods.uncompress(dest, ref destLengthLong, source, sourceLength);
			destLength = (int)destLengthLong;
			return z;
		}
	}

	public enum ZLibError
	{
		VersionError = -6,
		BufferError = -5,
		MemoryError = -4,
		DataError = -3,
		StreamError = -2,
		FileError = -1,

		Okay = 0,

		StreamEnd = 1,
		NeedDictionary = 2
	}

	public enum ZLibQuality
	{
		Default = -1,

		None = 0,

		Speed = 1,
		Size = 9
	}
}