using System.IO;
using System;
using System.Text;

namespace CommonTools
{
	/// <summary>
	/// Code taken from this thread: https://forum.unity.com/threads/lzma-compression-and-decompression-for-unity.239285/
	/// </summary>
	public static class LZMATools
	{
		public enum LZMADictionarySize
		{
			Dict256KiB = 262144, // 2^18 = 262144 = 256 KiB
			Dict512KiB = 524288, // 2^19
			Dict1MiB = 1048576, // 2^20
			Dict2MiB = 2097152, // 2^21
			Dict4MiB = 4194304 // 2^22
		};

		#region Compress

		// First ones without dictionary size
		public static void CompressFileToLZMAFile(string inFile, string outFile)
		{
			using var input = new FileStream(inFile, FileMode.Open);
			using var output = new FileStream(outFile, FileMode.Create);

			Compress(input, output);
		}

		public static void CompressByteArrayToLZMAFile(byte[] inByteArray, string outFile)
		{
			using var input = new MemoryStream(inByteArray);
			using var output = new FileStream(outFile, FileMode.Create);

			Compress(input, output);
		}

		public static byte[] CompressByteArrayToLZMAByteArray(byte[] inByteArray)
		{
			using var input = new MemoryStream(inByteArray);
			using var output = new MemoryStream();

			Compress(input, output);
			return output.ToArray();
		}

		public static byte[] CompressUTF8StringToLZMAByteArray(string inText)
		{
			var bytes = Encoding.UTF8.GetBytes(inText);
			return CompressByteArrayToLZMAByteArray(bytes);
		}

		// Then the ones with dictionary size
		public static void CompressFileToLZMAFile(string inFile, string outFile, LZMADictionarySize dictSize)
		{
			using var input = new FileStream(inFile, FileMode.Open);
			using var output = new FileStream(outFile, FileMode.Create);

			Compress(input, output, dictSize);
		}

		public static void CompressByteArrayToLZMAFile(byte[] inByteArray, string outFile, LZMADictionarySize dictSize)
		{
			using var input = new MemoryStream(inByteArray);
			using var output = new FileStream(outFile, FileMode.Create);

			Compress(input, output, dictSize);
		}

		public static byte[] CompressByteArrayToLZMAByteArray(byte[] inByteArray, LZMADictionarySize dictSize)
		{
			using var input = new MemoryStream(inByteArray);
			using var output = new MemoryStream();

			Compress(input, output, dictSize);
			return output.ToArray();
		}

		#endregion

		#region Decompress

		public static void DecompressLZMAFileToFile(string inFile, string outFile)
		{
			using var input = new FileStream(inFile, FileMode.Open);
			using var output = new FileStream(outFile, FileMode.Create);

			Decompress(input, output);
		}

		public static void DecompressLZMAByteArrayToFile(byte[] inByteArray, string outFile)
		{
			using var input = new MemoryStream(inByteArray);
			using var output = new FileStream(outFile, FileMode.Create);

			Decompress(input, output);
		}

		public static byte[] DecompressLZMAByteArrayToByteArray(byte[] inByteArray)
		{
			using var input = new MemoryStream(inByteArray);
			using var output = new MemoryStream();

			Decompress(input, output);
			return output.ToArray();
		}

		public static string DecompressLZMAByteArrayToUTF8String(byte[] inByteArray)
		{
			var bytes = DecompressLZMAByteArrayToByteArray(inByteArray);
			return Encoding.UTF8.GetString(bytes);
		}

		#endregion

		#region Private functions

		private static void Compress(Stream inputStream, Stream outputStream)
		{
			var coder = new SevenZip.Compression.LZMA.Encoder();

			// Write encoder properties to output stream
			coder.WriteCoderProperties(outputStream);

			// Write size of input stream to output stream.
			outputStream.Write(BitConverter.GetBytes(inputStream.Length), 0, 8);

			// Encode
			coder.Code(inputStream, outputStream, inputStream.Length, -1, null);
			outputStream.Flush();
		}

		private static void Compress(Stream inputStream, Stream outputStream, LZMADictionarySize dictSize)
		{
			var coder = new SevenZip.Compression.LZMA.Encoder();
			Int32 dictSize32 = (Int32)dictSize;
			coder.SetCoderProperties(new SevenZip.CoderPropID[] {SevenZip.CoderPropID.DictionarySize}, new object[] {dictSize32});
			// Write encoder properties to output stream
			coder.WriteCoderProperties(outputStream);

			// Write size of input stream to output stream.
			outputStream.Write(BitConverter.GetBytes(inputStream.Length), 0, 8);

			// Encode
			coder.Code(inputStream, outputStream, inputStream.Length, -1, null);
			outputStream.Flush();
		}

		public static void Decompress(Stream inputStream, Stream outputStream)
		{
			var coder = new SevenZip.Compression.LZMA.Decoder();

			// Read decoder properties
			byte[] properties = new byte[5]; // 5 comes from kPropSize (LzmaEncoder.cs)
			inputStream.Read(properties, 0, 5);

			// Read the size of the output stream.
			byte[] fileLengthBytes = new byte[8];
			inputStream.Read(fileLengthBytes, 0, 8);
			long fileLength = BitConverter.ToInt64(fileLengthBytes, 0);

			// Decode
			coder.SetDecoderProperties(properties);
			coder.Code(inputStream, outputStream, inputStream.Length, fileLength, null);
			outputStream.Flush();
		}

		#endregion

	}

}