using System;
using System.IO;

/*
 * Reference arithmetic coding
 * Copyright (c) Project Nayuki
 *
 * https://www.nayuki.io/page/reference-arithmetic-coding
 * https://github.com/nayuki/Reference-arithmetic-coding
 */



/// <summary>
/// Compression application using static arithmetic coding.
/// <para>Usage: java ArithmeticCompress InputFile OutputFile</para>
/// <para>Then use the corresponding "ArithmeticDecompress" application to recreate the original input file.</para>
/// <para>Note that the application uses an alphabet of 257 symbols - 256 symbols for the byte
/// values and 1 symbol for the EOF marker. The compressed file format starts with a list
/// of 256 symbol frequencies, and then followed by the arithmetic-coded data.</para>
/// </summary>
public class ArithmeticCompress
{

	//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
	//ORIGINAL LINE: public static void main(String[] args) throws java.io.IOException
	public static void Main( string[] args )
	{
		/* @@ PORT
		// Handle command line arguments
		if (args.Length != 2)
		{
			Console.Error.WriteLine("Usage: java ArithmeticCompress InputFile OutputFile");
			Environment.Exit(1);
			return;
		}
		File inputFile = new File(args[0]);
		File outputFile = new File(args[1]);

		// Read input file once to compute symbol frequencies
		FrequencyTable freqs = getFrequencies(inputFile);
		freqs.increment(256); // EOF symbol gets a frequency of 1

		// Read input file again, compress with arithmetic coding, and write output file
		using (Stream @in = new BufferedInputStream(new FileStream(inputFile, FileMode.Open, FileAccess.Read)), BitOutputStream @out = new BitOutputStream(new BufferedOutputStream(new FileStream(outputFile, FileMode.Create, FileAccess.Write))))
		{
			writeFrequencies(@out, freqs);
			compress(freqs, @in, @out);
		}
		*/
	}


	// Returns a frequency table based on the bytes in the given file.
	// Also contains an extra entry for symbol 256, whose frequency is set to 0.
	//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
	//ORIGINAL LINE: private static FrequencyTable getFrequencies(java.io.File file) throws java.io.IOException
	private static FrequencyTable getFrequencies( string file )
	{


		FrequencyTable freqs = new SimpleFrequencyTable( new int[257] );
		using( Stream input = new BufferedStream( new FileStream( file, FileMode.Open, FileAccess.Read ) ) )
		{
			while( true )
			{
				int b = input.ReadByte();
				if( b == -1 )
				{
					break;
				}
				freqs.increment( b );
			}
		}
		return freqs;
	}


	// To allow unit testing, this method is package-private instead of private.
	//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
	//ORIGINAL LINE: static void writeFrequencies(BitOutputStream out, FrequencyTable freqs) throws java.io.IOException
	internal static void writeFrequencies( BitOutputStream @out, FrequencyTable freqs )
	{
		for( int i = 0; i < 256; i++ )
		{
			writeInt( @out, 32, freqs.get( i ) );
		}
	}


	// To allow unit testing, this method is package-private instead of private.
	//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
	//ORIGINAL LINE: static void compress(FrequencyTable freqs, java.io.InputStream in, BitOutputStream out) throws java.io.IOException
	internal static void compress( FrequencyTable freqs, Stream @in, BitOutputStream @out )
	{
		ArithmeticEncoder enc = new ArithmeticEncoder( 32, @out );
		while( true )
		{
			int symbol = @in.ReadByte();
			if( symbol == -1 )
			{
				break;
			}
			enc.write( freqs, symbol );
		}
		enc.write( freqs, 256 ); // EOF
		enc.finish(); // Flush remaining code bits
	}


	// Writes an unsigned integer of the given bit width to the given stream.
	//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
	//ORIGINAL LINE: private static void writeInt(BitOutputStream out, int numBits, int value) throws java.io.IOException
	private static void writeInt( BitOutputStream @out, int numBits, int value )
	{
		if( numBits < 0 || numBits > 32 )
		{
			throw new System.ArgumentException();
		}

		for( int i = numBits - 1; i >= 0; i-- )
		{
			@out.write( ( (int)( (uint)value >> i ) ) & 1 ); // Big endian
		}
	}

}