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Modules for reading and writing data streams
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/*
 * Copyright 2013, 2014 Deutsche Nationalbibliothek
 *
 * Licensed under the Apache License, Version 2.0 the "License";
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.metafacture.io;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.InputStream;
import java.io.OutputStream;

import org.apache.commons.compress.compressors.CompressorException;
import org.apache.commons.compress.compressors.CompressorStreamFactory;
import org.apache.commons.io.FilenameUtils;
import org.apache.commons.io.input.ProxyInputStream;
import org.apache.commons.io.output.ProxyOutputStream;
import org.metafacture.framework.MetafactureException;

/**
 * Provides a convenient interface for using stream compressors
 * and decompressors.
 *
 * @author Christoph Böhme
 *
 */
public enum FileCompression {

	NONE {
		@Override
		public OutputStream createCompressor(final OutputStream writeTo, final String fileName) {
			return new ProxyOutputStream(writeTo);
		}

		@Override
		public InputStream createDecompressor(final InputStream readFrom) {
			return new ProxyInputStream(readFrom) {
				//nothing to do
			};
		}
	},

	AUTO {
		@Override
		public OutputStream createCompressor(final OutputStream writeTo, final String fileName) {
			if (fileName == null) {
				throw new IllegalArgumentException("fileName is required for auto-selecting compressor");
			}

			final String extension = FilenameUtils.getExtension(fileName);
			final FileCompression compressor;
			if ("gz".equalsIgnoreCase(extension)) {
				compressor = GZIP;
			} else if ("gzip".equalsIgnoreCase(extension)) {
				compressor = GZIP;
			} else if ("bz2".equalsIgnoreCase(extension)) {
				compressor = BZIP2;
			} else if ("bzip2".equalsIgnoreCase(extension)) {
				compressor = BZIP2;
			} else if ("xz".equalsIgnoreCase(extension)) {
				compressor = XZ;
			} else {
				compressor = NONE;
			}

			return compressor.createCompressor(writeTo, fileName);
		}

		@Override
		public InputStream createDecompressor(final InputStream readFrom) {
			final InputStream bufferedStream = bufferStream(readFrom);
			try {
				return APACHE_COMPRESSOR_FACTORY.createCompressorInputStream(bufferedStream);
			} catch (CompressorException e) {
				return NONE.createDecompressor(bufferedStream);
			}
		}
	},

	BZIP2 {
		@Override
		public OutputStream createCompressor(final OutputStream writeTo, final String fileName) {
			try {
				return APACHE_COMPRESSOR_FACTORY.createCompressorOutputStream(
						CompressorStreamFactory.BZIP2, bufferStream(writeTo));
			} catch (CompressorException e) {
				throw new MetafactureException(e);
			}
		}

		@Override
		public InputStream createDecompressor(final InputStream readFrom) {
			try {
				return APACHE_COMPRESSOR_FACTORY.createCompressorInputStream(
						CompressorStreamFactory.BZIP2, bufferStream(readFrom));
			} catch (CompressorException e) {
				throw new MetafactureException(e);
			}
		}
	},

	GZIP {
		@Override
		public OutputStream createCompressor(final OutputStream writeTo, final String fileName) {
			try {
				return APACHE_COMPRESSOR_FACTORY.createCompressorOutputStream(
						CompressorStreamFactory.GZIP, bufferStream(writeTo));
			} catch (CompressorException e) {
				throw new MetafactureException(e);
			}
		}

		@Override
		public InputStream createDecompressor(final InputStream readFrom) {
			try {
				return APACHE_COMPRESSOR_FACTORY.createCompressorInputStream(
						CompressorStreamFactory.GZIP, bufferStream(readFrom));
			} catch (CompressorException e) {
				throw new MetafactureException(e);
			}
		}
	},

	PACK200 {
		@Override
		public OutputStream createCompressor(final OutputStream writeTo, final String fileName) {
			try {
				return APACHE_COMPRESSOR_FACTORY.createCompressorOutputStream(
						CompressorStreamFactory.PACK200, bufferStream(writeTo));
			} catch (CompressorException e) {
				throw new MetafactureException(e);
			}
		}

		@Override
		public InputStream createDecompressor(final InputStream readFrom) {
			try {
				return APACHE_COMPRESSOR_FACTORY.createCompressorInputStream(
						CompressorStreamFactory.PACK200, bufferStream(readFrom));
			} catch (CompressorException e) {
				throw new MetafactureException(e);
			}
		}
	},

	XZ {
		@Override
		public OutputStream createCompressor(final OutputStream writeTo, final String fileName) {
			try {
				return APACHE_COMPRESSOR_FACTORY.createCompressorOutputStream(
						CompressorStreamFactory.XZ, bufferStream(writeTo));
			} catch (CompressorException e) {
				throw new MetafactureException(e);
			}
		}

		@Override
		public InputStream createDecompressor(final InputStream readFrom) {
			try {
				return APACHE_COMPRESSOR_FACTORY.createCompressorInputStream(
						CompressorStreamFactory.XZ, bufferStream(readFrom));
			} catch (CompressorException e) {
				throw new MetafactureException(e);
			}
		}
	};

	private static final CompressorStreamFactory APACHE_COMPRESSOR_FACTORY = new CompressorStreamFactory();
	private static final int BUFFER_SIZE = 8 * 1024 * 1024;

	public abstract OutputStream createCompressor(final OutputStream writeTo, final String fileName);

	public abstract InputStream createDecompressor(final InputStream readFrom);

	private static OutputStream bufferStream(final OutputStream stream) {
		if (stream instanceof BufferedOutputStream) {
			return stream;
		}
		return new BufferedOutputStream(stream, BUFFER_SIZE);
	}

	private static InputStream bufferStream(final InputStream stream) {
		if (stream instanceof BufferedInputStream) {
			return stream;
		}
		return new BufferedInputStream(stream, BUFFER_SIZE);
	}

}