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package org.daisy.dotify.common.io;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Provides an in-memory stream juggler.
 * 
 * @author Joel Håkansson
 */
public class ByteArrayStreamJuggler implements StreamJuggler {
	private final int BUF_SIZE = 65536;
	private InputStreamMaker ci;
	private ByteArrayOutputStream co;
	private final File output;
	
	/**
	 * Constructs a new instance
	 * 
	 * @param input
	 *            An existing input file
	 * @param output
	 *            An output file
	 * @throws IOException
	 *             An IOException is thrown if the input does not exist
	 *             or if the input or output is a directory.
	 */
	public ByteArrayStreamJuggler(File input, File output) throws IOException {
		if (!input.exists()) { throw new FileNotFoundException(); }
		if (!input.isFile() || (output.exists() && !output.isFile())) {
			throw new IOException("Cannot perform this operation on directories.");
		}
		this.output = output;
		this.ci = new FileInputStreamMaker(input);
		this.co = new ByteArrayOutputStream(BUF_SIZE);
	}

	@Override
	public InputStreamMaker getInputStreamMaker() {
		return ci;
	}

	@Override
	public OutputStream getOutputStream() {
		return co;
	}
	
	@Override
	public void reset() throws IOException {
		if (ci==null || co==null) {
			throw new IllegalStateException("Cannot swap after close.");
		}
		ci = new ByteArrayInputStreamMaker(co.toByteArray());
		co = new ByteArrayOutputStream(BUF_SIZE);
	}
	
	@Override
	public void close() throws IOException {
		try {
			if (co.size() > 0) {
				FileIO.copy(new ByteArrayInputStream(co.toByteArray()), new FileOutputStream(output));
			} else {
				FileIO.copy(ci.newInputStream(), new FileOutputStream(output));
			}
		} finally {
			ci = null;
			co = null;
		}
	}

}