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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.

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/*-
 * #%L
 * SciJava Common shared library for SciJava software.
 * %%
 * Copyright (C) 2009 - 2024 SciJava developers.
 * %%
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
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package org.scijava.download;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.List;

import org.scijava.io.handle.AbstractDataHandle;
import org.scijava.io.handle.DataHandle;
import org.scijava.io.location.Location;

/**
 * {@link DataHandle} plugin for writing to multiple {@link DataHandle}s.
 * 
 * @author Curtis Rueden
 */
public class MultiWriteHandle extends AbstractDataHandle {

	private final List> handles;

	public MultiWriteHandle(final DataHandle... handles) {
		this.handles = new ArrayList<>(Arrays.asList(handles));
	}

	// -- DataHandle methods --

	@Override
	public boolean isReadable() {
		return false;
	}

	@Override
	public boolean isWritable() {
		boolean writable = true;
		// NB: Somewhat arbitrarily, we are writable iff all our constituents are.
		for (final DataHandle h : handles)
			writable &= h.isWritable();
		return writable;
	}

	@Override
	public boolean exists() throws IOException {
		boolean exists = true;
		// NB: Somewhat arbitrarily, we exist iff any of our constituents exist.
		for (final DataHandle h : handles)
			exists |= h.isWritable();
		return exists;
	}

	@Override
	public Date lastModified() throws IOException {
		for (final DataHandle h : handles) {
			final Date lastModified = h.lastModified();
			if (lastModified != null) return lastModified;
		}
		return null;
	}

	@Override
	public String checksum() throws IOException {
		for (final DataHandle h : handles) {
			final String checksum = h.checksum();
			if (checksum != null) return checksum;
		}
		return null;
	}

	@Override
	public long offset() throws IOException {
		return handles.get(0).offset();
	}

	@Override
	public void seek(long pos) throws IOException {
		// TODO: parallelStream().forEach() for performance.
		for (final DataHandle h : handles)
			h.seek(pos);
	}

	@Override
	public long length() throws IOException {
		return handles.get(0).length();
	}

	@Override
	public void setLength(long length) throws IOException {
		for (final DataHandle h : handles)
			h.setLength(length);
	}

	@Override
	public int read(byte[] b, int off, int len) throws IOException {
		throw new UnsupportedOperationException();
	}

	@Override
	public Class getType() {
		return null;
	}

	@Override
	public byte readByte() throws IOException {
		throw new UnsupportedOperationException();
	}

	@Override
	public void write(final int b) throws IOException {
		// TODO: parallelStream().forEach() for performance.
		for (final DataHandle h : handles)
			h.write(b);
	}

	@Override
	public void write(byte[] b, int off, int len) throws IOException {
		// TODO: parallelStream().forEach() for performance.
		for (final DataHandle h : handles)
			h.write(b, off, len);
	}

	@Override
	public void close() throws IOException {
		// TODO: parallelStream().forEach() for performance.
		for (final DataHandle h : handles)
			h.close();
	}
}