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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 - 2017 Board of Regents of the University of
 * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
 * Institute of Molecular Cell Biology and Genetics.
 * %%
 * 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.
 * #L%
 */

package org.scijava.log;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.StringJoiner;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ConcurrentSkipListMap;

/**
 * Identifies where a {@link LogMessage} came from.
 *
 * @author Matthias Arzt
 */
public class LogSource {

	public static final String SEPARATOR = ":";

	private final LogSource parent;

	private final List path;

	private final ConcurrentMap children =
		new ConcurrentSkipListMap<>();

	private String formatted = null;

	private Integer logLevel;

	private LogSource(LogSource parent, String name) {
		this.parent = parent;
		List parentPath = parent.path();
		List list = new ArrayList<>(parentPath.size() + 1);
		list.addAll(parentPath);
		list.add(name);
		this.path = Collections.unmodifiableList(list);
	}

	private LogSource() {
		this.parent = null;
		this.path = Collections.emptyList();
	}

	/** Returns the root log source. This LogSource represents the empty list. */
	public static LogSource newRoot() {
		return new LogSource();
	}

	/**
	 * Returns a log source with the given path.
	 *
	 * @param subPath Relative path to the source, divided by
	 *          {@link LogSource#SEPARATOR}.
	 */
	public LogSource subSource(final String subPath) {
		LogSource result = this;
		for (final String name : subPath.split(SEPARATOR))
			result = result.child(name);
		return result;
	}

	/** Returns the list of strings which is represented by this LogSource. */
	public List path() {
		return path;
	}

	/** Returns the last entry in the list of strings. */
	public String name() {
		if (path.isEmpty()) return "";
		return path.get(path.size() - 1);
	}

	@Override
	public String toString() {
		if (formatted != null) return formatted;
		StringJoiner joiner = new StringJoiner(SEPARATOR);
		path.forEach(s -> joiner.add(s));
		formatted = joiner.toString();
		return formatted;
	}

	public boolean isRoot() {
		return parent == null;
	}

	/** Gets the parent of this source, or null if the source is a root. */
	public LogSource parent() {
		return parent;
	}

	public void setLogLevel(int logLevel) {
		this.logLevel = logLevel;
	}

	public boolean hasLogLevel() {
		return logLevel != null;
	}

	public int logLevel() {
		if (!hasLogLevel()) throw new IllegalStateException();
		return logLevel;
	}

	// -- Helper methods --

	private LogSource child(final String name) {
		if (name.isEmpty()) return this;
		LogSource child = children.get(name);
		if (child != null) return child;
		child = new LogSource(this, name);
		children.putIfAbsent(name, child);
		return children.get(name);
	}
}