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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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 * Wisconsin-Madison, Broad Institute of MIT and Harvard, Max Planck
 * Institute of Molecular Cell Biology and Genetics, University of
 * Konstanz, and KNIME GmbH.
 * %%
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 * 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.
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package org.scijava.log;

import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

import org.scijava.service.AbstractService;

/**
 * Base class for {@link LogService} implementations.
 *
 * @author Johannes Schindelin
 * @author Curtis Rueden
 * @author Matthias Arzt
 */
@IgnoreAsCallingClass
public abstract class AbstractLogService extends AbstractService implements
	LogService
{

	private int currentLevel = levelFromEnvironment();

	private final Map classAndPackageLevels;

	private final Logger rootLogger;

	// -- constructor --

	public AbstractLogService() {
		this(System.getProperties());
	}

	public AbstractLogService(final Properties properties) {
		rootLogger = new RootLogger();
		// provide this constructor to enable unit tests
		final int level = LogLevel.value(properties.getProperty(
			LogService.LOG_LEVEL_PROPERTY));
		if (level >= 0) currentLevel = level;
		classAndPackageLevels = setupMapFromProperties(properties,
			LogService.LOG_LEVEL_PROPERTY + ":");
		initLogSourceLevels(properties);
	}

	// -- AbstractLogService methods --

	@Override
	public void setLevel(final int level) {
		currentLevel = level;
	}

	@Override
	public void setLevel(final String classOrPackageName, final int level) {
		classAndPackageLevels.put(classOrPackageName, level);
	}

	@Override
	public void setLevelForLogger(final String source, final int level) {
		rootLogger.getSource().subSource(source).setLogLevel(level);
	}

	abstract protected void messageLogged(LogMessage message);

	// -- Logger methods --

	@Override
	public void alwaysLog(final int level, final Object msg, final Throwable t) {
		rootLogger.alwaysLog(level, msg, t);
	}

	@Override
	public LogSource getSource() {
		return rootLogger.getSource();
	}

	@Override
	public int getLevel() {
		if (classAndPackageLevels.isEmpty()) return currentLevel;
		return getLevelForClass(CallingClassUtils.getCallingClass().getName(),
			currentLevel);
	}

	@Override
	public Logger subLogger(String name, int level) {
		return rootLogger.subLogger(name, level);
	}

	@Override
	public void addLogListener(final LogListener listener) {
		rootLogger.addLogListener(listener);
	}

	@Override
	public void removeLogListener(final LogListener listener) {
		rootLogger.removeLogListener(listener);
	}

	@Override
	public void notifyListeners(final LogMessage event) {
		rootLogger.notifyListeners(event);
	}

	// -- Deprecated --

	/** @deprecated Use {@link LogLevel#prefix(int)} instead. */
	@Deprecated
	protected String getPrefix(final int level) {
		return "[" + LogLevel.prefix(level) + "]";
	}

	// -- Helper methods --

	private void initLogSourceLevels(Properties properties) {
		Map nameLevels = setupMapFromProperties(properties,
			LOG_LEVEL_BY_SOURCE_PROPERTY + ":");
		nameLevels.forEach(this::setLevelForLogger);
	}

	private int getLevelForClass(String classOrPackageName, int defaultLevel) {
		// check for a custom log level for calling class or its parent packages
		while (classOrPackageName != null) {
			final Integer level = classAndPackageLevels.get(classOrPackageName);
			if (level != null) return level;
			classOrPackageName = parentPackage(classOrPackageName);
		}
		return defaultLevel;
	}

	private String parentPackage(final String classOrPackageName) {
		final int dot = classOrPackageName.lastIndexOf(".");
		if (dot < 0) return null;
		return classOrPackageName.substring(0, dot);
	}

	private int levelFromEnvironment() {
		// use the default, which is INFO unless the DEBUG env. variable is set
		return System.getenv("DEBUG") == null ? LogLevel.INFO : LogLevel.DEBUG;
	}

	private Map setupMapFromProperties(Properties properties,
		String prefix)
	{
		final HashMap map = new HashMap<>();
		for (final String propName : properties.stringPropertyNames())
			if (propName.startsWith(prefix)) {
				final String key = propName.substring(prefix.length());
				map.put(key, LogLevel.value(properties.getProperty(propName)));
			}
		return map;
	}

	// -- Helper classes --

	@IgnoreAsCallingClass
	private class RootLogger extends DefaultLogger {

		public RootLogger() {
			super(AbstractLogService.this::messageLogged, LogSource.newRoot(),
				LogLevel.NONE);
		}

		@Override
		public int getLevel() {
			return AbstractLogService.this.getLevel();
		}
	}
}