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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, Max Planck
 * Institute of Molecular Cell Biology and Genetics, University of
 * Konstanz, and KNIME GmbH.
 * %%
 * 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
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package org.scijava.task;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

import org.scijava.event.EventService;
import org.scijava.task.event.TaskEvent;
import org.scijava.thread.ThreadService;

/**
 * Default implementation of {@link Task}. It launches code via the linked
 * {@link ThreadService}, and reports status updates via the linked
 * {@link EventService}.
 *
 * @author Curtis Rueden
 */
public class DefaultTask implements Task {

	private final ThreadService threadService;
	private final EventService eventService;

	private Future future;

	private boolean canceled;
	private String cancelReason;

	private String status;
	private long step;
	private long max;

	private String name;

	/**
	 * Creates a new task.
	 * 
	 * @param threadService Service to use for launching the task in its own
	 *          thread. Required.
	 * @param eventService Service to use for reporting status updates as
	 *          {@link TaskEvent}s. May be null, in which case no events are
	 *          reported.
	 */
	public DefaultTask(final ThreadService threadService,
		final EventService eventService)
	{
		this.threadService = threadService;
		this.eventService = eventService;
	}

	// -- Task methods --

	@Override
	public void run(final Runnable r) {
		if (r == null) throw new NullPointerException();
		future(r);
	}

	@Override
	public void waitFor() throws InterruptedException, ExecutionException {
		future().get();
	}

	@Override
	public boolean isDone() {
		return future != null && future.isDone();
	}

	@Override
	public String getStatusMessage() {
		return status;
	}

	@Override
	public long getProgressValue() {
		return step;
	}

	@Override
	public long getProgressMaximum() {
		return max;
	}

	@Override
	public void setStatusMessage(final String status) {
		this.status = status;
		fireTaskEvent();
	}

	@Override
	public void setProgressValue(final long step) {
		this.step = step;
		fireTaskEvent();
	}

	@Override
	public void setProgressMaximum(final long max) {
		this.max = max;
		fireTaskEvent();
	}

	// -- Cancelable methods --

	@Override
	public boolean isCanceled() {
		return canceled;
	}

	@Override
	public void cancel(final String reason) {
		canceled = true;
		cancelReason = reason;
	}

	@Override
	public String getCancelReason() {
		return cancelReason;
	}

	// -- Named methods --

	@Override
	public String getName() {
		return name;
	}

	@Override
	public void setName(final String name) {
		this.name = name;
	}

	// -- Helper methods --

	private Future future() {
		return future(null);
	}

	private Future future(final Runnable r) {
		if (future == null) initFuture(r);
		return future;
	}

	private synchronized void initFuture(final Runnable r) {
		if (future != null) return;
		if (r == null) throw new IllegalArgumentException("Must call run first");
		future = threadService.run(r);
	}

	private void fireTaskEvent() {
		if (eventService != null) eventService.publish(new TaskEvent(this));
	}
}