/*
 * #%L
 * ImageJ software for multidimensional image processing and analysis.
 * %%
 * Copyright (C) 2009 - 2012 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.
 * 
 * The views and conclusions contained in the software and documentation are
 * those of the authors and should not be interpreted as representing official
 * policies, either expressed or implied, of any organization.
 * #L%
 */

package imagej.ext.plugin;

import imagej.ext.Priority;
import imagej.ext.module.Module;
import imagej.ext.module.ModuleInfo;
import imagej.ext.plugin.process.PreprocessorPlugin;

/**
 * A preprocessor plugin that verifies module validity. If the module is not
 * valid, the module execution is canceled.
 * 
 * @author Curtis Rueden
 */
@Plugin(type = PreprocessorPlugin.class,
	priority = Priority.VERY_HIGH_PRIORITY + 1)
public class ValidityPreprocessor implements PreprocessorPlugin {

	// -- Fields --

	private boolean canceled;
	private String message;

	// -- ModulePreprocessor methods --

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

	@Override
	public String getMessage() {
		return message;
	}

	// -- ModuleProcessor methods --

	@Override
	public void process(final Module module) {
		final ModuleInfo info = module.getInfo();

		canceled = !info.isValid();
		if (!canceled) return;

		final StringBuilder sb =
			new StringBuilder("The module \"" + info.getDelegateClassName() +
				"\" is invalid:\n");
		for (final String problem : info.getProblems()) {
			sb.append("- " + problem);
			sb.append("\n");
		}
		message = sb.toString();
	}

}

Add preprocessor that verifies module validity