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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
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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package org.scijava.command;

import java.lang.reflect.Field;

import org.scijava.Cancelable;
import org.scijava.Context;
import org.scijava.Contextual;
import org.scijava.NullContextException;
import org.scijava.module.DefaultMutableModule;
import org.scijava.plugin.Parameter;
import org.scijava.util.ClassUtils;

/**
 * A command with a variable number of inputs and outputs. This class provides
 * greater configurability, but also greater complexity, than implementing the
 * {@link Command} interface and using only @{@link Parameter} annotations on
 * instance fields.
 * 
 * @author Curtis Rueden
 */
public abstract class DynamicCommand extends DefaultMutableModule implements
	Cancelable, Command, Contextual
{

	@Parameter
	private Context context;

	@Parameter
	private CommandService commandService;

	private DynamicCommandInfo info;

	/** Reason for cancelation, or null if not canceled. */
	private String cancelReason;

	// -- Module methods --

	@Override
	public DynamicCommandInfo getInfo() {
		if (info == null) {
			// NB: Create dynamic metadata lazily.
			final CommandInfo commandInfo = commandService.getCommand(getClass());
			info = new DynamicCommandInfo(commandInfo, getClass());
		}
		return info;
	}

	@Override
	public Object getInput(final String name) {
		final Field field = getInfo().getInputField(name);
		if (field == null) return super.getInput(name);
		return ClassUtils.getValue(field, this);
	}

	@Override
	public Object getOutput(final String name) {
		final Field field = getInfo().getOutputField(name);
		if (field == null) return super.getInput(name);
		return ClassUtils.getValue(field, this);
	}

	@Override
	public void setInput(final String name, final Object value) {
		final Field field = getInfo().getInputField(name);
		if (field == null) super.setInput(name, value);
		else ClassUtils.setValue(field, this, value);
	}

	@Override
	public void setOutput(final String name, final Object value) {
		final Field field = getInfo().getOutputField(name);
		if (field == null) super.setOutput(name, value);
		else ClassUtils.setValue(field, this, value);
	}

	// -- Contextual methods --

	@Override
	public Context context() {
		if (context == null) throw new NullContextException();
		return context;
	}

	@Override
	public Context getContext() {
		return context;
	}

	@Override
	public void setContext(final Context context) {
		context.inject(this);
	}

	// -- Cancelable methods --

	@Override
	public boolean isCanceled() {
		return cancelReason != null;
	}

	@Override
	public void cancel(final String reason) {
		cancelReason = reason == null ? "" : reason;
	}

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

}