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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 - 2016 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
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package org.scijava.module.process;

import org.scijava.Context;
import org.scijava.Priority;
import org.scijava.command.Command;
import org.scijava.module.Module;
import org.scijava.module.ModuleInfo;
import org.scijava.module.ModuleItem;
import org.scijava.plugin.Parameter;
import org.scijava.plugin.Plugin;
import org.scijava.service.Service;

/**
 * The service preprocessor automatically populates module inputs that implement
 * {@link Service}.
 * 
 * Services are obtained from this preprocessor instance's application context.
 * 
 * 
 * Many modules (e.g., most {@link Command}s) use @{@link Parameter}-annotated
 * service fields, resulting in those parameters being populated when the
 * SciJava application context is injected (via {@link Context#inject(Object)}.
 * However, some modules may have service parameters which are programmatically
 * generated (i.e., returned directly as inputs from {@link ModuleInfo#inputs()}
 * and as such not populated by context injection. E.g., this situation is the
 * case for scripts, since module inputs are parsed from the script header
 * rather than declared via the @{@link Parameter} annotation. In such cases, we
 * need this service preprocessor to fill in the service values.
 * 
 * 
 * @author Curtis Rueden
 */
@Plugin(type = PreprocessorPlugin.class,
	priority = Priority.VERY_HIGH_PRIORITY)
public class ServicePreprocessor extends AbstractPreprocessorPlugin {

	// -- ModuleProcessor methods --

	@Override
	public void process(final Module module) {
		for (final ModuleItem input : module.getInfo().inputs()) {
			if (!input.isAutoFill()) continue; // cannot auto-fill this input
			final Class type = input.getType();
			if (Service.class.isAssignableFrom(type)) {
				// input is a service
				@SuppressWarnings("unchecked")
				final ModuleItem serviceInput =
					(ModuleItem) input;
				setServiceValue(getContext(), module, serviceInput);
			}
			if (type.isAssignableFrom(getContext().getClass())) {
				// input is a compatible context
				final String name = input.getName();
				module.setInput(name, getContext());
				module.setResolved(name, true);
			}
		}
	}

	// -- Helper methods --

	private  void setServiceValue(final Context context,
		final Module module, final ModuleItem input)
	{
		final S service = context.getService(input.getType());
		input.setValue(module, service);
		module.setResolved(input.getName(), true);
	}

}