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 * SciJava Common shared library for SciJava software.
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 * Institute of Molecular Cell Biology and Genetics, University of
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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 = 2 * Priority.VERY_HIGH)
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.resolveInput(name);
			}
		}
	}

	// -- 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.resolveInput(input.getName());
	}

}