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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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/*
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 * 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.
 * %%
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 * 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.
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package org.scijava.widget;

import org.scijava.Priority;
import org.scijava.module.Module;
import org.scijava.module.ModuleCanceledException;
import org.scijava.module.ModuleException;
import org.scijava.module.ModuleItem;

/**
 * An input harvester collects {@link Module} input values, according to the
 * following steps:
 * 
 * Create an {@link InputPanel} with widgets corresponding to the module
 * inputs.
 * Present the panel, if in a UI context.
 * Harvest the final widget values from the panel, updating the
 * {@link Module}'s input values to match the harvested values.
 * Perform any other needed processing of the results (marking inputs as
 * resolved, storing persisted values to preferences, etc.).
 * 
 * 
 * @author Curtis Rueden
 * @param  The type of UI component housing the input panel itself.
 * @param  The type of UI component housing each input widget.
 */
public interface InputHarvester {

	double PRIORITY = Priority.VERY_LOW;

	/**
	 * Performs the harvesting process.
	 * 
	 * @param module The module whose inputs should be harvest.
	 * @throws ModuleException If the process goes wrong, or is canceled.
	 */
	default void harvest(final Module module) throws ModuleException {
		final InputPanel inputPanel = createInputPanel();
		buildPanel(inputPanel, module);
		if (!inputPanel.hasWidgets()) return; // no inputs left to harvest

		final boolean ok = harvestInputs(inputPanel, module);
		if (!ok) throw new ModuleCanceledException();

		processResults(inputPanel, module);
	}

	/**
	 * Constructs an empty {@link InputPanel}. Widgets are added later using the
	 * {@link #buildPanel} method.
	 */
	InputPanel createInputPanel();

	/**
	 * Populates the given {@link InputPanel} with widgets corresponding to the
	 * given {@link Module} instance.
	 * 
	 * @param inputPanel The panel to populate.
	 * @param module The module whose inputs should be translated into widgets.
	 * @throws ModuleException if the panel cannot be populated for some reason.
	 *           This may occur due to an input of unsupported type.
	 */
	void buildPanel(InputPanel inputPanel, Module module)
		throws ModuleException;

	/**
	 * Gathers input values from the user or other source. For example, a
	 * graphical user interface could present a dialog box.
	 */
	boolean harvestInputs(InputPanel inputPanel, Module module);

	/** Does any needed processing, after input values have been harvested. */
	@SuppressWarnings("unused")
	default void processResults(final InputPanel inputPanel,
		final Module module) throws ModuleException
	{
		final Iterable> inputs = module.getInfo().inputs();

		for (final ModuleItem item : inputs) {
			final String name = item.getName();
			module.resolveInput(name);
		}
	}
}