/*******************************************************************************
 * Copyright (c) 2000, 2013 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.debug.internal.ui.stringsubstitution;

import java.text.MessageFormat;
import java.util.HashMap;
import java.util.Map;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionPoint;
import org.eclipse.core.runtime.Platform;
import org.eclipse.core.variables.IStringVariable;
import org.eclipse.debug.internal.ui.DebugUIPlugin;
import org.eclipse.debug.ui.stringsubstitution.IArgumentSelector;

/**
 * Manages argument selectors (choosers) for string variables.
 *
 * @since 3.0
 */
public class StringVariablePresentationManager {

	/**
	 * String variable presentation extension point identifier
	 * (value <code>"stringVariablePresentations"</code>).
	 *
	 * @since 3.0
	 */
	public static final String EXTENSION_POINT_STRING_VARIABLE_PRESENTATIONS = "stringVariablePresentations"; //$NON-NLS-1$

	// default manager
	private static StringVariablePresentationManager fgManager;

	// extension point attributes
	public static final String ATTR_NAME = "variableName"; //$NON-NLS-1$
	public static final String ATTR_ARGUMENT_SELECTOR = "argumentSelector"; //$NON-NLS-1$

	/**
	 * Table of configuration elements for variable presentations,
	 * keyed by variable name.
	 */
	private Map<String, IConfigurationElement> fConfigurations;

	/**
	 * Returns the singleton string variable presentation manager.
	 *
	 * @return the singleton string variable presentation manager
	 */
	public static StringVariablePresentationManager getDefault() {
		if (fgManager == null) {
			fgManager = new StringVariablePresentationManager();
		}
		return fgManager;
	}

	/**
	 * Returns an argument selector contributed for the given
	 * variable, or <code>null</code> if none.
	 *
	 * @param variable string substitution variable
	 * @return argument selector or <code>null</code>
	 */
	public IArgumentSelector getArgumentSelector(IStringVariable variable) {
		IConfigurationElement element = fConfigurations.get(variable.getName());
		if (element != null) {
			try {
				return (IArgumentSelector)element.createExecutableExtension(ATTR_ARGUMENT_SELECTOR);
			} catch (CoreException e) {
				DebugUIPlugin.log(e);
			}
		}
		return null;
	}

	/**
	 * Constructs the manager, loading extensions.
	 */
	private StringVariablePresentationManager() {
		initialize();
	}

	/**
	 * Load extensions
	 */
	private void initialize() {
		fConfigurations = new HashMap<>();
		IExtensionPoint point= Platform.getExtensionRegistry().getExtensionPoint(DebugUIPlugin.getUniqueIdentifier(), EXTENSION_POINT_STRING_VARIABLE_PRESENTATIONS);
		IConfigurationElement elements[]= point.getConfigurationElements();
		for (IConfigurationElement element : elements) {
			String name= element.getAttribute(ATTR_NAME);
			if (name == null) {
				DebugUIPlugin.logErrorMessage(MessageFormat.format("String variable presentation extension missing required 'variableName' attribute: {0}", new Object[] { element.getDeclaringExtension().getLabel() })); //$NON-NLS-1$
				continue;
			}
			fConfigurations.put(name, element);
		}
	}


}