/*******************************************************************************
 * Copyright (c) 2015 Red Hat Inc.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Mickael Istria (Red Hat Inc.) - initial API and implementation
 *******************************************************************************/
package org.eclipse.ui.internal.ide.registry;

import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.Platform;
import org.eclipse.ui.ide.IUnassociatedEditorStrategy;
import org.eclipse.ui.internal.ide.IDEWorkbenchPlugin;

/**
 * @since 3.12
 *
 */
public class UnassociatedEditorStrategyRegistry {

	private static final String EXTENSION_POINT_ID = IDEWorkbenchPlugin.IDE_WORKBENCH + ".unassociatedEditorStrategy"; //$NON-NLS-1$

	private static Map<String, String> idsToLabel;

	/**
	 * @param strategyId
	 *            The strategy to look for
	 * @return an instance of the strategy, or {@code null} if no strategy is
	 *         found for this id
	 */
	public IUnassociatedEditorStrategy getStrategy(String strategyId) {
		if (strategyId == null) {
			return null;
		}
		IExtensionRegistry extRegistry = Platform.getExtensionRegistry();
		IConfigurationElement[] extensions = extRegistry.getConfigurationElementsFor(EXTENSION_POINT_ID);
		if (extensions != null) {
			for (IConfigurationElement extension : extensions) {
				if (strategyId.equals(readAttribute(extension, "id"))) { //$NON-NLS-1$
					try {
						return (IUnassociatedEditorStrategy) extension.createExecutableExtension("class"); //$NON-NLS-1$
					} catch (CoreException ex) {
						IDEWorkbenchPlugin.log(ex.getMessage(), ex);
						return null;
					}
				}
			}
		}
		return null;
	}

	private String readAttribute(IConfigurationElement extension, String attribute) {
		String res = extension.getAttribute(attribute);
		if (res == null) {
			IDEWorkbenchPlugin.log("Missing attribute '" + attribute + "' for extension to " + EXTENSION_POINT_ID //$NON-NLS-1$ //$NON-NLS-2$
					+ " contributed by " + extension.getContributor()); //$NON-NLS-1$
		}
		return res;
	}

	/**
	 * Reads the known strategies from registry
	 *
	 * @return not modifiable set with all known strategy id's in their
	 *         definition order
	 */
	public Set<String> retrieveAllStrategies() {
		populateIdsToLabel();
		return Collections.unmodifiableSet(idsToLabel.keySet());
	}

	/**
	 * @param id
	 *            the id of the strategy to use
	 * @return the label for the supplied strategy id, or {@code null} for
	 *         unknown id.
	 */
	public String getLabel(String id) {
		if (idsToLabel == null || !idsToLabel.containsKey(id)) {
			populateIdsToLabel();
		}
		return idsToLabel.get(id);
	}

	private void populateIdsToLabel() {
		Map<String, String> res = new LinkedHashMap<>();
		IExtensionRegistry extRegistry = Platform.getExtensionRegistry();
		IConfigurationElement[] extensions = extRegistry.getConfigurationElementsFor(EXTENSION_POINT_ID);
		if (extensions != null) {
			for (IConfigurationElement extension : extensions) {
				String extId = readAttribute(extension, "id"); //$NON-NLS-1$
				String label = readAttribute(extension, "label"); //$NON-NLS-1$
				if (extId != null && label != null) {
					res.put(extId, label);
				}
			}
		}
		idsToLabel = res;
	}

	/**
	 * @param strategyId
	 * @return Whether the specified strategy is interactive, or false is
	 *         strategy is unknown
	 */
	public boolean isInteractive(String strategyId) {
		if (strategyId == null) {
			return false;
		}
		IExtensionRegistry extRegistry = Platform.getExtensionRegistry();
		IConfigurationElement[] extensions = extRegistry.getConfigurationElementsFor(EXTENSION_POINT_ID);
		if (extensions != null) {
			for (IConfigurationElement extension : extensions) {
				if (strategyId.equals(readAttribute(extension, "id"))) { //$NON-NLS-1$
					return Boolean.parseBoolean(readAttribute(extension, "interactive")); //$NON-NLS-1$
				}
			}
		}
		IDEWorkbenchPlugin.log("No editor strategy found for " + strategyId); //$NON-NLS-1$
		return false;
	}

}