/*******************************************************************************
 * Copyright (c) 2006, 2015 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.ui;

import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;
import org.eclipse.core.runtime.IAdaptable;
import org.eclipse.core.runtime.IAdapterManager;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExecutableExtension;
import org.eclipse.core.runtime.Platform;
import org.eclipse.ui.internal.WorkbenchPlugin;
import org.osgi.framework.Bundle;
import org.osgi.service.packageadmin.ExportedPackage;
import org.osgi.service.packageadmin.PackageAdmin;
import org.osgi.util.tracker.ServiceTracker;

/**
 * Basic IWorkingSetElementAdapter implementation that allows plugins to
 * describe simple declarative element adapters.
 * <p>
 * The executable extension format for this class is as follows:<br>
 * </p>
 *
 * <pre>
 * <code>&lt;workingSet elementAdapterClass="org.eclipse.ui.BasicWorkingSetElementAdapter:class1.to.adapt.to[;option1=value1][;option2=value2],class2.to.adapt.to[;option1=value1][;option2=value2],..."&gt;
 * ...
 * &lt;/workingSet&gt;</code>
 * </pre>
 * <p>
 * The valid options are:<br>
 * </p>
 * <dl>
 * <dt>adapt</dt>
 * <dd>Values: <code>true</code> or <code>true</code>. Specifies whether or not
 * the platform {@link org.eclipse.core.runtime.IAdapterManager} and the
 * {@link org.eclipse.core.runtime.IAdaptable} interface should be
 * consulted.</dd>
 * </dl>
 *
 * Please see the {@link #adaptElements(IWorkingSet, IAdaptable[])} method for
 * details on behavior of this implementation.
 *
 * @since 3.3
 */
public final class BasicWorkingSetElementAdapter implements IWorkingSetElementAdapter, IExecutableExtension {

	private static class Type {
		private static final int NONE = 0;
		private static final int ADAPT = 1;
		String className;
		int flags;
	}

	private Type[] preferredTypes = new Type[0];

	private ServiceTracker<?, ?> packageTracker;

	/**
	 * When invoked this method will iterate over all classes specified as
	 * IExecutableExtension arguements to this class in order and compare with the
	 * elements. If the element is directly assignable to the provided class then it
	 * is added to the result array as is. If the class has specified "adapt=true"
	 * as an argument and there is an available adapter in the platform
	 * IAdapterManager then it is returned. Finally, if "adapt=true" and the class
	 * is already loaded (determined by inspecting exported bundles via the platform
	 * PackageAdmin) a direct query for the adapter is made on the object and if it
	 * is not <code>null</code> then it is returned.
	 * <p>
	 * A consequence of the above is that it is possible for this method to return
	 * differing results based on the state of bundles loaded within the system.
	 * </p>
	 *
	 * @see org.eclipse.ui.IWorkingSetElementAdapter#adaptElements(org.eclipse.ui.IWorkingSet,
	 *      org.eclipse.core.runtime.IAdaptable[])
	 * @see org.eclipse.core.runtime.IAdapterManager#getAdapter(Object, String)
	 * @see org.osgi.service.packageadmin.PackageAdmin#getExportedPackage(String)
	 */
	@Override
	public IAdaptable[] adaptElements(IWorkingSet ws, IAdaptable[] elements) {
		List<IAdaptable> adaptedElements = new ArrayList<>();
		for (IAdaptable element : elements) {
			IAdaptable adaptable = adapt(element);
			if (adaptable != null)
				adaptedElements.add(adaptable);
		}

		return adaptedElements.toArray(new IAdaptable[adaptedElements.size()]);
	}

	/**
	 * Adapt the given adaptable. Compares the given adaptable against the list of
	 * desired types and returns the first type that generates a match.
	 *
	 * @param adaptable the adaptable to adapt
	 * @return the resultant adaptable. May be the same adaptable, a new adaptable,
	 *         or <code>null</code>.
	 */
	private IAdaptable adapt(IAdaptable adaptable) {
		for (Type preferredType : preferredTypes) {
			IAdaptable adaptedAdaptable = adapt(preferredType, adaptable);
			if (adaptedAdaptable != null)
				return adaptedAdaptable;
		}
		return null;
	}

	/**
	 * Adapt the given adaptable given the reference type.
	 *
	 * @param type      the reference type
	 * @param adaptable the adaptable to adapt
	 * @return the resultant adaptable. May be the same adaptable, a new adaptable,
	 *         or <code>null</code>.
	 */
	private IAdaptable adapt(Type type, IAdaptable adaptable) {
		IAdapterManager adapterManager = Platform.getAdapterManager();
		Class<?>[] directClasses = adapterManager.computeClassOrder(adaptable.getClass());
		for (Class<?> clazz : directClasses) {
			if (clazz.getName().equals(type.className))
				return adaptable;
		}

		if ((type.flags & Type.ADAPT) != 0) {
			Object adapted = adapterManager.getAdapter(adaptable, type.className);
			if (adapted instanceof IAdaptable)
				return (IAdaptable) adapted;

			PackageAdmin admin = getPackageAdmin();
			if (admin != null) {
				int lastDot = type.className.lastIndexOf('.');
				if (lastDot > 0) { // this lives in a package
					String packageName = type.className.substring(0, lastDot);
					ExportedPackage[] packages = admin.getExportedPackages(packageName);
					if (packages != null && packages.length == 1) {
						// if there is exactly one exporter of this
						// package
						// we can go further
						if (packages[0].getExportingBundle().getState() == Bundle.ACTIVE) {
							try {
								// if the bundle is loaded we can safely get the
								// class object and check for an adapter on the
								// object directly
								adapted = adaptable
										.getAdapter(packages[0].getExportingBundle().loadClass(type.className));
								if (adapted instanceof IAdaptable)
									return (IAdaptable) adapted;

							} catch (ClassNotFoundException e) {
								WorkbenchPlugin.log(e);
							}
						}
					}
				}
			}
		}
		return null;
	}

	@Override
	public void dispose() {
		if (packageTracker != null)
			packageTracker.close();
	}

	@Override
	public void setInitializationData(IConfigurationElement config, String propertyName, Object data) {

		if (data instanceof String) {
			List<Type> preferredTypes = new ArrayList<>(0);
			for (StringTokenizer toker = new StringTokenizer((String) data, ","); toker.hasMoreTokens();) {//$NON-NLS-1$
				String classNameAndOptions = toker.nextToken();
				Type record = new Type();
				parseOptions(classNameAndOptions, record);
				preferredTypes.add(record);
			}
			this.preferredTypes = preferredTypes.toArray(new Type[preferredTypes.size()]);
		}
	}

	/**
	 * Parse classname/option strings in the form:<br>
	 * <code>some.package.Class[:option1=value1][:option2=value2]...</code>
	 *
	 * @param classNameAndOptions the class name and possibly options to parse
	 * @param record              the record to fill
	 */
	private void parseOptions(String classNameAndOptions, Type record) {
		for (StringTokenizer toker = new StringTokenizer(classNameAndOptions, ";"); toker.hasMoreTokens();) { //$NON-NLS-1$
			String token = toker.nextToken();
			if (record.className == null)
				record.className = token;
			else {
				for (StringTokenizer pair = new StringTokenizer(token, "="); pair.hasMoreTokens();) {//$NON-NLS-1$
					if (pair.countTokens() == 2) {
						String param = pair.nextToken();
						String value = pair.nextToken();
						if ("adapt".equals(param)) { //$NON-NLS-1$
							record.flags ^= "true".equals(value) ? Type.ADAPT : Type.NONE; //$NON-NLS-1$
						}
					}
				}
			}
		}
	}

	/**
	 * Prime the PackageAdmin service tracker and return the service (if available).
	 *
	 * @return the PackageAdmin service or null if it is not available
	 */
	private PackageAdmin getPackageAdmin() {
		if (packageTracker == null) {
			packageTracker = new ServiceTracker<>(WorkbenchPlugin.getDefault().getBundleContext(),
					PackageAdmin.class.getName(), null);
			packageTracker.open();
		}

		return (PackageAdmin) packageTracker.getService();
	}
}