/*******************************************************************************
 * Copyright (c) 2015 Zend Technologies and others.
 * 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:
 *     Zend Technologies - initial API and implementation
 *******************************************************************************/
package org.eclipse.php.internal.debug.ui.launching;

import java.util.ArrayList;
import java.util.List;

import org.eclipse.core.runtime.*;
import org.eclipse.php.internal.debug.ui.Logger;
import org.eclipse.php.internal.debug.ui.PHPDebugUIPlugin;

/**
 * Debugger launch settings sections registry.
 * 
 * @author Bartlomiej Laczkowski
 */
public class DebuggerLaunchSettingsSectionRegistry {

	private static List<Entry> entries;

	private class Entry {

		IConfigurationElement element;
		String id;
		String overridenSectionId;
		String debuggerId;
		String launchTypeId;

		public Entry(IConfigurationElement element, String id, String overridenSectionId, String debuggerId,
				String launchTypeId) {
			this.element = element;
			this.id = id;
			this.debuggerId = debuggerId;
			this.launchTypeId = launchTypeId;
			this.overridenSectionId = overridenSectionId;
		}

	}

	private static final String PROP_ID = "id"; //$NON-NLS-1$
	private static final String PROP_OVERRIDES = "overrides"; //$NON-NLS-1$
	private static final String PROP_DEBUGGER_ID = "debuggerId"; //$NON-NLS-1$
	private static final String PROP_LAUNCH_TYPE_ID = "launchTypeId"; //$NON-NLS-1$
	private static final String PROP_SECTION = "section"; //$NON-NLS-1$

	/**
	 * The name of extension point to read settings sections from
	 */
	public static final String EXTENSION_POINT_ID = PHPDebugUIPlugin.getDefault().getBundle().getSymbolicName()
			+ ".phpDebuggerLaunchSettingsSections"; //$NON-NLS-1$

	/**
	 * The default instance for reading registry
	 */
	private static DebuggerLaunchSettingsSectionRegistry instance;

	/**
	 * Returns all loaded entries.
	 */
	private static final List<Entry> getEntries() {
		if (entries == null) {
			entries = getDefault().readFromExtensionPoint();
		}
		return entries;
	}

	/**
	 * Gets settings section by combination of corresponding debugger ID and
	 * launch type ID.
	 * 
	 * @param debuggerId
	 * @param launchTypeId
	 * @return settings section
	 */
	public static final IDebuggerLaunchSettingsSection getSection(String debuggerId, String launchTypeId) {
		for (Entry entry : getEntries()) {
			if (entry.debuggerId.equals(debuggerId) && entry.launchTypeId.equals(launchTypeId)) {
				IDebuggerLaunchSettingsSection settingsSection = null;
				try {
					settingsSection = (IDebuggerLaunchSettingsSection) createInstance(entry.element, PROP_SECTION,
							IDebuggerLaunchSettingsSection.class);
				} catch (CoreException e) {
					Logger.logException(
							"Could not instantiate debugger launch settings section from extension point data.", //$NON-NLS-1$
							e);
				}
				return settingsSection;
			}
		}
		return null;
	}

	private static DebuggerLaunchSettingsSectionRegistry getDefault() {
		if (instance == null) {
			instance = new DebuggerLaunchSettingsSectionRegistry();
		}
		return instance;
	}

	private List<Entry> readFromExtensionPoint() {
		final List<Entry> entries = new ArrayList<Entry>();
		IConfigurationElement[] configurationElements = Platform.getExtensionRegistry()
				.getConfigurationElementsFor(EXTENSION_POINT_ID);
		for (final IConfigurationElement element : configurationElements) {
			String id = element.getAttribute(PROP_ID);
			String overridenSectionId = element.getAttribute(PROP_OVERRIDES);
			String debuggerId = element.getAttribute(PROP_DEBUGGER_ID);
			String launchTypeId = element.getAttribute(PROP_LAUNCH_TYPE_ID);
			entries.add(new Entry(element, id, overridenSectionId, debuggerId, launchTypeId));
		}
		return filterEntries(entries);
	}

	@SuppressWarnings({ "unchecked", "rawtypes" })
	private static Object createInstance(IConfigurationElement element, String propertyName, Class instanceClass)
			throws CoreException {
		final Object object = element.createExecutableExtension(propertyName);
		if (!instanceClass.isAssignableFrom(object.getClass())) {
			String message = String.format("Invalid typecast for %s", //$NON-NLS-1$
					element.getAttribute(propertyName));
			IStatus status = new Status(IStatus.ERROR, PHPDebugUIPlugin.getDefault().getBundle().getSymbolicName(),
					message);
			throw new CoreException(status);
		}
		return object;
	}

	private List<Entry> filterEntries(List<Entry> entries) {
		List<Entry> topHierarchyEntries = new ArrayList<Entry>();
		for (Entry entryToCheck : entries) {
			boolean isTopHierarchy = true;
			for (Entry entry : entries) {
				if (entryToCheck.id.equals(entry.overridenSectionId)) {
					isTopHierarchy = false;
					break;
				}
			}
			if (isTopHierarchy)
				topHierarchyEntries.add(entryToCheck);
		}
		return topHierarchyEntries;
	}

}