EDIT

/*******************************************************************************

 * Copyright (c) 2014 OPCoach.

 * 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:

 *     OPCoach - initial API and implementation

 *******************************************************************************/

package com.opcoach.e4.preferences;

import java.util.ArrayList;

import java.util.Collection;

import java.util.Collections;

import java.util.HashMap;

import java.util.Map;

import javax.inject.Inject;

import org.eclipse.core.runtime.IConfigurationElement;

import org.eclipse.core.runtime.IExtensionRegistry;

import org.eclipse.core.runtime.preferences.InstanceScope;

import org.eclipse.e4.core.contexts.ContextInjectionFactory;

import org.eclipse.e4.core.contexts.IEclipseContext;

import org.eclipse.e4.core.di.annotations.Creatable;

import org.eclipse.e4.core.services.contributions.IContributionFactory;

import org.eclipse.e4.core.services.log.Logger;

import org.eclipse.jface.preference.IPreferenceNode;

import org.eclipse.jface.preference.IPreferenceStore;

import org.eclipse.jface.preference.PreferenceManager;

import org.eclipse.jface.preference.PreferenceNode;

import org.eclipse.jface.preference.PreferencePage;

import org.eclipse.swt.SWT;

import org.eclipse.swt.widgets.Composite;

import org.eclipse.swt.widgets.Control;

import org.eclipse.swt.widgets.Label;

@Creatable

public class E4PreferenceRegistry

{

	public static final String PREFS_PAGE_XP = "eu.etaxonomy.taxeditor.workbench.e4PreferencePages"; // $NON-NLS-1$

	public static final String PREF_STORE_PROVIDER = "eu.etaxonomy.taxeditor.workbench.e4PreferenceStoreProvider"; // $NON-NLS-1$

	protected static final String ELMT_PAGE = "page"; // $NON-NLS-1$

	protected static final String ATTR_ID = "id"; // $NON-NLS-1$

	protected static final String ATTR_CATEGORY = "category"; // $NON-NLS-1$

	protected static final String ATTR_CLASS = "class"; // $NON-NLS-1$

	protected static final String ATTR_NAME = "name"; // $NON-NLS-1$

	protected static final String ATTR_PLUGIN_ID = "pluginId"; // $NON-NLS-1$

	protected static final String ATTR_ID_IN_WBCONTEXT = "idInWorkbenchContext"; // $NON-NLS-1$

	@Inject

	protected Logger logger;

	@Inject

	protected IEclipseContext context;

	@Inject

	protected IExtensionRegistry registry;

	private PreferenceManager pm = null;

	// A map of (pluginId, { IPreferenceStoreProvider, or key in wbcontext }

	private Map<String, Object> psProviders;

	public PreferenceManager getPreferenceManager()

	{

		// Remember of the unbounded nodes to order parent pages.

		// Map<category, list of children> (all nodes except root nodes)

		Map<String, Collection<IPreferenceNode>> childrenNodes = new HashMap<String, Collection<IPreferenceNode>>();

		if (pm != null) {

            return pm;

        }

		pm = new PreferenceManager();

		IContributionFactory factory = context.get(IContributionFactory.class);

		for (IConfigurationElement elmt : registry.getConfigurationElementsFor(PREFS_PAGE_XP))

		{

			String bundleId = elmt.getNamespaceIdentifier();

			if (!elmt.getName().equals(ELMT_PAGE))

			{

				logger.warn("unexpected element: {0}", elmt.getName());

				continue;

			} else if (isEmpty(elmt.getAttribute(ATTR_ID)) || isEmpty(elmt.getAttribute(ATTR_NAME)))

			{

				logger.warn("missing id and/or name: {}", bundleId);

				continue;

			}

			PreferenceNode pn = null;

			if (elmt.getAttribute(ATTR_CLASS) != null)

			{

				PreferencePage page = null;

				try

				{

					String prefPageURI = getClassURI(bundleId, elmt.getAttribute(ATTR_CLASS));

					Object object = factory.create(prefPageURI, context);

					if (!(object instanceof PreferencePage))

					{

						logger.error("Expected instance of PreferencePage: {0}", elmt.getAttribute(ATTR_CLASS));

						continue;

					}

					page = (PreferencePage) object;

					setPreferenceStore(bundleId, page);

				} catch (ClassNotFoundException e)

				{

					logger.error(e);

					continue;

				}

				ContextInjectionFactory.inject(page, context);

				if ((page.getTitle() == null || page.getTitle().isEmpty()) && elmt.getAttribute(ATTR_NAME) != null)

				{

					page.setTitle(elmt.getAttribute(ATTR_NAME));

				}

				pn = new PreferenceNode(elmt.getAttribute(ATTR_ID), page);

			} else

			{

				pn = new PreferenceNode(elmt.getAttribute(ATTR_ID), new EmptyPreferencePage(elmt.getAttribute(ATTR_NAME)));

			}

			// Issue 2 : Fix bug on order (see :

			// https://github.com/opcoach/e4Preferences/issues/2)

			// Add only pages at root level and remember of child pages for

			// categories

			String category = elmt.getAttribute(ATTR_CATEGORY);

			if (isEmpty(category))

			{

				pm.addToRoot(pn);

			} else

			{

				/*

				 * IPreferenceNode parent = findNode(pm, category); if (parent

				 * == null) { // No parent found, but may be the extension has

				 * not been read yet. So remember of it unboundedNodes.put(pn,

				 * category); } else { parent.add(pn); }

				 */

				// Check if this category is already registered.

				Collection<IPreferenceNode> children = childrenNodes.get(category);

				if (children == null)

				{

					children = new ArrayList<IPreferenceNode>();

					childrenNodes.put(category, children);

				}

				children.add(pn);

			}

		}

		// Must now bind pages that has not been added in nodes (depends on the

		// preference page read order)

		// Iterate on all possible categories

		Collection<String> categoriesDone = new ArrayList<String>();

		while (!childrenNodes.isEmpty())

		{

			for (String cat : Collections.unmodifiableSet(childrenNodes.keySet()))

			{

				// Is this category already in preference manager ? If not add

				// it later...

				IPreferenceNode parent = findNode(pm, cat);

				if (parent != null)

				{

					// Can add the list of children to this parent page...

					for (IPreferenceNode pn : childrenNodes.get(cat))

					{

						parent.add(pn);

					}

					// Ok This parent page is done. Can remove it from map

					// outside of this loop

					categoriesDone.add(cat);

				}

			}

			for (String keyToRemove : categoriesDone) {

                childrenNodes.remove(keyToRemove);

            }

			categoriesDone.clear();

		}

		return pm;

	}

	private void setPreferenceStore(String bundleId, PreferencePage page)

	{

		// Affect preference store to this page if this is a

		// PreferencePage, else, must manage it internally

		// Set the issue#1 on github :

		// https://github.com/opcoach/e4Preferences/issues/1

		// And manage the extensions of IP

		initialisePreferenceStoreProviders();

		IPreferenceStore store = null;

		// Get the preference store according to policy.

		Object data = psProviders.get(bundleId);

		if (data != null)

		{

			if (data instanceof IPreferenceStore) {

                store = (IPreferenceStore) data;

            } else if (data instanceof IPreferenceStoreProvider) {

                store = ((IPreferenceStoreProvider) data).getPreferenceStore();

            } else if (data instanceof String) {

                store = (IPreferenceStore) context.get((String) data);

            }

		} else

		{

			// Default behavior : create a preference store for this bundle and remember of it

			store = new ScopedPreferenceStore(InstanceScope.INSTANCE, bundleId);

			psProviders.put(bundleId, store);

		}

		if (store != null) {

            page.setPreferenceStore(store);

        } else

		{

			logger.warn("Unable to set the preferenceStore for page " + page.getTitle() + " defined in bundle " + bundleId);

		}

	}

	/** Read the e4PreferenceStoreProvider extension point */

	private void initialisePreferenceStoreProviders()

	{

		if (psProviders == null)

		{

			IContributionFactory factory = context.get(IContributionFactory.class);

			psProviders = new HashMap<String, Object>();

			// Read extensions and fill the map...

			for (IConfigurationElement elmt : registry.getConfigurationElementsFor(PREF_STORE_PROVIDER))

			{

				String declaringBundle = elmt.getNamespaceIdentifier();

				String pluginId = elmt.getAttribute(ATTR_PLUGIN_ID);

				if (isEmpty(pluginId))

				{

					logger.warn("missing plugin Id in extension " + PREF_STORE_PROVIDER + " check the plugin " + declaringBundle);

					continue;

				}

				String classname = elmt.getAttribute(ATTR_CLASS);

				String objectId = elmt.getAttribute(ATTR_ID_IN_WBCONTEXT);

				if ((isEmpty(classname) && isEmpty(objectId)) || (((classname != null) && classname.length() > 0) && ((objectId != null) && objectId.length() > 0)))

				{

					logger.warn("In extension " + PREF_STORE_PROVIDER + " only one of the two attributes (pluginId or idInWorkbenchContext) must be set. Check the plugin "

							+ declaringBundle);

					continue;

				}

				// Ok can now work with data...

				Object data = objectId;

				if (classname != null)

				{

					data = factory.create(classname, context);

					if (!(data instanceof IPreferenceStoreProvider))

					{

						logger.warn("In extension " + PREF_STORE_PROVIDER + " the class must implements IPreferenceStoreProvider. Check the plugin " + declaringBundle);

						continue;

					}

				}

				psProviders.put(pluginId, data);

			}

		}

	}

	private IPreferenceNode findNode(PreferenceManager pm, String categoryId)

	{

		for (Object o : pm.getElements(PreferenceManager.POST_ORDER))

		{

			if (o instanceof IPreferenceNode && ((IPreferenceNode) o).getId().equals(categoryId))

			{

				return (IPreferenceNode) o;

			}

		}

		return null;

	}

	private String getClassURI(String definingBundleId, String spec) throws ClassNotFoundException

	{

		if (spec.startsWith("platform:"))

		{

			return spec;

		} // $NON-NLS-1$

		return "bundleclass://" + definingBundleId + '/' + spec;

	}

	private boolean isEmpty(String value)

	{

		return value == null || value.trim().isEmpty();

	}

	static class EmptyPreferencePage extends PreferencePage

	{

		public EmptyPreferencePage(String title)

		{

			setTitle(title);

			noDefaultAndApplyButton();

		}

		@Override

		protected Control createContents(Composite parent)

		{

			return new Label(parent, SWT.NONE);

		}

	}

}