/*******************************************************************************
 * Copyright (c) 2007, 2010 Association for Decentralized Information Management
 * in Industry THTH ry.
 * 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:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
package org.simantics.browsing.ui.common.extension;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtension;
import org.eclipse.core.runtime.IExtensionPoint;
import org.eclipse.core.runtime.Platform;
import org.eclipse.core.runtime.dynamichelpers.ExtensionTracker;
import org.eclipse.core.runtime.dynamichelpers.IExtensionChangeHandler;
import org.eclipse.core.runtime.dynamichelpers.IExtensionTracker;
import org.eclipse.core.runtime.dynamichelpers.IFilter;
import org.simantics.browsing.ui.common.Activator;
import org.simantics.browsing.ui.common.extension.internal.ContributorBindingExtension;
import org.simantics.browsing.ui.common.extension.internal.ContributorImplementationBinding;
import org.simantics.browsing.ui.common.extension.internal.ContributorReferenceBinding;
import org.simantics.browsing.ui.content.Contributor;
import org.simantics.browsing.ui.content.ContributorBinding;
import org.simantics.scl.reflection.OntologyVersions;
import org.simantics.utils.strings.StringUtils;

/**
 * @author Antti Villberg
 */
public abstract class ContributorBindingExtensionManager<Factory> implements IExtensionChangeHandler {

    private final static String                    NAMESPACE  = Activator.PLUGIN_ID;

    private ExtensionTracker                       tracker;

    private static final OntologyVersions VERSIONS = OntologyVersions.getInstance();
    
    @SuppressWarnings("unchecked")
    private ContributorBindingExtension<Factory>[] extensions = new ContributorBindingExtension[0];

    abstract String getExtensionPointName();

    ContributorBindingExtensionManager() {
        tracker = new ExtensionTracker();

        // Cache defined actions
        IExtensionPoint expt = Platform.getExtensionRegistry().getExtensionPoint(NAMESPACE, getExtensionPointName());
        loadExtensions(expt.getConfigurationElements());

        // Start tracking for new and removed extensions
        IFilter filter = ExtensionTracker.createExtensionPointFilter(expt);
        tracker.registerHandler(this, filter);
    }

    @SuppressWarnings("unchecked")
    void close() {
        tracker.close();
        tracker = null;
        extensions = new ContributorBindingExtension[0];
    }

    public ContributorBindingExtension<Factory>[] getExtensions() {
        return extensions;
    }

    abstract ContributorReferenceBinding<Factory> createReferenceBinding(double preference, String browseContext, String factoryId);

    @SuppressWarnings("unchecked")
    private void loadExtensions(IConfigurationElement[] elements) {

        Set<ContributorBindingExtension<Factory>> newExtensions = new HashSet<ContributorBindingExtension<Factory>>(Arrays.asList(extensions));

        for (IConfigurationElement el : elements) {

            String browseContext = VERSIONS.currentVersion(StringUtils.safeString(el.getAttribute("browseContext")));

            for(IConfigurationElement child : el.getChildren("reference")) {

                double preference = StringUtils.safeDouble(child.getAttribute("preference"));
                String factoryId = StringUtils.safeString(child.getAttribute("id"));
//                ContributionBindingExtension<Factory> ext = new ImagerContributionReferenceBinding(preference, browseContext, factoryId);
                ContributorBindingExtension<Factory> ext = createReferenceBinding(preference, browseContext, factoryId);

                // Start tracking the new extension object, its removal will be notified of
                // with removeExtension(extension, Object[]).
                tracker.registerObject(el.getDeclaringExtension(), ext, IExtensionTracker.REF_STRONG);

                newExtensions.add(ext);

            }

            for(IConfigurationElement child : el.getChildren("implementation")) {

                double preference = StringUtils.safeDouble(child.getAttribute("preference"));

                try {

                    Contributor<Factory> factory = (Contributor<Factory>) child.createExecutableExtension("class");
                    ContributorBindingExtension<Factory> ext = new ContributorImplementationBinding<Factory>(preference, browseContext, factory);

                    // Start tracking the new extension object, its removal will be notified of
                    // with removeExtension(extension, Object[]).
                    tracker.registerObject(el.getDeclaringExtension(), ext, IExtensionTracker.REF_STRONG);

                    newExtensions.add(ext);

                } catch (CoreException e) {

                    System.out.println(" == Could not load ViewpointContributionFactory '" + child.getAttribute("class") + "' due to the following error: " + e.getMessage()  );
	                
                }

            }

        }

        // Atomic assignment
        this.extensions = newExtensions.toArray(new ContributorBindingExtension[newExtensions.size()]);
    }

    @Override
    public void addExtension(IExtensionTracker tracker, IExtension extension) {
        loadExtensions(extension.getConfigurationElements());
    }

    @SuppressWarnings("unchecked")
    @Override
    public void removeExtension(IExtension extension, Object[] objects) {
        Set<ContributorBindingExtension<Factory>> newExtensions = new HashSet<ContributorBindingExtension<Factory>>(Arrays.asList(extensions));

        for (Object o : objects) {
            tracker.unregisterObject(extension, o);
            newExtensions.remove(o);
        }

        // Atomic assignment
        this.extensions = newExtensions.toArray(new ContributorBindingExtension[newExtensions.size()]);
    }

    public Set<ContributorBinding<Factory>> getBoundContributions(Set<String> browseContexts) {

        HashSet<ContributorBinding<Factory>> result = new HashSet<ContributorBinding<Factory>>();

        for(ContributorBindingExtension<Factory> binding : getExtensions()) {
            if(browseContexts.contains(binding.getBrowseContext())) {
                Contributor<Factory> factory = binding.getFactory();
                if(factory != null) {
//                    System.out.println("----------- Plugin contribution " + binding.getFactory() + " " + binding.getPreference());
                    result.add(new ContributorBindingImpl<Factory>(binding.getPreference(), factory));
                } else {
//                    System.out.println("FAILED: ----------- No factory for " + binding);
                }

            }
        }

        return result;

    }

}