com.google.dart.tools.search2.internal.ui.text2.TextSearchQueryProviderRegistry.java Source code

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Here is the source code for com.google.dart.tools.search2.internal.ui.text2.TextSearchQueryProviderRegistry.java

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/*
 * Copyright (c) 2012, the Dart project authors.
 * 
 * Licensed under the Eclipse Public License v1.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 * 
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.dart.tools.search2.internal.ui.text2;

import com.google.dart.tools.search.internal.ui.SearchPlugin;
import com.google.dart.tools.search.internal.ui.SearchPreferencePage;
import com.google.dart.tools.search.ui.text.TextSearchQueryProvider;
import com.google.dart.tools.search2.internal.ui.SearchMessages;

import java.util.ArrayList;

import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.Platform;

import org.eclipse.jface.preference.IPreferenceStore;
import org.eclipse.jface.util.SafeRunnable;

public class TextSearchQueryProviderRegistry {

    private static final String EXTENSION_POINT_ID = "com.google.dart.tools.search.textSearchQueryProvider"; //$NON-NLS-1$
    private static final String PROVIDER_NODE_NAME = "textSearchQueryProvider"; //$NON-NLS-1$
    private static final String ATTRIB_ID = "id"; //$NON-NLS-1$
    private static final String ATTRIB_LABEL = "label"; //$NON-NLS-1$
    private static final String ATTRIB_CLASS = "class"; //$NON-NLS-1$

    private TextSearchQueryProvider fPreferredProvider;
    private String fPreferredProviderId;

    public TextSearchQueryProviderRegistry() {
        fPreferredProviderId = null; // only null when not initialized
        fPreferredProvider = null;
    }

    public TextSearchQueryProvider getPreferred() {
        String preferredId = getPreferredEngineID();
        if (!preferredId.equals(fPreferredProviderId)) {
            updateProvider(preferredId);
        }
        return fPreferredProvider;
    }

    private void updateProvider(String preferredId) {
        fPreferredProviderId = preferredId;
        fPreferredProvider = null;
        if (preferredId.length() != 0) { // empty string: default engine
            fPreferredProvider = createFromExtension(preferredId);
        }
        if (fPreferredProvider == null) {
            fPreferredProvider = new DefaultTextSearchQueryProvider();
        }
    }

    private String getPreferredEngineID() {
        IPreferenceStore prefs = SearchPlugin.getDefault().getPreferenceStore();
        String preferedEngine = prefs.getString(SearchPreferencePage.TEXT_SEARCH_QUERY_PROVIDER);
        return preferedEngine;
    }

    private TextSearchQueryProvider createFromExtension(final String id) {
        final TextSearchQueryProvider[] res = new TextSearchQueryProvider[] { null };

        SafeRunnable safe = new SafeRunnable() {
            public void run() throws Exception {
                IConfigurationElement[] extensions = Platform.getExtensionRegistry()
                        .getConfigurationElementsFor(EXTENSION_POINT_ID);
                for (int i = 0; i < extensions.length; i++) {
                    IConfigurationElement curr = extensions[i];
                    if (PROVIDER_NODE_NAME.equals(curr.getName()) && id.equals(curr.getAttribute(ATTRIB_ID))) {
                        res[0] = (TextSearchQueryProvider) curr.createExecutableExtension(ATTRIB_CLASS);
                        return;
                    }
                }
            }

            public void handleException(Throwable e) {
                SearchPlugin.log(e);
            }
        };
        SafeRunnable.run(safe);
        return res[0];
    }

    public String[][] getAvailableProviders() {
        ArrayList<String[]> res = new ArrayList<String[]>();
        res.add(new String[] { SearchMessages.TextSearchQueryProviderRegistry_defaultProviderLabel, "" }); //$NON-NLS-1$

        IConfigurationElement[] extensions = Platform.getExtensionRegistry()
                .getConfigurationElementsFor(EXTENSION_POINT_ID);
        for (int i = 0; i < extensions.length; i++) {
            IConfigurationElement engine = extensions[i];
            if (PROVIDER_NODE_NAME.equals(engine.getName())) {
                res.add(new String[] { engine.getAttribute(ATTRIB_LABEL), engine.getAttribute(ATTRIB_ID) });
            }
        }
        return res.toArray(new String[res.size()][]);
    }
}