<change id="ProjectProblemsProviderSupport">

            <api name="general"/>

            <summary>Added a support class for ProjectProblemsProvider.</summary>

            <version major="1" minor="63"/>

            <date day="2" month="10" year="2012"/>

            <author login="tmysik"/>

            <compatibility addition="yes"/>

            <description>

                <p>

                    Added support class for provider of project metadata problems.

                </p>

            </description>

            <class package="org.netbeans.api.project.ui.support" name="ProjectProblemsProviderSupport"/>

            <issue number="219313"/>

        </change>

 * @see org.netbeans.spi.project.ui.support.ProjectProblemsProviderSupport

 *

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package org.netbeans.spi.project.ui.support;

import java.beans.PropertyChangeListener;

import java.beans.PropertyChangeSupport;

import java.util.ArrayList;

import java.util.Collection;

import java.util.Collections;

import org.netbeans.api.annotations.common.NonNull;

import org.netbeans.spi.project.ui.ProjectProblemsProvider;

import org.openide.util.Parameters;

/**

 * Support for {@link ProjectProblemsProvider provider of project metadata problems}.

 * <p>

 * This class is thread-safe.

 * @author Tomas Mysik

 * @since 1.63

 */

public final class ProjectProblemsProviderSupport {

    private final PropertyChangeSupport propertyChangeSupport;

    private final Object problemsLock = new Object();

    // @GuardedBy("problemsLock")

    private Collection<ProjectProblemsProvider.ProjectProblem> problems;

    // @GuardedBy("problemsLock")

    private long changeId;

    /**

     * Create a new {@code ProjectProblemsProviderSupport}.

     *

     * @param source an instance to be given as the source for events, never {@code null}

     */

    public ProjectProblemsProviderSupport(@NonNull Object source) {

        Parameters.notNull("source", source);

        propertyChangeSupport = new PropertyChangeSupport(source);

    }

    /**

     * Add a listener to the listener list.

     * @param listener {@link PropertyChangeListener} to be added, never {@code null}

     * @see PropertyChangeSupport#addPropertyChangeListener(PropertyChangeListener)

     */

    public void addPropertyChangeListener(@NonNull PropertyChangeListener listener) {

        Parameters.notNull("listener", listener);

        propertyChangeSupport.addPropertyChangeListener(listener);

    }

    /**

     * Remove a listener from the listener list.

     * @param listener {@link PropertyChangeListener} to be removed, never {@code null}

     * @see PropertyChangeSupport#removePropertyChangeListener(PropertyChangeListener)

     */

    public void removePropertyChangeListener(@NonNull PropertyChangeListener listener) {

        Parameters.notNull("listener", listener);

        propertyChangeSupport.removePropertyChangeListener(listener);

    }

    /**

     * Get project problems using the given {@link ProblemsCollector problems collector}.

     * @param problemsCollector {@link ProblemsCollector problems collector} to be used, never {@code null}

     * @return collection of project problems, never {@code null}

     */

    @NonNull

    public Collection<? extends ProjectProblemsProvider.ProjectProblem> getProblems(@NonNull ProblemsCollector problemsCollector) {

        Parameters.notNull("problemsCollector", problemsCollector);

        Collection<ProjectProblemsProvider.ProjectProblem> currentProblems;

        long currentChangeId;

        synchronized (problemsLock) {

            currentProblems = problems;

            currentChangeId = changeId;

        }

        if (currentProblems != null) {

            return Collections.unmodifiableCollection(currentProblems);

        }

        currentProblems = new ArrayList<ProjectProblemsProvider.ProjectProblem>();

        currentProblems.addAll(problemsCollector.collectProblems());

        if (currentProblems.isEmpty()) {

            currentProblems = Collections.<ProjectProblemsProvider.ProjectProblem>emptySet();

        }

        synchronized (problemsLock) {

            if (currentChangeId == changeId) {

                problems = currentProblems;

            } else if (problems != null) {

                currentProblems = problems;

            }

        }

        assert currentProblems != null;

        return Collections.unmodifiableCollection(currentProblems);

    }

    /**

     * Fire {@link ProjectProblemsProvider#PROP_PROBLEMS project problems property} change event to all registered listeners.

     */

    public void fireProblemsChange() {

        synchronized (problemsLock) {

            problems = null;

            changeId++;

        }

        propertyChangeSupport.firePropertyChange(ProjectProblemsProvider.PROP_PROBLEMS, null, null);

    }

    //~ Inner classes

    /**

     * Collector of current project problems.

     */

    public interface ProblemsCollector {

        /**

         * Collect current project problems.

         * @return list of current project problems, can be empty but never {@code null}

         */

        @NonNull

        Collection<? extends ProjectProblemsProvider.ProjectProblem> collectProblems();

    }

}