/*******************************************************************************
 * 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.graph.impl.contribution;

import org.simantics.browsing.ui.BuiltinKeys.LabelDecoratorKey;
import org.simantics.browsing.ui.DataSource;
import org.simantics.browsing.ui.NodeContext;
import org.simantics.browsing.ui.PrimitiveQueryUpdater;
import org.simantics.browsing.ui.content.LabelDecorator;
import org.simantics.browsing.ui.graph.impl.request.ResourceQuery;
import org.simantics.db.ReadGraph;
import org.simantics.db.exception.DatabaseException;
import org.simantics.db.procedure.Listener;
import org.simantics.db.procedure.Procedure;
import org.simantics.utils.ui.ErrorLogger;

public abstract class FinalLabelDecoratorContributionImpl extends LabelDecorator.Stub {

    final LabelDecorator FRESH = new LabelDecorator.Stub();
    final LabelDecorator PENDING = new LabelDecorator.Stub();
    final LabelDecorator NO_DECORATION = new LabelDecorator.Stub();

    protected final PrimitiveQueryUpdater       updater;
    private final ResourceQuery<LabelDecorator> labelQuery;
    private final LabelDecoratorKey             key;

    /**
     * The current decorator result produced for this contribution. The value
     * should never be <code>null</code>, but one of {@link #FRESH},
     * {@link #PENDING}, {@link #NO_DECORATION} instead.
     */
    protected LabelDecorator                      decorator = FRESH;

    final protected NodeContext                   context;

    public Object getIdentity(LabelDecoratorKey key) {
        return key;
    }

    private void request() {

        final DataSource<ReadGraph> source = updater.getDataSource(ReadGraph.class);
        assert(source != null);
        
        final Procedure<LabelDecorator> procedure = createProcedure();

        source.schedule(graph -> {
            if(procedure instanceof Listener<?>)
                graph.asyncRequest(labelQuery, (Listener<LabelDecorator>)procedure);
            else
                graph.asyncRequest(labelQuery, procedure);
        });

    }



    @Override
    public <Color_> Color_ decorateBackground(Color_ color, String column, int itemIndex) {
        if(FRESH == decorator) {
            decorator = PENDING;
            request();
        }
        return decorator.decorateBackground(color, column, itemIndex);
    }

    @Override
    public <Font_> Font_ decorateFont(Font_ font, String column, int itemIndex) {
        if(FRESH == decorator) {
            decorator = PENDING;
            request();
        }
        return decorator.decorateFont(font, column, itemIndex);
    }

    @Override
    public String decorateLabel(String label, String column, int itemIndex) {
        if(FRESH == decorator) {
            decorator = PENDING;
            request();
        }
        return decorator.decorateLabel(label, column, itemIndex);
    }

    @Override
    public <Color_> Color_ decorateForeground(Color_ color, String column, int itemIndex) {
        if(FRESH == decorator) {
            decorator = PENDING;
            request();
        }
        return decorator.decorateForeground(color, column, itemIndex);
    }

    public FinalLabelDecoratorContributionImpl(final PrimitiveQueryUpdater updater, final NodeContext context, final LabelDecoratorKey key) {

        this.updater = updater;
        this.context = context;
        this.key = key;

        labelQuery = new ResourceQuery<LabelDecorator>(getIdentity(key), context) {

            @Override
            public LabelDecorator perform(ReadGraph graph) throws DatabaseException {
                try {
                    return getDecorator(graph, context);
                } catch (DatabaseException e) {
                    throw e;
                } catch (Throwable t) {
                    ErrorLogger.defaultLogError("LazyGraphLabeler.labelQuery produced unexpected exception.", t);
                    return null;
                }
            }

            @Override
            public String toString() {
                return FinalLabelDecoratorContributionImpl.this + " with context " + context;
            }

        };

    }

    protected Procedure<LabelDecorator> createProcedure() {

        return new Procedure<LabelDecorator>() {

            @Override
            public void execute(LabelDecorator result) {
                replaceResult(result);
            }

            @Override
            public void exception(Throwable t) {
                ErrorLogger.defaultLogError("LazyContributionImpl.childQuery failed, see exception for details.", t);
            }

        };

    }

    protected void replaceResult(LabelDecorator result) {
        // Never let decorator become null, use a stub decorator instead.
        if (result == null)
            result = NO_DECORATION;

        decorator = result;
        updater.scheduleReplace(context, key, this);
    }

    // OVERRIDE

    public abstract LabelDecorator getDecorator(ReadGraph graph, NodeContext context) throws DatabaseException;

}