package org.activityinfo.ui.client.local.command;

/*
 * #%L
 * ActivityInfo Server
 * %%
 * Copyright (C) 2009 - 2013 UNICEF
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the 
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public 
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/gpl-3.0.html>.
 * #L%
 */

import com.extjs.gxt.ui.client.event.Listener;
import com.google.inject.ImplementedBy;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import org.activityinfo.ui.client.EventBus;
import org.activityinfo.ui.client.local.sync.ServerStateChangeEvent;
import org.activityinfo.ui.client.local.sync.SyncCompleteEvent;
import org.activityinfo.ui.client.local.sync.SyncRequestEvent;
import org.activityinfo.ui.client.local.sync.SyncStatusEvent;

@Singleton
public class OutOfSyncMonitor {

    private final EventBus eventBus;
    private boolean syncing = false;

    private int time = 0;
    private int timeLastSyncBegan = -1;
    private int timeLastServerMutation = -2;

    private boolean outOfSync = false;

    @ImplementedBy(OutOfSyncStatus.class)
    public interface View {
        void hide();

        void show();
    }

    private View view;

    @Inject
    public OutOfSyncMonitor(EventBus eventBus, View view) {
        super();
        this.eventBus = eventBus;
        this.view = view;

        this.eventBus.addListener(SyncCompleteEvent.TYPE, new Listener<SyncCompleteEvent>() {

            @Override
            public void handleEvent(SyncCompleteEvent be) {
                onSyncComplete();
            }
        });
        this.eventBus.addListener(SyncStatusEvent.TYPE, new Listener<SyncStatusEvent>() {

            @Override
            public void handleEvent(SyncStatusEvent be) {
                if (!syncing) {
                    onSyncStarted();
                }
            }
        });
        this.eventBus.addListener(ServerStateChangeEvent.TYPE, new Listener<ServerStateChangeEvent>() {

            @Override
            public void handleEvent(ServerStateChangeEvent be) {
                onServerStateMutated();
            }
        });
    }

    public void onServerStateMutated() {
        outOfSync = true;
        timeLastServerMutation = time++;

        if (!syncing) {
            eventBus.fireEvent(SyncRequestEvent.INSTANCE);
        }
        view.show();
    }

    private void onSyncStarted() {
        syncing = true;
        timeLastSyncBegan = time++;
    }

    private void onSyncComplete() {
        if (timeLastSyncBegan > timeLastServerMutation) {
            // sync started after mutation, so we
            // should have the latest results
            outOfSync = false;
            view.hide();
        } else {
            eventBus.fireEvent(SyncRequestEvent.INSTANCE);
        }
        syncing = false;
    }

    public boolean isOutOfSync() {
        return outOfSync;
    }
}