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

/*
 * #%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.bedatadriven.rebar.async.Async;
import com.bedatadriven.rebar.async.AsyncCommand;
import com.bedatadriven.rebar.async.AsyncFunction;
import com.google.gwt.user.client.rpc.AsyncCallback;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import org.activityinfo.legacy.client.Dispatcher;
import org.activityinfo.legacy.shared.command.result.CommandResult;
import org.activityinfo.ui.client.local.command.CommandQueue;
import org.activityinfo.ui.client.local.command.CommandQueue.QueueEntry;

/**
 * Sends updates to the remote database.
 */
@Singleton
public class UpdateSynchronizer implements AsyncCommand {

    private CommandQueue commandQueue;
    private Dispatcher dispatcher;

    @Inject
    public UpdateSynchronizer(CommandQueue commandQueue, SynchronizerDispatcher dispatcher) {
        super();
        this.commandQueue = commandQueue;
        this.dispatcher = dispatcher;
    }

    private AsyncFunction<QueueEntry, CommandResult> dispatch() {
        return new AsyncFunction<CommandQueue.QueueEntry, CommandResult>() {

            @Override
            protected void doApply(QueueEntry argument, AsyncCallback<CommandResult> callback) {
                dispatcher.execute(argument.getCommand(), callback);
            }
        };
    }

    @Override
    public void execute(AsyncCallback<Void> callback) {
        commandQueue.get().map(Async.sequence(dispatch(), commandQueue.remove())).discardResult().apply(null, callback);
    }

}