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.google.gwt.user.client.Timer;
import com.google.gwt.user.client.rpc.AsyncCallback;
import com.google.gwt.user.client.rpc.InvocationException;
import com.google.inject.Inject;
import org.activityinfo.legacy.client.Dispatcher;
import org.activityinfo.legacy.client.remote.AbstractDispatcher;
import org.activityinfo.legacy.client.remote.Remote;
import org.activityinfo.legacy.shared.command.Command;
import org.activityinfo.legacy.shared.command.result.CommandResult;
import org.activityinfo.ui.client.EventBus;

/**
 * Dispatcher implementation used by the synchronizer classes that executes
 * commands directly without caching, and retries aggressively.
 */
public class SynchronizerDispatcher extends AbstractDispatcher {

    private final EventBus eventBus;
    private final Dispatcher remoteDispatcher;

    private static final int MAX_RETRY_COUNT = 16;

    @Inject
    public SynchronizerDispatcher(EventBus eventBus, @Remote Dispatcher remoteDispatcher) {
        super();
        this.eventBus = eventBus;
        this.remoteDispatcher = remoteDispatcher;
    }

    @Override
    public <T extends CommandResult> void execute(Command<T> command, AsyncCallback<T> callback) {

        tryExecute(command, callback, 0);

    }

    private final <T extends CommandResult> void tryExecute(final Command<T> command,
                                                            final AsyncCallback<T> callback,
                                                            final int attempt) {
        remoteDispatcher.execute(command, null, new AsyncCallback<T>() {

            @Override
            public void onFailure(Throwable caught) {
                if (caught instanceof InvocationException) {
                    handleConnectionFailure(command, caught, callback, attempt);
                } else {
                    callback.onFailure(caught);
                }
            }

            @Override
            public void onSuccess(T result) {
                callback.onSuccess(result);
            }
        });
    }

    private final <T extends CommandResult> void handleConnectionFailure(final Command<T> command,
                                                                         Throwable caught,
                                                                         final AsyncCallback<T> callback,
                                                                         final int attempt) {
        if (attempt > MAX_RETRY_COUNT) {
            callback.onFailure(new SyncException(SyncErrorType.CONNECTION_PROBLEM, caught));
        } else {
            int delay = retryDelay(attempt);
            Timer timer = new Timer() {

                @Override
                public void run() {
                    tryExecute(command, callback, attempt + 1);
                }
            };
            timer.schedule(delay);
        }
    }

    private int retryDelay(final int attempt) {
        return (int) Math.pow(2, attempt);
    }
}