//   Copyright 2012 Georg-August-Universität Göttingen, Germany
//
//   Licensed under the Apache License, Version 2.0 (the "License");
//   you may not use this file except in compliance with the License.
//   You may obtain a copy of the License at
//
//       http://www.apache.org/licenses/LICENSE-2.0
//
//   Unless required by applicable law or agreed to in writing, software
//   distributed under the License is distributed on an "AS IS" BASIS,
//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//   See the License for the specific language governing permissions and
//   limitations under the License.

package de.ugoe.cs.autoquest.tasktrees.manager;

import java.util.Collection;
import java.util.LinkedList;
import java.util.List;
import java.util.logging.Level;

import de.ugoe.cs.autoquest.eventcore.Event;
import de.ugoe.cs.autoquest.tasktrees.treeifc.IEventTask;
import de.ugoe.cs.autoquest.tasktrees.treeifc.ITaskModel;
import de.ugoe.cs.autoquest.tasktrees.treeifc.ITaskBuilder;
import de.ugoe.cs.autoquest.tasktrees.treeifc.ITaskFactory;
import de.ugoe.cs.autoquest.tasktrees.treeifc.IUserSession;
import de.ugoe.cs.util.console.Console;

/**
 * <p>
 * The task tree manager is responsible for transforming one or more user sessions into a task
 * model. It can be called by providing a collection of user sessions where the result
 * will be a task model. Furthermore, it can be used by providing single events in their respective
 * order including notifications about where a user session ends. The result is a task model,
 * as well. 
 * </p>
 * 
 * @version 1.0
 * @author pharms
 */
public class TaskTreeManager {
    
    /**
     * <p>
     * the internally used task builder
     * </p>
     */
    private ITaskBuilder taskBuilder = ComponentManager.getDefaultTaskBuilder();

    /**
     * <p>
     * the internally used task factory
     * </p>
     */
    private ITaskFactory taskFactory = ComponentManager.getDefaultTaskFactory();

    /**
     * <p>
     * if single events are provided, the user sessions collected so far
     * </p>
     */
    private List<IUserSession> sessions = null;

    /**
     * <p>
     * if single events are provided, the currently collected user session
     * </p>
     */
    private IUserSession currentSession = null;

    /**
     * <p>
     * initializes the task tree manager
     * </p>
     */
    public TaskTreeManager() {
        sessions = new LinkedList<IUserSession>();
    }

    /**
     * <p>
     * creates a task model based on the provided user sessions. Yet, the user sessions are
     * list of events. Such will be transformed in into task instances of event tasks assigned
     * to {@link IUserSession}s. The {@link IUserSession}s will then be restructured using
     * the temporal relationship rule manager to detect tasks and respective instances. The
     * results of this transformation is stored in a task model which is the return value of
     * this method.
     * </p>
     * 
     * @param newSessions the user sessions of which the task model shall be created
     * 
     * @return the task model created from the user sessions
     * 
     * @throws IllegalStateException if the task manager is already used by providing it with
     *                               single events
     */
    public synchronized ITaskModel createTaskModel(Collection<List<Event>> newSessions) {
        if ((currentSession != null) || (sessions.size() > 0)) {
            throw new IllegalStateException("do not mix calls to this method with calls to the " +
                                            "other methods for handling tasks. Use only one " +
                                            "variant instead.");
        }
        
        for (List<Event> newSession : newSessions) {
            if (newSession.size() > 0) {
                for (Event event : newSession) {
                    handleNewEvent(event);
                }
                finishSession();
            }
        }
        
        return getTaskModel();
    }

    /**
     * <p>
     * handles a single event that occurred in a user session.
     * </p>
     * 
     * @param event the event to handle
     */
    public void handleNewEvent(Event event) {
        assertSessionSequence();
        String description = event.getType().getName() + " \u21D2 " + event.getTarget();
        IEventTask eventTask = taskFactory.createNewEventTask(description);
        taskBuilder.addExecutedTask
            (currentSession, taskFactory.createNewTaskInstance(eventTask, event));
    }

    /**
     * <p>
     * used to denote, that all previously added events using {@link #handleNewEvent(Event)}
     * belong to the same session and that this session is now complete. All further events
     * will be added to a new session which may be ended using this method, as well.
     * </p>
     */
    public void finishSession() {
        if ((currentSession != null) && (currentSession.getExecutedTasks().size() > 0)) {
            sessions.add(currentSession);
            currentSession = null;
        }
    }

    /**
     * <p>
     * returns the task model, that belongs to the events in the user sessions collected so far.
     * </p>
     * 
     * @return the task model
     */
    public synchronized ITaskModel getTaskModel() {
        finishSession();
        
        Console.traceln(Level.INFO, "applying temporal relationship generation rules");
        
        ComponentManager.getTemporalRelationshipRuleManager().applyRules(sessions);

        return taskFactory.createTaskModel(sessions);
    }

    /**
     * <p>
     * internally asserts that there is a current session to add new events to
     * </p>
     */
    private void assertSessionSequence() {
        if (currentSession == null) {
            currentSession = taskFactory.createUserSession();
        }
    }

}
