/*
 * Copyright 2006 the original author or authors.
 *
 * 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 org.wamblee.test;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


/**
 * Tracks the occurence of certain events in a test environment. Threads in a
 * test environment tell the event tracker of the occurrence of certain events
 * using {@link #eventOccurred(Event)}. Test code inspects the events sent by a
 * thread using {@link #isEventSent(Thread, Event)}.
 *
 * A record is kept of every event which is sent. Therefore, the occurrence of a
 * new event does not erase a previously sent event.
 *
 * @param <Event>
 *            Type of event sent from test code. Usually String will be
 *            sufficient. The event type must provide a sensible implementation
 *            of {@link java.lang.Object#equals(java.lang.Object)}.
 *
 * @author Erik Brakkee
 */
public class EventTracker<Event> {
    private static final Log LOG = LogFactory.getLog(EventTracker.class);

    /**
     * Map of Thread object to a list of events.
     */
    private Map<Thread, List<Event>> events;

    /**
     * Constructs the event tracker.
     *
     */
    public EventTracker() {
        clear();
    }

    public void clear() {
        events = new HashMap<Thread, List<Event>>();
    }

    /**
     * Called by a thread to inform that an event has occurred.
     *
     * @param aEvent
     *            Event that was sent.
     */
    public synchronized void eventOccurred(Event aEvent) {
        LOG.info("Event '" + aEvent + "' sent.");

        Thread current = Thread.currentThread();
        List<Event> eventList = events.get(current);

        if (eventList == null) {
            eventList = new ArrayList<Event>();
            events.put(current, eventList);
        }

        eventList.add(aEvent);
    }

    /**
     * Checks if a specific event has happened in a specific thread.
     *
     * @param aThread
     *            Thread to check.
     * @param aEvent
     *            Event to check for.
     * @return Whether or not the event was sent.
     */
    public synchronized boolean isEventSent(Thread aThread, Event aEvent) {
        List<Event> eventList = events.get(aThread);

        if (eventList == null) {
            return false;
        }

        return eventList.contains(aEvent);
    }

    /**
     * Gets the events for a thread in the order they were sent
     *
     * @param aThread
     *            Thread to get events for.
     * @return Events that were sent. A zero-sized array is returned if no
     *         events were sent.
     */
    public synchronized List<Event> getEvents(Thread aThread) {
        List<Event> eventList = events.get(aThread);

        if (eventList == null) {
            eventList = Collections.emptyList();
        }

        return Collections.unmodifiableList(eventList);
    }

    /**
     * Gets the number of times an event was sent summed up
     * over all threads.
     *
     * @param aEvent
     *            Event to check.
     * @return Number of times it was reached.
     */
    public synchronized int getEventCount(Event aEvent) {
        int count = 0;

        for (Thread thread : events.keySet()) {
            List<Event> eventList = events.get(thread);

            for (Event event : eventList) {
                if (event.equals(aEvent)) {
                    count++;
                }
            }
        }

        return count;
    }

    /**
     * Gets the total event count over all threads.
     * @return
     */
    public synchronized int getEventCount() {
        int count = 0;

        for (Thread thread : events.keySet()) {
            count += events.get(thread).size();
        }

        return count;
    }
}