/* RequestCounter.java
 *
 * Copyright 2009-2012 Comcast Interactive Media, LLC.
 *
 * 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.fishwife.jrugged;

import java.util.concurrent.Callable;

/**
 * This is a statistics wrapper that counts total requests, as well as how many succeed
 * and how many fail. This class can be polled periodically to measure request rates,
 * success rates, and failure rates.
 */
public class RequestCounter implements ServiceWrapper {
    private long numRequests = 0L;
    private long numSuccesses = 0L;
    private long numFailures = 0L;

    /** Default constructor. */
    public RequestCounter() {
    }

    private synchronized void succeed() {
        numRequests++;
        numSuccesses++;
    }

    private synchronized void fail() {
        numRequests++;
        numFailures++;
    }

    /**
     * Wrap the given service call with the {@link RequestCounter} to count the number of
     * calls made.
     *
     * @param c
     *            the {@link Callable} to attempt
     *
     * @return whatever c would return on success
     *
     * @throws Exception
     *             if <code>c</code> throws one during execution
     */
    @Override
    public <T> T invoke(final Callable<T> c) throws Exception {
        try {
            final T result = c.call();
            succeed();
            return result;
        } catch (final Exception e) {
            fail();
            throw e;
        }
    }

    /**
     * Wrap the given service call with the {@link RequestCounter} to count the number of
     * calls made.
     *
     * @param r
     *            the {@link Runnable} to attempt
     *
     * @throws Exception
     *             if <code>c</code> throws one during execution
     */
    @Override
    public void invoke(final Runnable r) throws Exception {
        try {
            r.run();
            succeed();
        } catch (final Exception e) {
            fail();
            throw e;
        }
    }

    /**
     * Wrap the given service call with the {@link RequestCounter} to count the number of
     * calls made.
     *
     * @param r
     *            the {@link Runnable} to attempt
     * @param result
     *            what to return after <code>r</code> succeeds
     *
     * @return result
     *
     * @throws Exception
     *             if <code>c</code> throws one during execution
     */
    @Override
    public <T> T invoke(final Runnable r, final T result) throws Exception {
        try {
            r.run();
            succeed();
            return result;
        } catch (final Exception e) {
            fail();
            throw e;
        }
    }

    /**
     * Samples the current counts.
     *
     * @return an array of three <code>longs</code>: the total number of requests, the
     *         number of successful requests, and the number of failed requests.
     */
    public synchronized long[] sample() {
        return new long[] { numRequests, numSuccesses, numFailures };
    }

}