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/*
 * Copyright 2014 WSO2 Inc. (http://wso2.org)
 * 
 * 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.wso2.carbon.metrics.manager;

import java.io.Closeable;
import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;

/**
 * A metric for measuring the duration of a particular piece of code
 */
public interface Timer extends Metric {

    /**
     * Adds a recorded duration.
     *
     * @param duration the length of the duration
     * @param unit the scale unit of {@code duration}
     */
    void update(long duration, TimeUnit unit);

    /**
     * Times and records the duration of event.
     *
     * @param event a {@link Callable} whose {@link Callable#call()} method implements a process whose duration should
     *            be timed
     * @param  the type of the value returned by {@code event}
     * @return the value returned by {@code event}
     * @throws Exception if {@code event} throws an {@link Exception}
     */
     T time(Callable event) throws Exception;

    /**
     * Returns a new {@link Context}
     *
     * @return a new {@link Context}
     * @see Context
     */
    Context start();

    long getCount();

    interface Context extends Closeable {

        /**
         * Updates the timer with the difference between current and start time. Call to this method will not reset the
         * start time. Multiple calls result in multiple updates.
         * 
         * @return the elapsed time in nanoseconds
         */
        long stop();

        void close();
    }

}