/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.jena.atlas.lib ;

import org.apache.jena.atlas.AtlasException ;

/** A Timer of operations */ 
public class Timer {

    protected long    timeFinish = -1 ;
    protected boolean inTimer    = false ;
    protected long    timeStart  = 0 ;

    public Timer() {}

    public void startTimer() {
        if ( inTimer )
            throw new AtlasException("Already in timer") ;
        timeStart = System.currentTimeMillis() ;
        timeFinish = -1 ;
        inTimer = true ;
    }

    /** Stop timing and return the elapsed time in milliseconds */
    public long endTimer() {
        if ( !inTimer )
            throw new AtlasException("Not in timer") ;
        timeFinish = System.currentTimeMillis() ;
        inTimer = false ;
        return getTimeInterval() ;
    }

    /** Read the timer - either the instantanious value (if running) or elapsed time (if finished). */  
    public long read() {
        return inTimer
            ? System.currentTimeMillis() - timeStart
            : timeFinish - timeStart;
    }
    
    /** Read a running timer */
    public long readTimer() {
        if ( !inTimer )
            throw new AtlasException("Not in timer") ;
        return read() ;
    }

    /** Read an elapsed timer */
    public long getTimeInterval() {
        if ( inTimer )
            throw new AtlasException("Still timing") ;
        if ( timeFinish == -1 )
            throw new AtlasException("No valid interval") ;
        return read() ;
    }

    /** Helper function to format milliseconds as "%.3f" seconds */
    static public String timeStr(long timeInterval) {
        return String.format("%.3f", timeInterval / 1000.0) ;
    }

    protected String timeStr(long timePoint, long startTimePoint) {
        return timeStr(timePoint - startTimePoint) ;
    }

    /** Time an operation. Return the elapsed time in milliseconds. */
    public static long time(Runnable action) {
        Timer timer = new Timer();
        timer.startTimer();
        action.run();
        long x = timer.endTimer();
        return x;
    }
}
