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Utility classes developed at Adrian Smith Software (A.S.S.)
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package com.databasesandlife.util;

import java.util.HashMap;
import java.util.Locale;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Times a calculation.
 *    
 * Usage:
 * 
try (Timer ignored = new Timer("doing something")) { ... }
 *
 * @author This source is copyright Adrian Smith and licensed under the LGPL 3.
 * @see Project on GitHub
 */
public class Timer implements AutoCloseable {

    static Logger logger = LoggerFactory.getLogger(Timer.class);
    static ThreadLocal> start = new ThreadLocal<>();

    protected static String getPrefix() {
        var count = start.get().size();

        if (count >= 10) {
            return "I x"+count+" ";
        } else {
            return "I ".repeat(count);
        }
    }

    /** @deprecated use try (Timer ignored = new Timer("...")) { .. } instead */
    @Deprecated public static void start(String name) {
        if (start.get() == null) start.set(new HashMap());

        if (start.get().containsKey(name)) {
            logger.warn("Timer start '"+name+"' but this name is already active");
            return;
        }

        logger.info(getPrefix() + "'" + name + "' start");
        start.get().put(name, System.nanoTime());
    }
    
    public static String formatDurationNanos(long durationNanoSeconds) {
        var seconds = durationNanoSeconds / (1000*1000*1000.0);
        
        var minutes = (int) seconds / 60;
        seconds -= 60 * minutes;

        var hours = (int) minutes / 60;       
        minutes -= 60 * hours;
        
        var hoursStr = (hours == 0) ? "" : (hours + " hrs ");
        var minutesStr = (hours == 0 && minutes == 0) ? "" : (minutes + " min ");

        return String.format(Locale.ENGLISH, "%s%s%.3f sec", hoursStr, minutesStr, seconds);
    }

    /** @deprecated use try (Timer ignored = new Timer("...")) { .. } instead */
    @Deprecated public static void end(String name) {
        if (start.get() == null) start.set(new HashMap());

        if ( ! start.get().containsKey(name)) {
            logger.warn("Timer end '" + name + "' but was never started");
            return;
        }

        var durationNanos = System.nanoTime() - start.get().get(name);
        start.get().remove(name);

        logger.info(String.format("%s'%s' end (%s)", getPrefix(), name, formatDurationNanos(durationNanos)));
    }

    protected String name;
    public Timer(String x) { Timer.start(name = x); }
    @Override public void close()  { Timer.end(name); }
}