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package net.java.ao.benchmark.util;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.SortedMap;
import java.util.TreeMap;


public final class StopWatch {
    private final SortedMap laps = new TreeMap();

    private final String name;
    private long start;
    private long stop;
    private long lap;

    public StopWatch(String name) {
        this.name = Objects.requireNonNull(name, "name can't be null");
    }

    public String getName() {
        return name;
    }

    public void start() {
        start = now();
        lap = start;
        laps.clear();
    }

    public void lap(K k) {
        final long now = now();
        laps.put(k, now - lap);
        lap = now;
    }

    public void stop() {
        stop = now();
    }

    private long now() {
        return System.nanoTime();
    }

    private boolean isStopped() {
        return stop > 0;
    }

    public Report getReport() {
        if (!isStopped()) {
            throw new IllegalStateException("Stop watch must be stopped to generate report");
        }
        return new Report(name, start, stop, laps());
    }

    private List laps() {
        final List lapValues = new ArrayList(laps.size());
        for (Map.Entry e : laps.entrySet()) {
            lapValues.add(e.getValue());
        }
        return lapValues;
    }
}