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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * The Universal Permissive License (UPL), Version 1.0
 *
 * Subject to the condition set forth below, permission is hereby granted to any
 * person obtaining a copy of this software, associated documentation and/or
 * data (collectively the "Software"), free of charge and under any and all
 * copyright rights in the Software, and any and all patent rights owned or
 * freely licensable by each licensor hereunder covering either (i) the
 * unmodified Software as contributed to or provided by such licensor, or (ii)
 * the Larger Works (as defined below), to deal in both
 *
 * (a) the Software, and
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 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
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 * Software and the Larger Work(s), and to sublicense the foregoing rights on
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package com.oracle.truffle.js.runtime.util;

import java.io.PrintStream;
import java.util.ArrayList;
import java.util.concurrent.atomic.AtomicLong;

import com.oracle.truffle.js.runtime.JSConfig;

public abstract class DebugCounter {
    private DebugCounter() {
    }

    public abstract long get();

    public abstract void inc();

    public static DebugCounter create(String name) {
        return JSConfig.DebugCounters ? DebugCounterImpl.createImpl(name) : Dummy.INSTANCE;
    }

    public static void dumpCounters() {
        if (JSConfig.DebugCounters) {
            DebugCounterImpl.dumpCounters(System.out);
        }
    }

    private static final class DebugCounterImpl extends DebugCounter {
        private static final ArrayList<DebugCounter> allCounters = new ArrayList<>();
        static {
            assert JSConfig.DebugCounters;
            Runtime.getRuntime().addShutdownHook(new Thread(() -> {
                dumpCounters(System.out);
            }));
        }

        private final String name;
        private final AtomicLong value;

        private DebugCounterImpl(String name) {
            this.name = name;
            this.value = new AtomicLong();
            allCounters.add(this);
        }

        private static DebugCounter createImpl(String name) {
            return new DebugCounterImpl(name);
        }

        @Override
        public long get() {
            return value.get();
        }

        @Override
        public void inc() {
            value.incrementAndGet();
        }

        @Override
        public String toString() {
            return name + ": " + get();
        }

        private static void dumpCounters(PrintStream out) {
            for (DebugCounter counter : allCounters) {
                out.println(counter);
            }
        }
    }

    private static final class Dummy extends DebugCounter {
        static final DebugCounter INSTANCE = new Dummy();

        private Dummy() {
        }

        @Override
        public long get() {
            return 0;
        }

        @Override
        public void inc() {
        }
    }
}