/*
 * Copyright (c) 2014, 2019, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package jdk.vm.ci.common;

import java.util.concurrent.atomic.AtomicInteger;

import jdk.vm.ci.services.Services;

/**
 * A facility for timing a step in the runtime initialization sequence. This is independent from all
 * other JVMCI code so as to not perturb the initialization sequence. It is enabled by setting the
 * {@code "jvmci.inittimer"} system property to {@code "true"}.
 */
public final class InitTimer implements AutoCloseable {
    private final String name;
    private final long start;

    private InitTimer(String name) {
        int n = nesting.getAndIncrement();
        if (n == 0) {
            initializingThread = Thread.currentThread();
            System.out.println("INITIALIZING THREAD: " + initializingThread);
        } else {
            assert Thread.currentThread() == initializingThread : Thread.currentThread() + " != " + initializingThread;
        }
        this.name = name;
        this.start = System.currentTimeMillis();
        System.out.println("START: " + SPACES.substring(0, n * 2) + name);
    }

    @Override
    @SuppressFBWarnings(value = "ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD", justification = "only the initializing thread accesses this field")
    public void close() {
        final long end = System.currentTimeMillis();
        int n = nesting.decrementAndGet();
        System.out.println(" DONE: " + SPACES.substring(0, n * 2) + name + " [" + (end - start) + " ms]");
        if (n == 0) {
            initializingThread = null;
        }
    }

    public static InitTimer timer(String name) {
        return isEnabled() ? new InitTimer(name) : null;
    }

    public static InitTimer timer(String name, Object suffix) {
        return isEnabled() ? new InitTimer(name + suffix) : null;
    }

    /**
     * Determines if initialization timing is enabled. Note: This property cannot use
     * {@code HotSpotJVMCIRuntime.Option} since that class is not visible from this package.
     */
    private static boolean isEnabled() {
        if (enabledPropertyValue == null) {
            enabledPropertyValue = Boolean.parseBoolean(Services.getSavedProperty("jvmci.InitTimer"));
            nesting = new AtomicInteger();
        }
        return enabledPropertyValue;
    }

    /**
     * Cache for value of {@code jvmci.InitTimer} system property.
     */
    @NativeImageReinitialize private static Boolean enabledPropertyValue;

    private static AtomicInteger nesting;
    private static final String SPACES = "                                            ";

    /**
     * Used to assert the invariant that all related initialization happens on the same thread.
     */
    static Thread initializingThread;
}