/*

 * Copyright (c) 2014, 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.

 */

import java.util.Objects;

import java.util.function.BiConsumer;

import java.util.function.Function;

import sun.hotspot.WhiteBox;

import sun.management.*;

import com.sun.management.*;

import com.oracle.java.testlibrary.*;

public final class VmFlagTest<T> {

    public static final WhiteBox WHITE_BOX = WhiteBox.getWhiteBox();

    private static final String NONEXISTENT_FLAG = "NonexistentFlag";

    private final String flagName;

    private final BiConsumer<T, T> test;

    private final BiConsumer<String, T> set;

    private final Function<String, T> get;

    protected VmFlagTest(String flagName, BiConsumer<String, T> set,

            Function<String, T> get, boolean isPositive) {

        this.flagName = flagName;

        this.set = set;

        this.get = get;

        if (isPositive) {

            test = this::testPositive;

        } else {

            test = this::testNegative;

        }

    }

    private void setNewValue(T value) {

        set.accept(flagName, value);

    }

    private T getValue() {

        return get.apply(flagName);

    }

    protected static <T> void runTest(String existentFlag, T[] tests,

            BiConsumer<String, T> set, Function<String, T> get) {

        runTest(existentFlag, tests, tests, set, get);

    }

    protected static <T> void runTest(String existentFlag, T[] tests,

            T[] results, BiConsumer<String, T> set, Function<String, T> get) {

        if (existentFlag != null) {

            new VmFlagTest(existentFlag, set, get, true).test(tests, results);

        }

        new VmFlagTest(NONEXISTENT_FLAG, set, get, false).test(tests, results);

    }

    public final void test(T[] tests, T[] results) {

        Asserts.assertEQ(tests.length, results.length, "[TESTBUG] tests.length != results.length");

        for (int i = 0, n = tests.length ; i < n; ++i) {

            test.accept(tests[i], results[i]);

        }

    }

    protected String getVMOptionAsString() {

        HotSpotDiagnosticMXBean diagnostic

                = ManagementFactoryHelper.getDiagnosticMXBean();

        VMOption tmp;

        try {

            tmp = diagnostic.getVMOption(flagName);

        } catch (IllegalArgumentException e) {

            tmp = null;

        }

        return tmp == null ? null : tmp.getValue();

    }

    private void testPositive(T value, T expected) {

        setNewValue(value);

        String newValue = getVMOptionAsString();

        Asserts.assertEQ(newValue, asString(expected));

    }

    private void testNegative(T value, T expected) {

        String oldValue = getVMOptionAsString();

        Asserts.assertEQ(oldValue, asString(getValue()));

        setNewValue(value);

        String newValue = getVMOptionAsString();

        Asserts.assertEQ(oldValue, newValue);

    }

    private String asString(Object value) {

        return value == null ? null : "" + value;

    }

}