/*

 * Copyright (c) 2010, 2013, 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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.

 */

/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file, and Oracle licenses the original version of this file under the BSD

 * license:

 */

/*

   Copyright 2009-2013 Attila Szegedi

*/

package jdk.dynalink.linker.support;

import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodHandles;

import java.lang.invoke.MethodType;

import java.util.logging.Level;

import java.util.logging.Logger;

import jdk.dynalink.DynamicLinker;

import jdk.dynalink.linker.LinkerServices;

/**

 * Utility methods for creating typical guards for

 * {@link MethodHandles#guardWithTest(MethodHandle, MethodHandle, MethodHandle)}

 * and for adjusting their method types.

 */

public final class Guards {

    private static final Logger LOG = Logger

            .getLogger(Guards.class.getName(), "jdk.dynalink.support.messages");

    private Guards() {

    }

    /**

     * Creates a guard method handle with arguments of a specified type, but with boolean return value. When invoked, it

     * returns true if the first argument is of the specified class (exactly of it, not a subclass). The rest of the

     * arguments will be ignored.

     *

     * @param clazz the class of the first argument to test for

     * @param type the method type

     * @return a method handle testing whether its first argument is of the specified class.

     */

    @SuppressWarnings("boxing")

    public static MethodHandle isOfClass(final Class<?> clazz, final MethodType type) {

        final Class<?> declaredType = type.parameterType(0);

        if(clazz == declaredType) {

            LOG.log(Level.WARNING, "isOfClassGuardAlwaysTrue", new Object[] { clazz.getName(), 0, type, DynamicLinker.getLinkedCallSiteLocation() });

            return constantTrue(type);

        }

        if(!declaredType.isAssignableFrom(clazz)) {

            LOG.log(Level.WARNING, "isOfClassGuardAlwaysFalse", new Object[] { clazz.getName(), 0, type, DynamicLinker.getLinkedCallSiteLocation() });

            return constantFalse(type);

        }

        return getClassBoundArgumentTest(IS_OF_CLASS, clazz, 0, type);

    }

    /**

     * Creates a method handle with arguments of a specified type, but with boolean return value. When invoked, it

     * returns true if the first argument is instance of the specified class or its subclass). The rest of the arguments

     * will be ignored.

     *

     * @param clazz the class of the first argument to test for

     * @param type the method type

     * @return a method handle testing whether its first argument is of the specified class or subclass.

     */

    public static MethodHandle isInstance(final Class<?> clazz, final MethodType type) {

        return isInstance(clazz, 0, type);

    }

    /**

     * Creates a method handle with arguments of a specified type, but with boolean return value. When invoked, it

     * returns true if the n'th argument is instance of the specified class or its subclass). The rest of the arguments

     * will be ignored.

     *

     * @param clazz the class of the first argument to test for

     * @param pos the position on the argument list to test

     * @param type the method type

     * @return a method handle testing whether its first argument is of the specified class or subclass.

     */

    @SuppressWarnings("boxing")

    public static MethodHandle isInstance(final Class<?> clazz, final int pos, final MethodType type) {

        final Class<?> declaredType = type.parameterType(pos);

        if(clazz.isAssignableFrom(declaredType)) {

            LOG.log(Level.WARNING, "isInstanceGuardAlwaysTrue", new Object[] { clazz.getName(), pos, type, DynamicLinker.getLinkedCallSiteLocation() });

            return constantTrue(type);

        }

        if(!declaredType.isAssignableFrom(clazz)) {

            LOG.log(Level.WARNING, "isInstanceGuardAlwaysFalse", new Object[] { clazz.getName(), pos, type, DynamicLinker.getLinkedCallSiteLocation() });

            return constantFalse(type);

        }

        return getClassBoundArgumentTest(IS_INSTANCE, clazz, pos, type);

    }

    /**

     * Creates a method handle that returns true if the argument in the specified position is a Java array.

     *

     * @param pos the position in the argument lit

     * @param type the method type of the handle

     * @return a method handle that returns true if the argument in the specified position is a Java array; the rest of

     * the arguments are ignored.

     */

    @SuppressWarnings("boxing")

    public static MethodHandle isArray(final int pos, final MethodType type) {

        final Class<?> declaredType = type.parameterType(pos);

        if(declaredType.isArray()) {

            LOG.log(Level.WARNING, "isArrayGuardAlwaysTrue", new Object[] { pos, type, DynamicLinker.getLinkedCallSiteLocation() });

            return constantTrue(type);

        }

        if(!declaredType.isAssignableFrom(Object[].class)) {

            LOG.log(Level.WARNING, "isArrayGuardAlwaysFalse", new Object[] { pos, type, DynamicLinker.getLinkedCallSiteLocation() });

            return constantFalse(type);

        }

        return asType(IS_ARRAY, pos, type);

    }

    private static MethodHandle getClassBoundArgumentTest(final MethodHandle test, final Class<?> clazz, final int pos, final MethodType type) {

        // Bind the class to the first argument of the test

        return asType(test.bindTo(clazz), pos, type);

    }

    /**

     * Takes a method handle intended to be used as a guard, and adapts it to

     * the requested type, but returning a boolean. Applies

     * {@link MethodHandle#asType(MethodType)} to convert types and uses

     * {@link MethodHandles#dropArguments(MethodHandle, int, Class...)} to match

     * the requested type arity.

     * @param test the test method handle

     * @param type the type to adapt the method handle to

     * @return the adapted method handle

     */

    public static MethodHandle asType(final MethodHandle test, final MethodType type) {

        return test.asType(getTestType(test, type));

    }

    /**

     * Takes a method handle intended to be used as a guard, and adapts it to

     * the requested type, but returning a boolean. Applies

     * {@link LinkerServices#asType(MethodHandle, MethodType)} to convert types

     * and uses

     * {@link MethodHandles#dropArguments(MethodHandle, int, Class...)} to match

     * the requested type arity.

     * @param linkerServices the linker services to use for type conversions

     * @param test the test method handle

     * @param type the type to adapt the method handle to

     * @return the adapted method handle

     */

    public static MethodHandle asType(final LinkerServices linkerServices, final MethodHandle test, final MethodType type) {

        return linkerServices.asType(test, getTestType(test, type));

    }

    private static MethodType getTestType(final MethodHandle test, final MethodType type) {

        return type.dropParameterTypes(test.type().parameterCount(),

                type.parameterCount()).changeReturnType(boolean.class);

    }

    private static MethodHandle asType(final MethodHandle test, final int pos, final MethodType type) {

        assert test != null;

        assert type != null;

        assert type.parameterCount() > 0;

        assert pos >= 0 && pos < type.parameterCount();

        assert test.type().parameterCount() == 1;

        assert test.type().returnType() == Boolean.TYPE;

        return MethodHandles.permuteArguments(test.asType(test.type().changeParameterType(0, type.parameterType(pos))),

                type.changeReturnType(Boolean.TYPE), new int[] { pos });

    }

    private static final MethodHandle IS_INSTANCE = Lookup.PUBLIC.findVirtual(Class.class, "isInstance",

            MethodType.methodType(Boolean.TYPE, Object.class));

    private static final MethodHandle IS_OF_CLASS;

    private static final MethodHandle IS_ARRAY;

    private static final MethodHandle IS_IDENTICAL;

    private static final MethodHandle IS_NULL;

    private static final MethodHandle IS_NOT_NULL;

    static {

        final Lookup lookup = new Lookup(MethodHandles.lookup());

        IS_OF_CLASS  = lookup.findOwnStatic("isOfClass",   Boolean.TYPE, Class.class, Object.class);

        IS_ARRAY     = lookup.findOwnStatic("isArray",     Boolean.TYPE, Object.class);

        IS_IDENTICAL = lookup.findOwnStatic("isIdentical", Boolean.TYPE, Object.class, Object.class);

        IS_NULL      = lookup.findOwnStatic("isNull",      Boolean.TYPE, Object.class);

        IS_NOT_NULL  = lookup.findOwnStatic("isNotNull",   Boolean.TYPE, Object.class);

    }

    /**

     * Creates a guard method that tests its only argument for being of an exact particular class.

     * @param clazz the class to test for.

     * @return the desired guard method.

     */

    public static MethodHandle getClassGuard(final Class<?> clazz) {

        return IS_OF_CLASS.bindTo(clazz);

    }

    /**

     * Creates a guard method that tests its only argument for being an instance of a particular class.

     * @param clazz the class to test for.

     * @return the desired guard method.

     */

    public static MethodHandle getInstanceOfGuard(final Class<?> clazz) {

        return IS_INSTANCE.bindTo(clazz);

    }

    /**

     * Creates a guard method that tests its only argument for being referentially identical to another object

     * @param obj the object used as referential identity test

     * @return the desired guard method.

     */

    public static MethodHandle getIdentityGuard(final Object obj) {

        return IS_IDENTICAL.bindTo(obj);

    }

    /**

     * Returns a guard that tests whether the first argument is null.

     * @return a guard that tests whether the first argument is null.

     */

    public static MethodHandle isNull() {

        return IS_NULL;

    }

    /**

     * Returns a guard that tests whether the first argument is not null.

     * @return a guard that tests whether the first argument is not null.

     */

    public static MethodHandle isNotNull() {

        return IS_NOT_NULL;

    }

    @SuppressWarnings("unused")

    private static boolean isNull(final Object obj) {

        return obj == null;

    }

    @SuppressWarnings("unused")

    private static boolean isNotNull(final Object obj) {

        return obj != null;

    }

    @SuppressWarnings("unused")

    private static boolean isArray(final Object o) {

        return o != null && o.getClass().isArray();

    }

    @SuppressWarnings("unused")

    private static boolean isOfClass(final Class<?> c, final Object o) {

        return o != null && o.getClass() == c;

    }

    @SuppressWarnings("unused")

    private static boolean isIdentical(final Object o1, final Object o2) {

        return o1 == o2;

    }

    private static MethodHandle constantTrue(final MethodType type) {

        return constantBoolean(Boolean.TRUE, type);

    }

    private static MethodHandle constantFalse(final MethodType type) {

        return constantBoolean(Boolean.FALSE, type);

    }

    private static MethodHandle constantBoolean(final Boolean value, final MethodType type) {

        return MethodHandles.permuteArguments(MethodHandles.constant(Boolean.TYPE, value),

                type.changeReturnType(Boolean.TYPE));

    }

}