/*

 * 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.beans;

import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodType;

import java.security.AccessControlContext;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.Arrays;

import java.util.LinkedList;

import java.util.List;

import jdk.dynalink.internal.AccessControlContextFactory;

import jdk.dynalink.internal.InternalTypeUtilities;

import jdk.dynalink.linker.LinkerServices;

import jdk.dynalink.linker.support.TypeUtilities;

/**

 * Represents a sequence of {@link Class} objects, useful for representing method signatures. Provides value

 * semantics for using them as map keys, as well as specificity calculations and applicability checks as per

 * JLS.

 */

final class ClassString {

    private static final AccessControlContext GET_CLASS_LOADER_CONTEXT =

            AccessControlContextFactory.createAccessControlContext("getClassLoader");

    /**

     * An anonymous inner class used solely to represent the "type" of null values for method applicability checking.

     */

    static final Class<?> NULL_CLASS = (new Object() { /* Intentionally empty */ }).getClass();

    private final Class<?>[] classes;

    private int hashCode;

    ClassString(final Class<?>[] classes) {

        this.classes = classes;

    }

    ClassString(final MethodType type) {

        this(type.parameterArray());

    }

    @Override

    public boolean equals(final Object other) {

        if(!(other instanceof ClassString)) {

            return false;

        }

        final Class<?>[] otherClasses = ((ClassString)other).classes;

        if(otherClasses.length != classes.length) {

            return false;

        }

        for(int i = 0; i < otherClasses.length; ++i) {

            if(otherClasses[i] != classes[i]) {

                return false;

            }

        }

        return true;

    }

    @Override

    public int hashCode() {

        if(hashCode == 0) {

            int h = 0;

            for(int i = 0; i < classes.length; ++i) {

                h ^= classes[i].hashCode();

            }

            hashCode = h;

        }

        return hashCode;

    }

    @Override

    public String toString() {

        return "ClassString[" + Arrays.toString(classes) + "]";

    }

    boolean isVisibleFrom(final ClassLoader classLoader) {

        return AccessController.doPrivileged(new PrivilegedAction<Boolean>() {

            @Override

            public Boolean run() {

                for(final Class<?> clazz: classes) {

                    if(!InternalTypeUtilities.canReferenceDirectly(classLoader, clazz.getClassLoader())) {

                        return false;

                    }

                }

                return true;

            }

        }, GET_CLASS_LOADER_CONTEXT);

    }

    List<MethodHandle> getMaximallySpecifics(final List<MethodHandle> methods, final LinkerServices linkerServices, final boolean varArg) {

        return MaximallySpecific.getMaximallySpecificMethodHandles(getApplicables(methods, linkerServices, varArg),

                varArg, classes, linkerServices);

    }

    /**

     * Returns all methods that are applicable to actual parameter classes represented by this ClassString object.

     */

    LinkedList<MethodHandle> getApplicables(final List<MethodHandle> methods, final LinkerServices linkerServices, final boolean varArg) {

        final LinkedList<MethodHandle> list = new LinkedList<>();

        for(final MethodHandle member: methods) {

            if(isApplicable(member, linkerServices, varArg)) {

                list.add(member);

            }

        }

        return list;

    }

    /**

     * Returns true if the supplied method is applicable to actual parameter classes represented by this ClassString

     * object.

     *

     */

    private boolean isApplicable(final MethodHandle method, final LinkerServices linkerServices, final boolean varArg) {

        final Class<?>[] formalTypes = method.type().parameterArray();

        final int cl = classes.length;

        final int fl = formalTypes.length - (varArg ? 1 : 0);

        if(varArg) {

            if(cl < fl) {

                return false;

            }

        } else {

            if(cl != fl) {

                return false;

            }

        }

        // Starting from 1 as we ignore the receiver type

        for(int i = 1; i < fl; ++i) {

            if(!canConvert(linkerServices, classes[i], formalTypes[i])) {

                return false;

            }

        }

        if(varArg) {

            final Class<?> varArgType = formalTypes[fl].getComponentType();

            for(int i = fl; i < cl; ++i) {

                if(!canConvert(linkerServices, classes[i], varArgType)) {

                    return false;

                }

            }

        }

        return true;

    }

    private static boolean canConvert(final LinkerServices ls, final Class<?> from, final Class<?> to) {

        if(from == NULL_CLASS) {

            return !to.isPrimitive();

        }

        return ls == null ? TypeUtilities.isMethodInvocationConvertible(from, to) : ls.canConvert(from, to);

    }

}