/*

 * Copyright (c) 2010, 2016, 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

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 */

/*

 * 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.reflect.Method;

import java.lang.reflect.Modifier;

import java.util.Arrays;

import java.util.Collection;

import java.util.HashMap;

import java.util.LinkedHashSet;

import java.util.Map;

import java.util.Set;

/**

 * Utility class for discovering accessible methods and inner classes. Normally, a public member declared on a class is

 * accessible (that is, it can be invoked from anywhere). However, this is not the case if the class itself is not

 * public, or belongs to a restricted-access package. In that case, it is required to lookup a member in a publicly

 * accessible superclass or implemented interface of the class, and use it instead of the member discovered on the

 * class.

 */

class AccessibleMembersLookup {

    private final Map<MethodSignature, Method> methods;

    private final Set<Class<?>> innerClasses;

    private final boolean instance;

    /**

     * Creates a mapping for all accessible methods and inner classes on a class.

     *

     * @param clazz the inspected class

     * @param instance true to inspect instance methods, false to inspect static methods.

     */

    AccessibleMembersLookup(final Class<?> clazz, final boolean instance) {

        this.methods = new HashMap<>();

        this.innerClasses = new LinkedHashSet<>();

        this.instance = instance;

        lookupAccessibleMembers(clazz);

    }

    /**

     * Returns an accessible method equivalent of a method.

     *

     * @param m the method whose accessible equivalent is requested.

     * @return the accessible equivalent for the method (can be the same as the passed in method), or null if there is

     * no accessible method equivalent.

     */

    Method getAccessibleMethod(final Method m) {

        return m == null ? null : methods.get(new MethodSignature(m));

    }

    Collection<Method> getMethods() {

        return methods.values();

    }

    Class<?>[] getInnerClasses() {

        return innerClasses.toArray(new Class<?>[0]);

    }

    /**

     * A helper class that represents a method signature - name and argument types.

     */

    static final class MethodSignature {

        private final String name;

        private final Class<?>[] args;

        /**

         * Creates a new method signature from arbitrary data.

         *

         * @param name the name of the method this signature represents.

         * @param args the argument types of the method.

         */

        MethodSignature(final String name, final Class<?>[] args) {

            this.name = name;

            this.args = args;

        }

        /**

         * Creates a signature for the given method.

         *

         * @param method the method for which a signature is created.

         */

        MethodSignature(final Method method) {

            this(method.getName(), method.getParameterTypes());

        }

        /**

         * Compares this object to another object

         *

         * @param o the other object

         * @return true if the other object is also a method signature with the same name, same number of arguments, and

         * same types of arguments.

         */

        @Override

        public boolean equals(final Object o) {

            if(o instanceof MethodSignature) {

                final MethodSignature ms = (MethodSignature)o;

                return ms.name.equals(name) && Arrays.equals(args, ms.args);

            }

            return false;

        }

        /**

         * Returns a hash code, consistent with the overridden {@link #equals(Object)}.

         */

        @Override

        public int hashCode() {

            return name.hashCode() ^ Arrays.hashCode(args);

        }

        @Override

        public String toString() {

            final StringBuilder b = new StringBuilder();

            b.append("[MethodSignature ").append(name).append('(');

            if(args.length > 0) {

                b.append(args[0].getCanonicalName());

                for(int i = 1; i < args.length; ++i) {

                    b.append(", ").append(args[i].getCanonicalName());

                }

            }

            return b.append(")]").toString();

        }

    }

    private void lookupAccessibleMembers(final Class<?> clazz) {

        boolean searchSuperTypes;

        if(!CheckRestrictedPackage.isRestrictedClass(clazz)) {

            searchSuperTypes = false;

            for(final Method method: clazz.getMethods()) {

                final boolean isStatic = Modifier.isStatic(method.getModifiers());

                if(instance != isStatic) {

                    final MethodSignature sig = new MethodSignature(method);

                    if(!methods.containsKey(sig)) {

                        final Class<?> declaringClass = method.getDeclaringClass();

                        if(declaringClass != clazz && CheckRestrictedPackage.isRestrictedClass(declaringClass)) {

                            //Sometimes, the declaring class of a method (Method.getDeclaringClass())

                            //retrieved through Class.getMethods() for a public class will be a

                            //non-public superclass. For such a method, we need to find a method with

                            //the same name and signature in a public superclass or implemented

                            //interface.

                            //This typically doesn't happen with classes emitted by a reasonably modern

                            //javac, as it'll create synthetic delegator methods in all public

                            //immediate subclasses of the non-public class. We have, however, observed

                            //this in the wild with class files compiled with older javac that doesn't

                            //generate the said synthetic delegators.

                            searchSuperTypes = true;

                        } else {

                            // don't allow inherited static

                            if (!isStatic || clazz == declaringClass) {

                                methods.put(sig, method);

                            }

                        }

                    }

                }

            }

            for(final Class<?> innerClass: clazz.getClasses()) {

                // Add both static and non-static classes, regardless of instance flag. StaticClassLinker will just

                // expose non-static classes with explicit constructor outer class argument.

                // NOTE: getting inner class objects through getClasses() does not resolve them, so if those classes

                // were not yet loaded, they'll only get loaded in a non-resolved state; no static initializers for

                // them will trigger just by doing this.

                innerClasses.add(innerClass);

            }

        } else {

            searchSuperTypes = true;

        }

        // don't need to search super types for static methods

        if(instance && searchSuperTypes) {

            // If we reach here, the class is either not public, or it is in a restricted package. Alternatively, it is

            // public, but some of its methods claim that their declaring class is non-public. We'll try superclasses

            // and implemented interfaces then looking for public ones.

            final Class<?>[] interfaces = clazz.getInterfaces();

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

                lookupAccessibleMembers(interfaces[i]);

            }

            final Class<?> superclass = clazz.getSuperclass();

            if(superclass != null) {

                lookupAccessibleMembers(superclass);

            }

        }

    }

}