/*

 * 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.util.Iterator;

import java.util.LinkedList;

import java.util.List;

import jdk.dynalink.linker.ConversionComparator.Comparison;

import jdk.dynalink.linker.LinkerServices;

import jdk.dynalink.linker.support.TypeUtilities;

/**

 * Utility class that encapsulates the algorithm for choosing the maximally specific methods.

 */

class MaximallySpecific {

    /**

     * Given a list of methods, returns a list of maximally specific methods.

     *

     * @param methods the list of methods

     * @param varArgs whether to assume the methods are varargs

     * @return the list of maximally specific methods.

     */

    static List<SingleDynamicMethod> getMaximallySpecificMethods(final List<SingleDynamicMethod> methods, final boolean varArgs) {

        return getMaximallySpecificSingleDynamicMethods(methods, varArgs, null, null);

    }

    private abstract static class MethodTypeGetter<T> {

        abstract MethodType getMethodType(T t);

    }

    private static final MethodTypeGetter<MethodHandle> METHOD_HANDLE_TYPE_GETTER =

            new MethodTypeGetter<MethodHandle>() {

        @Override

        MethodType getMethodType(final MethodHandle t) {

            return t.type();

        }

    };

    private static final MethodTypeGetter<SingleDynamicMethod> DYNAMIC_METHOD_TYPE_GETTER =

            new MethodTypeGetter<SingleDynamicMethod>() {

        @Override

        MethodType getMethodType(final SingleDynamicMethod t) {

            return t.getMethodType();

        }

    };

     /**

      * Given a list of methods handles, returns a list of maximally specific methods, applying language-runtime

      * specific conversion preferences.

      *

      * @param methods the list of method handles

      * @param varArgs whether to assume the method handles are varargs

      * @param argTypes concrete argument types for the invocation

      * @return the list of maximally specific method handles.

      */

     static List<MethodHandle> getMaximallySpecificMethodHandles(final List<MethodHandle> methods, final boolean varArgs,

             final Class<?>[] argTypes, final LinkerServices ls) {

         return getMaximallySpecificMethods(methods, varArgs, argTypes, ls, METHOD_HANDLE_TYPE_GETTER);

     }

     /**

      * Given a list of methods, returns a list of maximally specific methods, applying language-runtime specific

      * conversion preferences.

      *

      * @param methods the list of methods

      * @param varArgs whether to assume the methods are varargs

      * @param argTypes concrete argument types for the invocation

      * @return the list of maximally specific methods.

      */

     static List<SingleDynamicMethod> getMaximallySpecificSingleDynamicMethods(final List<SingleDynamicMethod> methods,

             final boolean varArgs, final Class<?>[] argTypes, final LinkerServices ls) {

         return getMaximallySpecificMethods(methods, varArgs, argTypes, ls, DYNAMIC_METHOD_TYPE_GETTER);

     }

    /**

     * Given a list of methods, returns a list of maximally specific methods, applying language-runtime specific

     * conversion preferences.

     *

     * @param methods the list of methods

     * @param varArgs whether to assume the methods are varargs

     * @param argTypes concrete argument types for the invocation

     * @return the list of maximally specific methods.

     */

    private static <T> List<T> getMaximallySpecificMethods(final List<T> methods, final boolean varArgs,

            final Class<?>[] argTypes, final LinkerServices ls, final MethodTypeGetter<T> methodTypeGetter) {

        if(methods.size() < 2) {

            return methods;

        }

        final LinkedList<T> maximals = new LinkedList<>();

        for(final T m: methods) {

            final MethodType methodType = methodTypeGetter.getMethodType(m);

            boolean lessSpecific = false;

            for(final Iterator<T> maximal = maximals.iterator(); maximal.hasNext();) {

                final T max = maximal.next();

                switch(isMoreSpecific(methodType, methodTypeGetter.getMethodType(max), varArgs, argTypes, ls)) {

                    case TYPE_1_BETTER: {

                        maximal.remove();

                        break;

                    }

                    case TYPE_2_BETTER: {

                        lessSpecific = true;

                        break;

                    }

                    case INDETERMINATE: {

                        // do nothing

                        break;

                    }

                    default: {

                        throw new AssertionError();

                    }

                }

            }

            if(!lessSpecific) {

                maximals.addLast(m);

            }

        }

        return maximals;

    }

    private static Comparison isMoreSpecific(final MethodType t1, final MethodType t2, final boolean varArgs, final Class<?>[] argTypes,

            final LinkerServices ls) {

        final int pc1 = t1.parameterCount();

        final int pc2 = t2.parameterCount();

        assert varArgs || (pc1 == pc2) && (argTypes == null || argTypes.length == pc1);

        assert (argTypes == null) == (ls == null);

        final int maxPc = Math.max(Math.max(pc1, pc2), argTypes == null ? 0 : argTypes.length);

        boolean t1MoreSpecific = false;

        boolean t2MoreSpecific = false;

        // NOTE: Starting from 1 as overloaded method resolution doesn't depend on 0th element, which is the type of

        // 'this'. We're only dealing with instance methods here, not static methods. Actually, static methods will have

        // a fake 'this' of type StaticClass.

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

            final Class<?> c1 = getParameterClass(t1, pc1, i, varArgs);

            final Class<?> c2 = getParameterClass(t2, pc2, i, varArgs);

            if(c1 != c2) {

                final Comparison cmp = compare(c1, c2, argTypes, i, ls);

                if(cmp == Comparison.TYPE_1_BETTER && !t1MoreSpecific) {

                    t1MoreSpecific = true;

                    if(t2MoreSpecific) {

                        return Comparison.INDETERMINATE;

                    }

                }

                if(cmp == Comparison.TYPE_2_BETTER && !t2MoreSpecific) {

                    t2MoreSpecific = true;

                    if(t1MoreSpecific) {

                        return Comparison.INDETERMINATE;

                    }

                }

            }

        }

        if(t1MoreSpecific) {

            return Comparison.TYPE_1_BETTER;

        } else if(t2MoreSpecific) {

            return Comparison.TYPE_2_BETTER;

        }

        return Comparison.INDETERMINATE;

    }

    private static Comparison compare(final Class<?> c1, final Class<?> c2, final Class<?>[] argTypes, final int i, final LinkerServices cmp) {

        if(cmp != null) {

            final Comparison c = cmp.compareConversion(argTypes[i], c1, c2);

            if(c != Comparison.INDETERMINATE) {

                return c;

            }

        }

        if(TypeUtilities.isSubtype(c1, c2)) {

            return Comparison.TYPE_1_BETTER;

        } if(TypeUtilities.isSubtype(c2, c1)) {

            return Comparison.TYPE_2_BETTER;

        }

        return Comparison.INDETERMINATE;

    }

    private static Class<?> getParameterClass(final MethodType t, final int l, final int i, final boolean varArgs) {

        return varArgs && i >= l - 1 ? t.parameterType(l - 1).getComponentType() : t.parameterType(i);

    }

}