/*

 * Copyright (c) 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.

 */

package com.sun.tools.classfile;

import java.util.ArrayList;

import java.util.HashSet;

import java.util.List;

import java.util.Objects;

import java.util.Set;

import com.sun.tools.classfile.Instruction.TypeKind;

import static com.sun.tools.classfile.ConstantPool.*;

/**

 * A utility class to find where in a ClassFile references

 * a {@link CONSTANT_Methodref_info method},

 * a {@link CONSTANT_InterfaceMethodref_info interface method},

 * or a {@link CONSTANT_Fieldref_info field}.

 */

public final class ReferenceFinder {

    /**

     * Filter for ReferenceFinder of what constant pool entries for reference lookup.

     */

    public interface Filter {

        /**

         * Decides if the given CPRefInfo entry should be accepted or filtered.

         *

         * @param cpool  ConstantPool of the ClassFile being parsed

         * @param cpref  constant pool entry representing a reference to

         *               a fields method, and interface method.

         * @return {@code true} if accepted; otherwise {@code false}

         */

        boolean accept(ConstantPool cpool, CPRefInfo cpref);

    }

    /**

     * Visitor of individual method of a ClassFile that references the

     * accepted field, method, or interface method references.

     */

    public interface Visitor {

        /**

         * Invoked for a method containing one or more accepted CPRefInfo entries

         *

         * @param cf      ClassFile

         * @param method  Method that does the references the accepted references

         * @param refs    Accepted constant pool method/field reference

         */

        void visit(ClassFile cf, Method method, List<CPRefInfo> refConstantPool);

    }

    private final Filter filter;

    private final Visitor visitor;

    /**

     * Constructor.

     */

    public ReferenceFinder(Filter filter, Visitor visitor) {

        this.filter = Objects.requireNonNull(filter);

        this.visitor = Objects.requireNonNull(visitor);

    }

    /**

     * Parses a given ClassFile and invoke the visitor if there is any reference

     * to the constant pool entries referencing field, method, or

     * interface method that are accepted. This method will return

     * {@code true} if there is one or more accepted constant pool entries

     * to lookup; otherwise, it will return {@code false}.

     *

     * @param  cf  ClassFile

     * @return {@code true} if the given class file is processed to lookup

     *         references

     * @throws ConstantPoolException if an error of the constant pool

     */

    public boolean parse(ClassFile cf) throws ConstantPoolException {

        List<Integer> cprefs = new ArrayList<>();

        int index = 1;

        for (ConstantPool.CPInfo cpInfo : cf.constant_pool.entries()) {

            if (cpInfo.accept(cpVisitor, cf.constant_pool)) {

                cprefs.add(index);

            }

            index += cpInfo.size();

        }

        if (cprefs.isEmpty()) {

            return false;

        }

        for (Method m : cf.methods) {

            Set<Integer> ids = new HashSet<>();

            Code_attribute c_attr = (Code_attribute) m.attributes.get(Attribute.Code);

            if (c_attr != null) {

                for (Instruction instr : c_attr.getInstructions()) {

                    int idx = instr.accept(codeVisitor, cprefs);

                    if (idx > 0) {

                        ids.add(idx);

                    }

                }

            }

            if (ids.size() > 0) {

                List<CPRefInfo> refInfos = new ArrayList<>(ids.size());

                for (int id : ids) {

                    refInfos.add(CPRefInfo.class.cast(cf.constant_pool.get(id)));

                }

                visitor.visit(cf, m, refInfos);

            }

        }

        return true;

    }

    private ConstantPool.Visitor<Boolean,ConstantPool> cpVisitor =

            new ConstantPool.Visitor<Boolean,ConstantPool>()

    {

        public Boolean visitClass(CONSTANT_Class_info info, ConstantPool cpool) {

            return false;

        }

        public Boolean visitFieldref(CONSTANT_Fieldref_info info, ConstantPool cpool) {

            return filter.accept(cpool, info);

        }

        public Boolean visitDouble(CONSTANT_Double_info info, ConstantPool cpool) {

            return false;

        }

        public Boolean visitFloat(CONSTANT_Float_info info, ConstantPool cpool) {

            return false;

        }

        public Boolean visitInteger(CONSTANT_Integer_info info, ConstantPool cpool) {

            return false;

        }

        public Boolean visitInterfaceMethodref(CONSTANT_InterfaceMethodref_info info, ConstantPool cpool) {

            return filter.accept(cpool, info);

        }

        public Boolean visitInvokeDynamic(CONSTANT_InvokeDynamic_info info, ConstantPool cpool) {

            return false;

        }

        public Boolean visitLong(CONSTANT_Long_info info, ConstantPool cpool) {

            return false;

        }

        public Boolean visitMethodHandle(CONSTANT_MethodHandle_info info, ConstantPool cpool) {

            return false;

        }

        public Boolean visitMethodref(CONSTANT_Methodref_info info, ConstantPool cpool) {

            return filter.accept(cpool, info);

        }

        public Boolean visitMethodType(CONSTANT_MethodType_info info, ConstantPool cpool) {

            return false;

        }

        public Boolean visitModule(CONSTANT_Module_info info, ConstantPool cpool) {

            return false;

        }

        public Boolean visitNameAndType(CONSTANT_NameAndType_info info, ConstantPool cpool) {

            return false;

        }

        public Boolean visitPackage(CONSTANT_Package_info info, ConstantPool cpool) {

            return false;

        }

        public Boolean visitString(CONSTANT_String_info info, ConstantPool cpool) {

            return false;

        }

        public Boolean visitUtf8(CONSTANT_Utf8_info info, ConstantPool cpool) {

            return false;

        }

    };

    private Instruction.KindVisitor<Integer, List<Integer>> codeVisitor =

            new Instruction.KindVisitor<Integer, List<Integer>>()

    {

        public Integer visitNoOperands(Instruction instr, List<Integer> p) {

            return 0;

        }

        public Integer visitArrayType(Instruction instr, TypeKind kind, List<Integer> p) {

            return 0;

        }

        public Integer visitBranch(Instruction instr, int offset, List<Integer> p) {

            return 0;

        }

        public Integer visitConstantPoolRef(Instruction instr, int index, List<Integer> p) {

            return p.contains(index) ? index : 0;

        }

        public Integer visitConstantPoolRefAndValue(Instruction instr, int index, int value, List<Integer> p) {

            return p.contains(index) ? index : 0;

        }

        public Integer visitLocal(Instruction instr, int index, List<Integer> p) {

            return 0;

        }

        public Integer visitLocalAndValue(Instruction instr, int index, int value, List<Integer> p) {

            return 0;

        }

        public Integer visitLookupSwitch(Instruction instr, int default_, int npairs, int[] matches, int[] offsets, List<Integer> p) {

            return 0;

        }

        public Integer visitTableSwitch(Instruction instr, int default_, int low, int high, int[] offsets, List<Integer> p) {

            return 0;

        }

        public Integer visitValue(Instruction instr, int value, List<Integer> p) {

            return 0;

        }

        public Integer visitUnknown(Instruction instr, List<Integer> p) {

            return 0;

        }

    };

}