/*

 * Copyright (c) 2014, 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.

 *

 * 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 org.graalvm.compiler.core.common;

import static org.graalvm.compiler.core.common.UnsafeAccess.UNSAFE;

import java.lang.reflect.Field;

import java.lang.reflect.Modifier;

import java.util.ArrayList;

import sun.misc.Unsafe;

/**

 * Scans the fields in a class hierarchy.

 */

public class FieldsScanner {

    /**

     * Determines the offset (in bytes) of a field.

     */

    public interface CalcOffset {

        long getOffset(Field field);

    }

    /**

     * Determines the offset (in bytes) of a field using {@link Unsafe#objectFieldOffset(Field)}.

     */

    public static class DefaultCalcOffset implements CalcOffset {

        @Override

        public long getOffset(Field field) {

            return UNSAFE.objectFieldOffset(field);

        }

    }

    /**

     * Describes a field in a class during {@linkplain FieldsScanner scanning}.

     */

    public static class FieldInfo implements Comparable<FieldInfo> {

        public final long offset;

        public final String name;

        public final Class<?> type;

        public final Class<?> declaringClass;

        public FieldInfo(long offset, String name, Class<?> type, Class<?> declaringClass) {

            this.offset = offset;

            this.name = name;

            this.type = type;

            this.declaringClass = declaringClass;

        }

        /**

         * Sorts fields in ascending order by their {@link #offset}s.

         */

        @Override

        public int compareTo(FieldInfo o) {

            return offset < o.offset ? -1 : (offset > o.offset ? 1 : 0);

        }

        @Override

        public String toString() {

            return "[" + offset + "]" + name + ":" + type.getSimpleName();

        }

    }

    private final FieldsScanner.CalcOffset calc;

    /**

     * Fields not belonging to a more specific category defined by scanner subclasses are added to

     * this list.

     */

    public final ArrayList<FieldsScanner.FieldInfo> data = new ArrayList<>();

    public FieldsScanner(FieldsScanner.CalcOffset calc) {

        this.calc = calc;

    }

    /**

     * Scans the fields in a class hierarchy.

     *

     * @param clazz the class at which to start scanning

     * @param endClazz scanning stops when this class is encountered (i.e. {@code endClazz} is not

     *            scanned)

     */

    public void scan(Class<?> clazz, Class<?> endClazz, boolean includeTransient) {

        Class<?> currentClazz = clazz;

        while (currentClazz != endClazz) {

            for (Field field : currentClazz.getDeclaredFields()) {

                if (Modifier.isStatic(field.getModifiers())) {

                    continue;

                }

                if (!includeTransient && Modifier.isTransient(field.getModifiers())) {

                    continue;

                }

                long offset = calc.getOffset(field);

                scanField(field, offset);

            }

            currentClazz = currentClazz.getSuperclass();

        }

    }

    protected void scanField(Field field, long offset) {

        data.add(new FieldsScanner.FieldInfo(offset, field.getName(), field.getType(), field.getDeclaringClass()));

    }

}