/*
 * Copyright (c) 2024, 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
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 */

package java.io;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;

import jdk.internal.access.JavaObjectStreamReflectionAccess;
import jdk.internal.access.SharedSecrets;
import jdk.internal.util.ByteArray;

/**
 * Utilities relating to serialization and deserialization of objects.
 */
final class ObjectStreamReflection {

    // todo: these could be constants
    private static final MethodHandle DRO_HANDLE;
    private static final MethodHandle DWO_HANDLE;

    static {
        try {
            MethodHandles.Lookup lookup = MethodHandles.lookup();
            MethodType droType = MethodType.methodType(void.class, ObjectStreamClass.class, Object.class, ObjectInputStream.class);
            DRO_HANDLE = lookup.findStatic(ObjectStreamReflection.class, "defaultReadObject", droType);
            MethodType dwoType = MethodType.methodType(void.class, ObjectStreamClass.class, Object.class, ObjectOutputStream.class);
            DWO_HANDLE = lookup.findStatic(ObjectStreamReflection.class, "defaultWriteObject", dwoType);
        } catch (NoSuchMethodException | IllegalAccessException e) {
            throw new InternalError(e);
        }
    }

    /**
     * Populate a serializable object from data acquired from the stream's
     * {@link java.io.ObjectInputStream.GetField} object independently of
     * the actual {@link ObjectInputStream} implementation which may
     * arbitrarily override the {@link ObjectInputStream#readFields()} method
     * in order to deserialize using a custom object format.
     * <p>
     * The fields are populated using the mechanism defined in {@link ObjectStreamClass},
     * which requires objects and primitives to each be packed into a separate array
     * whose relative field offsets are defined in the {@link ObjectStreamField}
     * corresponding to each field.
     * Utility methods on the {@code ObjectStreamClass} instance are then used
     * to validate and perform the actual field accesses.
     *
     * @param streamClass the object stream class of the object (must not be {@code null})
     * @param obj the object to deserialize (must not be {@code null})
     * @param ois the object stream (must not be {@code null})
     * @throws IOException if the call to {@link ObjectInputStream#readFields}
     *                     or one of its field accessors throws this exception type
     * @throws ClassNotFoundException if the call to {@link ObjectInputStream#readFields}
     *                                or one of its field accessors throws this exception type
     */
    private static void defaultReadObject(ObjectStreamClass streamClass, Object obj, ObjectInputStream ois)
            throws IOException, ClassNotFoundException {
        ObjectInputStream.GetField getField = ois.readFields();
        byte[] bytes = new byte[streamClass.getPrimDataSize()];
        Object[] objs = new Object[streamClass.getNumObjFields()];
        for (ObjectStreamField field : streamClass.getFields(false)) {
            int offset = field.getOffset();
            String fieldName = field.getName();
            switch (field.getTypeCode()) {
                case 'B' -> bytes[offset] = getField.get(fieldName, (byte) 0);
                case 'C' -> ByteArray.setChar(bytes, offset, getField.get(fieldName, (char) 0));
                case 'D' -> ByteArray.setDoubleRaw(bytes, offset, getField.get(fieldName, 0.0));
                case 'F' -> ByteArray.setFloatRaw(bytes, offset, getField.get(fieldName, 0.0f));
                case 'I' -> ByteArray.setInt(bytes, offset, getField.get(fieldName, 0));
                case 'J' -> ByteArray.setLong(bytes, offset, getField.get(fieldName, 0L));
                case 'S' -> ByteArray.setShort(bytes, offset, getField.get(fieldName, (short) 0));
                case 'Z' -> ByteArray.setBoolean(bytes, offset, getField.get(fieldName, false));
                case '[', 'L' -> objs[offset] = getField.get(fieldName, null);
                default -> throw new IllegalStateException();
            }
        }
        streamClass.checkObjFieldValueTypes(obj, objs);
        streamClass.setPrimFieldValues(obj, bytes);
        streamClass.setObjFieldValues(obj, objs);
    }

    /**
     * Populate and write a stream's {@link java.io.ObjectOutputStream.PutField} object
     * from field data acquired from a serializable object independently of
     * the actual {@link ObjectOutputStream} implementation which may
     * arbitrarily override the {@link ObjectOutputStream#putFields()}
     * and {@link ObjectOutputStream#writeFields()} methods
     * in order to deserialize using a custom object format.
     * <p>
     * The fields are accessed using the mechanism defined in {@link ObjectStreamClass},
     * which causes objects and primitives to each be packed into a separate array
     * whose relative field offsets are defined in the {@link ObjectStreamField}
     * corresponding to each field.
     *
     * @param streamClass the object stream class of the object (must not be {@code null})
     * @param obj the object to serialize (must not be {@code null})
     * @param oos the object stream (must not be {@code null})
     * @throws IOException if the call to {@link ObjectInputStream#readFields}
     *                     or one of its field accessors throws this exception type
     */
    private static void defaultWriteObject(ObjectStreamClass streamClass, Object obj, ObjectOutputStream oos)
            throws IOException {
        ObjectOutputStream.PutField putField = oos.putFields();
        byte[] bytes = new byte[streamClass.getPrimDataSize()];
        Object[] objs = new Object[streamClass.getNumObjFields()];
        streamClass.getPrimFieldValues(obj, bytes);
        streamClass.getObjFieldValues(obj, objs);
        for (ObjectStreamField field : streamClass.getFields(false)) {
            int offset = field.getOffset();
            String fieldName = field.getName();
            switch (field.getTypeCode()) {
                case 'B' -> putField.put(fieldName, bytes[offset]);
                case 'C' -> putField.put(fieldName, ByteArray.getChar(bytes, offset));
                case 'D' -> putField.put(fieldName, ByteArray.getDouble(bytes, offset));
                case 'F' -> putField.put(fieldName, ByteArray.getFloat(bytes, offset));
                case 'I' -> putField.put(fieldName, ByteArray.getInt(bytes, offset));
                case 'J' -> putField.put(fieldName, ByteArray.getLong(bytes, offset));
                case 'S' -> putField.put(fieldName, ByteArray.getShort(bytes, offset));
                case 'Z' -> putField.put(fieldName, ByteArray.getBoolean(bytes, offset));
                case '[', 'L' -> putField.put(fieldName, objs[offset]);
                default -> throw new IllegalStateException();
            }
        }
        oos.writeFields();
    }

    static final class Access implements JavaObjectStreamReflectionAccess {
        static {
            SharedSecrets.setJavaObjectStreamReflectionAccess(new Access());
        }

        public MethodHandle defaultReadObject(Class<?> clazz) {
            return handleForClass(DRO_HANDLE, clazz, ObjectInputStream.class);
        }

        public MethodHandle defaultWriteObject(Class<?> clazz) {
            return handleForClass(DWO_HANDLE, clazz, ObjectOutputStream.class);
        }

        private static MethodHandle handleForClass(final MethodHandle handle, final Class<?> clazz, final Class<?> ioClass) {
            ObjectStreamClass streamClass = ObjectStreamClass.lookup(clazz);
            if (streamClass != null) {
                try {
                    streamClass.checkDefaultSerialize();
                    return handle.bindTo(streamClass)
                        .asType(MethodType.methodType(void.class, clazz, ioClass));
                } catch (InvalidClassException e) {
                    // ignore and return null
                }
            }
            return null;
        }
    }
}