/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.ide.eclipse.gltrace.state.transforms;

import com.android.ide.eclipse.gltrace.GLProtoBuf.GLMessage.Function;
import com.android.ide.eclipse.gltrace.state.IGLProperty;

import java.nio.ByteBuffer;

/**
 * A {@link BufferSubDataTransform} updates a portion of the buffer data as specified by
 * the {@link Function#glBufferSubData} function.
 */
public class BufferSubDataTransform implements IStateTransform {
    private final IGLPropertyAccessor mAccessor;
    private final int mOffset;

    private final byte[] mSubData;
    private byte[] mOldData;
    private byte[] mNewData;

    public BufferSubDataTransform(IGLPropertyAccessor accessor, int offset, byte[] data) {
        mAccessor = accessor;
        mOffset = offset;
        mSubData = data;
    }

    @Override
    public void apply(IGLProperty state) {
        IGLProperty property = mAccessor.getProperty(state);
        mOldData = (byte[]) property.getValue();

        if (mOldData != null) {
            mNewData = new byte[mOldData.length];
            ByteBuffer bb = ByteBuffer.wrap(mNewData);

            // copy all of the old buffer
            bb.put(mOldData);
            bb.rewind();

            // update with the sub buffer data at specified offset
            bb.position(mOffset);
            bb.put(mSubData);
        }

        property.setValue(mNewData);
    }

    @Override
    public void revert(IGLProperty state) {
        if (mOldData != null) {
            IGLProperty property = mAccessor.getProperty(state);
            property.setValue(mOldData);
            mOldData = null;
        }
    }

    @Override
    public IGLProperty getChangedProperty(IGLProperty state) {
        return mAccessor.getProperty(state);
    }
}