/*
 * 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.state.GLListProperty;
import com.android.ide.eclipse.gltrace.state.IGLProperty;

/**
 * A {@link ListElementAddTransform} provides the ability to add a new property to a list of
 * properties in the GL State.
 */
public class ListElementAddTransform implements IStateTransform {
    private final IGLPropertyAccessor mAccessor;
    private final IGLProperty mElement;

    public ListElementAddTransform(IGLPropertyAccessor accessor, IGLProperty element) {
        mAccessor = accessor;
        mElement = element;
    }

    @Override
    public void apply(IGLProperty currentState) {
        GLListProperty list = getList(currentState);
        if (list != null) {
            list.add(mElement);
        }
    }

    @Override
    public void revert(IGLProperty currentState) {
        GLListProperty list = getList(currentState);
        if (list != null) {
            list.remove(mElement);
        }
    }

    @Override
    public IGLProperty getChangedProperty(IGLProperty currentState) {
        return getList(currentState);
    }

    private GLListProperty getList(IGLProperty state) {
        IGLProperty p = state;

        if (mAccessor != null) {
            p = mAccessor.getProperty(p);
        }

        if (p instanceof GLListProperty) {
            return (GLListProperty) p;
        } else {
            return null;
        }
    }
}