/*
 * Copyright (C) 2014 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.systemui.statusbar.phone;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ScrollView;

/**
 * A scroll view which can be observed for scroll change events.
 */
public class ObservableScrollView extends ScrollView {

    private Listener mListener;
    private int mLastOverscrollAmount;

    public ObservableScrollView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public void setListener(Listener listener) {
        mListener = listener;
    }

    public boolean isScrolledToBottom() {
        return getScrollY() == getMaxScrollY();
    }

    private int getMaxScrollY() {
        int scrollRange = 0;
        if (getChildCount() > 0) {
            View child = getChildAt(0);
            scrollRange = Math.max(0,
                    child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop));
        }
        return scrollRange;
    }

    @Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
        super.onScrollChanged(l, t, oldl, oldt);
        if (mListener != null) {
            mListener.onScrollChanged();
        }
    }

    @Override
    protected boolean overScrollBy(int deltaX, int deltaY, int scrollX, int scrollY,
            int scrollRangeX, int scrollRangeY, int maxOverScrollX, int maxOverScrollY,
            boolean isTouchEvent) {
        mLastOverscrollAmount = Math.max(0, scrollY + deltaY - getMaxScrollY());
        return super.overScrollBy(deltaX, deltaY, scrollX, scrollY, scrollRangeX, scrollRangeY,
                        maxOverScrollX, maxOverScrollY, isTouchEvent);
    }

    @Override
    protected void onOverScrolled(int scrollX, int scrollY, boolean clampedX, boolean clampedY) {
        super.onOverScrolled(scrollX, scrollY, clampedX, clampedY);
        if (mListener != null && mLastOverscrollAmount > 0) {
            mListener.onOverscrolled(mLastOverscrollAmount);
        }
    }

    public interface Listener {
        void onScrollChanged();
        void onOverscrolled(int amount);
    }
}