/*
 * Copyright (c) 2016 wugian
 * 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.xgimi.gimicinema.view;

import android.content.Context;
import android.support.annotation.Nullable;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.widget.Scroller;

/**
 * Created by 李攀 on 2016/9/21
 */
public class OrderRecyclerView extends RecyclerView {
    private static final String TAG = OrderRecyclerView.class.getSimpleName();
    private Scroller mScroller;
    private int mLastx = 0;
    private int mTargetPos;
    //用于设置自动平移时候的速度
    private float mPxPerMillsec = 0;

    public OrderRecyclerView(Context context) {
        super(context);
        init(context);
    }

    public OrderRecyclerView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }

    public OrderRecyclerView(Context context, @Nullable AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init(context);
    }

    private void init(Context context) {
        mScroller = new Scroller(context);
        setChildrenDrawingOrderEnabled(true);
    }

    @Override
    protected int getChildDrawingOrder(int childCount, int i) {
        View view = this.getFocusedChild();
        if (view == null) {
            return i;
        }

        int focusIndex = this.indexOfChild(view);
        if (i < focusIndex) {
            return i;
        } else if (i < childCount - 1) {
            return focusIndex + childCount - 1 - i;
        } else {
            return focusIndex;
        }
    }

    @Override
    public void computeScroll() {
        super.computeScroll();
        //computeScrollOffset返回true表示滚动还在继续，持续时间应该就是startScroll设置的时间
        if (mScroller != null && mScroller.computeScrollOffset()) {
            scrollBy(mLastx - mScroller.getCurrX(), 0);
            mLastx = mScroller.getCurrX();
            postInvalidate();//让系统继续重绘，则会继续重复执行computeScroll
        }
    }

    //调用此方法滚动到目标位置
    public void smoothScrollTo(int fx, int fy, int duration) {
        int dx = 0;
        int dy = 0;
        if (fx != 0) {
            dx = fx - mScroller.getFinalX();
        }
        if (fy != 0) {
            dy = fy - mScroller.getFinalY();
        }
        smoothScrollBy(dx, dy, duration);
    }

    //调用此方法设置滚动的相对偏移
    public void smoothScrollBy(int dx, int dy, int duration) {
        if (duration > 0) {
            mScroller.startScroll(mScroller.getFinalX(), mScroller.getFinalY(), dx, dy, duration);
        } else {
            //设置mScroller的滚动偏移量
            mScroller.startScroll(mScroller.getFinalX(), mScroller.getFinalY(), dx, dy);
        }
        /**
         * 重绘整个view，重绘过程会调用到computeScroll()方法
         */
        invalidate();//这里必须调用invalidate()才能保证computeScroll()会被调用，否则不一定会刷新界面，看不到滚动效果
    }

    public void checkAutoAdjust(int position) {
        int childcount = getChildCount();
        //获取可视范围内的选项的头尾位置
        int firstvisiableposition = ((LinearLayoutManager) getLayoutManager()).findFirstVisibleItemPosition();
        int lastvisiableposition = ((LinearLayoutManager) getLayoutManager()).findLastVisibleItemPosition();
        Log.d(TAG, "childcount:" + childcount + "  position:" + position + "  firstvisiableposition:" + firstvisiableposition
                + "  lastvisiableposition:" + lastvisiableposition);
        if (position == (firstvisiableposition + 1) || position == firstvisiableposition) {
            //当前位置需要向右平移
            leftScrollBy(position, firstvisiableposition);
        } else if (position == (lastvisiableposition - 1) || position == lastvisiableposition) {
            //当前位置需要向做平移
            rightScrollBy(position, lastvisiableposition);
        }
    }

    private void leftScrollBy(int position, int firstvisiableposition) {
        View leftChild = getChildAt(0);
        if (leftChild != null) {
            int leftx = leftChild.getLeft();
            Log.d(TAG, "leftChild left:" + leftx);
            int startleft = leftx;
            int endleft = position == firstvisiableposition ? leftChild.getWidth() : 0;
            autoAdjustScroll(startleft, endleft);
        }
    }


    private void rightScrollBy(int position, int lastvisiableposition) {
        int childcount = getChildCount();
        View rightChild = getChildAt(childcount - 1);
        if (rightChild != null) {
            int rightx = rightChild.getRight();
            int dx = rightx - getWidth();
            Log.d(TAG, "rightChild right:" + rightx + " dx:" + dx);
            int startright = dx;
            int endright = position == lastvisiableposition ? -1 * rightChild.getWidth() : 0;
            autoAdjustScroll(startright, endright);
        }
    }

    /**
     * @param start 滑动起始位置
     * @param end   滑动结束位置
     */
    private void autoAdjustScroll(int start, int end) {
        int duration = 0;
        if (mPxPerMillsec != 0) {
            duration = (int) ((Math.abs(end - start) / mPxPerMillsec));
        }
        mLastx = start;
        if (duration > 0) {
            mScroller.startScroll(start, 0, end - start, 0, duration);
        } else {
            mScroller.startScroll(start, 0, end - start, 0);
        }
        postInvalidate();
    }

    /**
     * 将指定item平滑移动到整个view的中间位置
     *
     * @param position current position
     */
    public void smoothToCenter(int position) {
        /*int parentWidth = getWidth();//获取父视图的宽度
        int childCount = getChildCount();//获取当前视图可见子view的总数
        //获取可视范围内的选项的头尾位置
        int firstVisibleItemPosition = ((LinearLayoutManager) getLayoutManager()).findFirstVisibleItemPosition();
        int lastvisiableposition = ((LinearLayoutManager) getLayoutManager()).findLastVisibleItemPosition();
        int count = ((LinearLayoutManager) getLayoutManager()).getItemCount();//获取item总数
        Log.i(TAG, "count:" + count);
        mTargetPos = Math.max(0, Math.min(count - 1, position));//获取目标item的位置（参考listview中的smoothScrollToPosition方法）
        Log.i(TAG, "firstposition:" + firstVisibleItemPosition + "   lastposition:" + lastvisiableposition + "   position:" + position +
                "   mTargetPos:" + mTargetPos);
        View targetChild = getChildAt(mTargetPos - firstVisibleItemPosition);//获取目标item在当前可见视图item集合中的位置
        View firstChild = getChildAt(0);//当前可见视图集合中的最左view
        View lastChild = getChildAt(childCount - 1);//当前可见视图集合中的最右view
        Log.i(TAG, "first-->left:" + firstChild.getLeft() + "   right:" + firstChild.getRight());
        Log.i(TAG, "last-->left:" + lastChild.getLeft() + "   right:" + lastChild.getRight());
        int childLeftPx = targetChild.getLeft();//子view相对于父view的左边距
        int childRightPx = targetChild.getRight();//子view相对于父view的右边距
        Log.i(TAG, "target-->left:" + targetChild.getLeft() + "   right:" + targetChild.getRight());


        int childWidth = targetChild.getWidth();
        int centerLeft = parentWidth / 2 - childWidth / 2;//计算子view居中后相对于父view的左边距
        int centerRight = parentWidth / 2 + childWidth / 2;//计算子view居中后相对于父view的右边距
        Log.i(TAG, "rv width:" + parentWidth + "   item width:" + childWidth + "   centerleft:" + centerLeft + "   centerRight:" + centerRight);
        if (childLeftPx > centerLeft) {//子view左边距比居中view大（说明子view靠父view的右边，此时需要把子view向左平移
            //平移的起始位置就是子view的左边距，平移的距离就是两者之差
            mLastx = childLeftPx;
            mScroller.startScroll(childLeftPx, 0, centerLeft - childLeftPx, 0, 600);//600为移动时长，可自行设定
            postInvalidate();
        } else if (childRightPx < centerRight) {
            mLastx = childRightPx;
            mScroller.startScroll(childRightPx, 0, centerRight - childRightPx, 0, 600);
            postInvalidate();
        }*/
        int parentWidth = getWidth();//获取父视图的宽度
//        int childCount = getChildCount();//获取当前视图可见子view的总数
        //获取可视范围内的选项的头尾位置
        int firstVisibleItemPosition = ((LinearLayoutManager) getLayoutManager()).findFirstVisibleItemPosition();
        int count = getLayoutManager().getItemCount();//获取item总数
        mTargetPos = Math.max(0, Math.min(count - 1, position));//获取目标item的位置（参考listview中的smoothScrollToPosition方法）
        View targetChild = getChildAt(mTargetPos - firstVisibleItemPosition);//获取目标item在当前可见视图item集合中的位置
        if (targetChild == null) {
            return;
        }
        int childLeftPx = targetChild.getLeft();//子view相对于父view的左边距
        int childRightPx = targetChild.getRight();//子view相对于父view的右边距


        int childWidth = targetChild.getWidth();
        int centerLeft = parentWidth / 2 - childWidth / 2;//计算子view居中后相对于父view的左边距
        int centerRight = parentWidth / 2 + childWidth / 2;//计算子view居中后相对于父view的右边距
        if (childLeftPx > centerLeft) {//子view左边距比居中view大（说明子view靠父view的右边，此时需要把子view向左平移
            //平移的起始位置就是子view的左边距，平移的距离就是两者之差
            mLastx = childLeftPx;
            mScroller.startScroll(childLeftPx, 0, centerLeft - childLeftPx, 0, 600);//600为移动时长，可自行设定
            postInvalidate();
        } else if (childRightPx < centerRight) {
            mLastx = childRightPx;
            mScroller.startScroll(childRightPx, 0, centerRight - childRightPx, 0, 600);
            postInvalidate();
        }
    }
}