package com.sensetime.demo.view;

import android.graphics.Rect;
import android.view.View;

import androidx.recyclerview.widget.RecyclerView;

/**
 * @Version V1.0.0
 * Author:Created by LaoTie on 2019/12/13.
 **/
public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {

    private int spanCount;
    private int spacing;
    private int bottomSpacing;
    private int topSpacing;
    private boolean includeEdge;

    public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge, int topSpacing, int bottomSpacing) {
        this.spanCount = spanCount;
        this.spacing = spacing;
        this.includeEdge = includeEdge;
        this.topSpacing = topSpacing;
        this.bottomSpacing = bottomSpacing;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildAdapterPosition(view); // item position
        int column = position % spanCount; // item column

        if (includeEdge) {
            outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
            outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)

            if (position < spanCount) { // top edge
                outRect.top = spacing;
            }
            outRect.bottom = spacing; // item bottom
        } else {
            outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
            outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
            if (position >= spanCount) {
                outRect.top = spacing; // item top
            }
        }
        if (position < spanCount) {
            outRect.top = topSpacing;
        }
        int totalCount = parent.getAdapter().getItemCount();
        int pos = totalCount - (totalCount % spanCount == 0 ? spanCount : totalCount % spanCount) - 1;
        if (position > pos) {
            outRect.bottom = bottomSpacing;
        }
    }
}
