SpacedItemDecoration

package app.pengadaan.helper

import android.graphics.Rect
import android.view.View
import androidx.recyclerview.widget.GridLayoutManager
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import androidx.recyclerview.widget.StaggeredGridLayoutManager
import kotlin.math.roundToInt

class SpacedItemDecoration : RecyclerView.ItemDecoration {

    private var space = 0
    private var mView : View? = null

    constructor()
    constructor(space: Int) : super() {
        this.space = space
    }

    override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
        super.getItemOffsets(outRect, view, parent, state)
        mView = view
        val rvLayoutManager = parent.layoutManager
        val rvItemCount = state.itemCount
        val adapterItemCount = parent.adapter?.itemCount ?: 0
        var itemPosition = parent.getChildAdapterPosition(view)
        if(rvItemCount > adapterItemCount){
            if(itemPosition == 0){
                return
            }else{
                itemPosition -= 1
            }
        }

        if (rvLayoutManager is GridLayoutManager) {
            setItemGridOffset(outRect, rvLayoutManager.orientation, rvLayoutManager.spanCount, adapterItemCount, itemPosition)
        } else if (rvLayoutManager is StaggeredGridLayoutManager) {
            setItemStaggeredGridOffset(outRect, rvLayoutManager.orientation, rvLayoutManager.spanCount, adapterItemCount, itemPosition)
        } else if (rvLayoutManager is LinearLayoutManager) {
            setItemLinearOffset(outRect, rvLayoutManager.orientation, itemPosition)
        }
    }

    private fun setItemGridOffset(outRect: Rect, layoutOrientation: Int, spanCount: Int, adapterItemCount: Int, itemPosition: Int){
        val position = itemPosition + 1
        val divideByTwo = space/2
        if(layoutOrientation == GridLayoutManager.VERTICAL){
            if(position.rem(spanCount) != 0){
                outRect.right = divideByTwo
            }else{
                outRect.left = divideByTwo
            }

            if((adapterItemCount.rem(spanCount) != 0 && position < adapterItemCount)
                    || (adapterItemCount.rem(spanCount) == 0 && position <= (adapterItemCount - spanCount))){ // Not in the last row
                outRect.bottom = space
            }
        }else{
            if(position.rem(spanCount) != 0){
                outRect.bottom = divideByTwo
            }else{
                outRect.top = divideByTwo
            }

            if((adapterItemCount.rem(spanCount) != 0 && position < adapterItemCount)
                    || (adapterItemCount.rem(spanCount) == 0 && position <= (adapterItemCount - spanCount))){ // Not in the last column
                outRect.right = space
            }
        }
    }

    private fun setItemLinearOffset(outRect: Rect, layoutOrientation: Int, itemPosition: Int){
        if(layoutOrientation == GridLayoutManager.VERTICAL){
            if(itemPosition == 0) {
                val littleSpare = (space * 0.5).roundToInt()
                outRect.top = space + littleSpare
            } else {
                outRect.top = space
            }
        }else{
            if(itemPosition == 0) {
                return
            }
            outRect.left = space
        }
    }

    private fun setItemStaggeredGridOffset(outRect: Rect, layoutOrientation: Int, spanCount: Int, itemCount: Int, childLayoutPosition: Int){
        val position = childLayoutPosition + 1
        val layoutParams = mView?.layoutParams as StaggeredGridLayoutManager.LayoutParams
        val spanIndex = layoutParams.spanIndex
        val divideByTwo = space/2
        if(layoutOrientation == GridLayoutManager.VERTICAL){
            if(spanIndex == 1){
                outRect.left = divideByTwo;
            } else{
                outRect.right = divideByTwo;
            }

            if((itemCount.rem(spanCount) != 0 && position < itemCount)
                    || (itemCount.rem(spanCount) == 0 && position <= (itemCount - spanCount))){ // Not in the last row
                outRect.bottom = space
            }
        }else{
            if(spanIndex == 1){
                outRect.bottom = divideByTwo;
            } else{
                outRect.top = divideByTwo;
            }

            if((itemCount.rem(spanCount) != 0 && position < itemCount)
                    || (itemCount.rem(spanCount) == 0 && position <= (itemCount - spanCount))){ // Not in the last column
                outRect.right = space
            }
        }
    }
}