import android.content.Context
import android.graphics.PointF
import android.support.v7.widget.LinearLayoutManager
import android.support.v7.widget.LinearSmoothScroller
import android.support.v7.widget.RecyclerView


class SmoothScrollableLinearLayoutManager @JvmOverloads constructor(context: Context, orientation: Int = LinearLayoutManager.VERTICAL, reverseLayout: Boolean = false) : LinearLayoutManager(context, orientation, reverseLayout) {

    override fun smoothScrollToPosition(recyclerView: RecyclerView, state: RecyclerView.State, position: Int) {
        startSmoothScroll(TopSnappedSmoothScroller(recyclerView.context).apply {
            targetPosition = position
        })
    }

    private inner class TopSnappedSmoothScroller(context: Context) : LinearSmoothScroller(context) {

        override fun computeScrollVectorForPosition(targetPosition: Int): PointF {
            return this@SmoothScrollableLinearLayoutManager.computeScrollVectorForPosition(targetPosition)
        }

        override fun getVerticalSnapPreference(): Int = SNAP_TO_START
    }
}