/* Copyright 2022 Tusky Contributors
 *
 * This file is a part of Tusky.
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the
 * GNU General Public License as published by the Free Software Foundation; either version 3 of the
 * License, or (at your option) any later version.
 *
 * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
 * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
 * Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with Tusky; if not,
 * see <http://www.gnu.org/licenses>. */

package com.keylesspalace.tusky.components.account.media

import android.graphics.Rect
import android.view.View
import androidx.recyclerview.widget.RecyclerView
import androidx.recyclerview.widget.RecyclerView.ItemDecoration

class GridSpacingItemDecoration(
    private val spanCount: Int,
    private val spacing: Int,
    private val topOffset: Int
) : ItemDecoration() {

    override fun getItemOffsets(
        outRect: Rect,
        view: View,
        parent: RecyclerView,
        state: RecyclerView.State
    ) {
        val position = parent.getChildAdapterPosition(view) // item position
        if (position < topOffset) return

        val column = (position - topOffset) % spanCount // item column

        outRect.left = column * spacing / spanCount // column * ((1f / spanCount) * spacing)
        outRect.right =
            spacing - (column + 1) * spacing / spanCount // spacing - (column + 1) * ((1f / spanCount) * spacing)
        if (position - topOffset >= spanCount) {
            outRect.top = spacing // item top
        }
    }
}