class FlyingBackgroundView(context: Context, attrs: AttributeSet) : LinearLayout(context, attrs) {

companion object {
    private const val SMOOTH_ANIMATION_DURATION = 10000L
    private const val SCREEN_WIDTH_FACTOR = 3
    private const val SCREEN_HEIGHT_FACTOR = 3
    private const val ICON_SIZE_DP = 60
}

private val iconSubstrateColor = Color.parseColor("#eeeeee")
private val columnContainer: LinearLayout

private val icons = ArrayList<ImageView>()

init {
    val iconSize = dpToPx(ICON_SIZE_DP)
    val iconSubstrateSize = iconSize * 1.5f
    val itemSize = iconSubstrateSize * 1.3f

    val screenMetrics = createDisplayMetrics(context as Activity)
    val screenWidth = screenMetrics.widthPixels
    val screenHeight = screenMetrics.heightPixels

    var columnCount = (screenWidth / itemSize).toInt() * SCREEN_WIDTH_FACTOR
    val itemCount = (screenHeight / itemSize).toInt() * SCREEN_HEIGHT_FACTOR

    if (columnCount.isEven()) columnCount++

    val canvasWidth = columnCount * itemSize.toInt()
    val canvasHeight = itemCount * itemSize.toInt()

    columnContainer = LinearLayout(context)
    columnContainer.layoutParams = LinearLayout.LayoutParams(canvasWidth, canvasHeight)
    columnContainer.clipChildren = false

    for (column in 0 until columnCount) {
        val columnLayout = LinearLayout(context)
        columnLayout.layoutParams = LinearLayout.LayoutParams(itemSize.toInt(),
                ViewGroup.LayoutParams.MATCH_PARENT)
        columnLayout.clipChildren = false
        columnLayout.orientation = VERTICAL
        columnLayout.gravity = Gravity.CENTER

        val countOfItems = if (column.isEven()) itemCount else itemCount - 1
        for (item in 0 until countOfItems) {
            val itemLayout = LinearLayout(context)
            itemLayout.layoutParams = LinearLayout.LayoutParams(itemSize.toInt(), itemSize.toInt())
            itemLayout.gravity = Gravity.CENTER

            val substrateLayout = LinearLayout(context)
            substrateLayout.layoutParams = LinearLayout.LayoutParams(iconSubstrateSize.toInt(),
                    iconSubstrateSize.toInt())
            substrateLayout.gravity = Gravity.CENTER
            val circleBackground = GradientDrawable()
            circleBackground.shape = GradientDrawable.OVAL
            circleBackground.setColor(iconSubstrateColor)
            substrateLayout.placeBackgroundDrawable(circleBackground)

            val iconView = ImageView(context)
            iconView.layoutParams = LinearLayout.LayoutParams(iconSize, iconSize)
            icons.add(iconView)

            substrateLayout.addView(iconView)
            itemLayout.addView(substrateLayout)
            columnLayout.addView(itemLayout)
        }
        columnContainer.addView(columnLayout)
    }

    val centerX = canvasWidth / SCREEN_WIDTH_FACTOR
    val centerY = canvasHeight / SCREEN_HEIGHT_FACTOR
    columnContainer.x = -centerX.toFloat()
    columnContainer.y = -centerY.toFloat()
    addView(columnContainer)

    (object : Runnable {
        override fun run() {
            val maxX = canvasWidth / SCREEN_WIDTH_FACTOR * (SCREEN_WIDTH_FACTOR - 1)
            val maxY = canvasHeight / SCREEN_HEIGHT_FACTOR * (SCREEN_HEIGHT_FACTOR - 1)
            val randomX = Random().nextInt(maxX)
            val randomY = Random().nextInt(maxY)

            ViewCompat.animate(columnContainer)
                    .x(-randomX.toFloat())
                    .y(-randomY.toFloat())
                    .setDuration(SMOOTH_ANIMATION_DURATION)
                    .withEndAction(this)
                    .start()
        }
    }).run()
}

fun setIcon(@DrawableRes iconResId: Int) {
    icons.forEach { icon ->
        ViewCompat.animate(icon)
                .scaleX(0f)
                .scaleY(0f)
                .alpha(0f)
                .setDuration(1000).withEndAction {
                    icon.setImageResource(iconResId)
                    ViewCompat.animate(icon)
                            .scaleX(1f)
                            .scaleY(1f)
                            .alpha(1f)
                            .setDuration(1000)
                            .start()
                }.start()
    }
}