ValeryPonomarenko

@override
void paint(Canvas canvas, Size size) {
  final center = size.bottomCenter(Offset(0, -dotRadius));

  var radius = startBarRadius;

  for (var layer = 0; layer < layers; layer++) {
    final lengthOfHalfCircle = pi * radius;

    final dotsNumber = (lengthOfHalfCircle / _dotsSizeWithSpacing).floor();

ValeryPonomarenko

@override
void paint(Canvas canvas, Size size) {
  final center = size.bottomCenter(Offset(0, -dotRadius));

  final lengthOfHalfCircle = pi * startBarRadius;

  final dotsNumber = (lengthOfHalfCircle / _dotsSizeWithSpacing).floor();

  final angleStep = _halfCircle / (dotsNumber - 1);
  var angle = _startAngle;

ValeryPonomarenko

class _DiagramPainter extends CustomPainter {
  _DiagramPainter({
    required this.dotRadius,
    required this.startBarRadius,
    required this.layers,
    required this.layersSpacing,
    required this.dotsSpacing,
    required this.progress,
    required Color dotColor,
    required Color progressDotColor,

ValeryPonomarenko

class HalfCircleProgressBar extends StatelessWidget {
  const HalfCircleProgressBar({
    Key? key,
    required this.progress,
    required this.dotColor,
    required this.progressDotColor,
    this.dotRadius = _defaultDotRadius,
    this.startBarRadius = _defaultStartBarRadius,
    this.layers = _defaultLayers,
    this.layersSpacing = _defaultLayersSpacing,

ValeryPonomarenko

class DestinationFragment : Fragment() {

    //code...
    
    @Inject
    internal lateinit var renderer: Renderer<DestinationViewState>

    private val viewModel by lazy { /* code ... */ }

    //code...

ValeryPonomarenko

//EmptyQuery state
class EmptyQueryViewStateRenderer @Inject constructor(): ViewStateRenderer<DestinationViewState> {
    override fun render(view: View, viewState: DestinationViewState) {
        view.text_message.visibility = View.VISIBLE
        view.progress.visibility = View.GONE
        view.recyclerView_destinations.visibility = View.GONE
        view.text_message.text = "Enter the city you want to flight"
    }
}

ValeryPonomarenko

class DestinationViewStateRendererPicker : ViewStateRendererPicker<DestinationViewState> {
    override fun pick(viewState: DestinationViewState): KClass<out ViewStateRenderer<DestinationViewState>> =
        when {
            viewState.query.isBlank() -> EmptyQueryViewStateRenderer::class
            viewState.isLoading -> LoadingViewStateRenderer::class
            viewState.destinations.isEmpty() -> EmptyViewStateRenderer::class
            else -> RegularViewStateRenderer::class
        }
}

ValeryPonomarenko

data class DestinationViewState(
    val destinations: List<SpannableCity> = listOf(),
    val query: String = "",
    val isLoading: Boolean = false
)

ValeryPonomarenko

interface ViewStateRenderer<VS> {
    fun render(view: View, viewState: VS)
}

ValeryPonomarenko

interface ViewStateRendererPicker<VS> {
    fun pick(viewState: VS): KClass<out ViewStateRenderer<VS>>
}