Kotlin: Implement filtering by date from openhistoricalmap

[nitanmarcel]

I'm trying to implement date filtering from a maplibre js implementation from openhistorymap to kotlin but I can't get to make it work properly. I'm stuck on either the filtering not working at all, or some countries names not being removed

@HiltViewModel
class MapViewModel @Inject constructor(
    private val settingsDataStore: SettingsDataStore
) : ViewModel() {

    val dateRange = settingsDataStore.dateRange

    fun filterLayersByDate(map: MapLibreMap, date: Date) {
        val dateRange = DateRange.fromDate(date)
        val style = map.style

        for (layer in style?.layers!!) {
            when (layer) {
                is LineLayer -> {
                    layer.setFilter(
                        constrainExpressionFilterByDateRange(layer.filter, dateRange)
                    )
                }
                is FillLayer -> {
                    layer.setFilter(
                        constrainExpressionFilterByDateRange(layer.filter, dateRange)
                    )
                }
                is CircleLayer -> {
                    layer.setFilter(
                        constrainExpressionFilterByDateRange(layer.filter, dateRange)
                    )
                }
                is SymbolLayer -> {
                    layer.setFilter(
                        constrainExpressionFilterByDateRange(layer.filter, dateRange)
                    )
                }
                is HeatmapLayer -> {
                    layer.setFilter(
                        constrainExpressionFilterByDateRange(layer.filter, dateRange)
                    )
                }
                is FillExtrusionLayer -> {
                    layer.setFilter(
                        constrainExpressionFilterByDateRange(layer.filter, dateRange)
                    )
                }
                else -> {
                }
            }
        }
    }

    private fun constrainExpressionFilterByDateRange(
        filter: Expression? = null,
        dateRange: DateRange,
        variablePrefix: String = "maplibre_gl_dates"
    ): Expression {
        val startDecimalYearVariable = "${variablePrefix}__startDecimalYear"
        val startISODateVariable = "${variablePrefix}__startISODate"
        val endDecimalYearVariable = "${variablePrefix}__endDecimalYear"
        val endISODateVariable = "${variablePrefix}__endISODate"

        val dateConstraints = Expression.all(
            Expression.any(
                Expression.all(
                    Expression.has("start_decdate"),
                    Expression.lt(
                        Expression.get("start_decdate"),
                        Expression.`var`(endDecimalYearVariable)
                    )
                ),
                Expression.all(
                    Expression.not(Expression.has("start_decdate")),
                    Expression.has("start_date"),
                    Expression.lt(
                        Expression.get("start_date"),
                        Expression.`var`(endISODateVariable)
                    )
                ),
                Expression.all(
                    Expression.not(Expression.has("start_decdate")),
                    Expression.not(Expression.has("start_date"))
                )
            ),
            Expression.any(
                Expression.all(
                    Expression.has("end_decdate"),
                    Expression.gte(
                        Expression.get("end_decdate"),
                        Expression.`var`(startDecimalYearVariable)
                    )
                ),
                Expression.all(
                    Expression.not(Expression.has("end_decdate")),
                    Expression.has("end_date"),
                    Expression.gte(
                        Expression.get("end_date"),
                        Expression.`var`(startISODateVariable)
                    )
                ),
                Expression.all(
                    Expression.not(Expression.has("end_decdate")),
                    Expression.not(Expression.has("end_date"))
                )
            )
        )

        val finalExpression = if (filter != null) {
            Expression.all(dateConstraints, filter)
        } else {
            dateConstraints
        }

        return Expression.let(
            Expression.literal(startDecimalYearVariable), Expression.literal(dateRange.startDecimalYear),
            Expression.let(
                Expression.literal(startISODateVariable), Expression.literal(dateRange.startDecimalYear),
                Expression.let(
                    Expression.literal(endDecimalYearVariable), Expression.literal(dateRange.endDecimalYear),
                    Expression.let(
                        Expression.literal(endISODateVariable), Expression.literal(dateRange.endDecimalYear),
                        finalExpression
                    )
                )
            )
        )
    }

    fun updateDateRange(newDateRange: DateRange) {
        viewModelScope.launch {
            settingsDataStore.updateDateRange(newDateRange)
        }
    }
}

The js implementation can be found here

https://github.com/OpenHistoricalMap/maplibre-gl-dates/blob/main/index.js