Code cleanup and deduplication pass through weatherfeeder

internal/normalizers/nws/forecast.go

@@ -75,62 +75,63 @@ func normalizeNarrativeForecastEvent(in event.Event) (*event.Event, error) {
 	)
 }
 
+type forecastPeriodMapper[T any] func(idx int, period T) (model.WeatherForecastPeriod, error)
+
 // buildHourlyForecast contains hourly forecast mapping logic (provider -> canonical model).
 func buildHourlyForecast(parsed nwsHourlyForecastResponse) (model.WeatherForecastRun, time.Time, error) {
-	issuedAt, updatedAt, err := parseForecastRunTimes(parsed.Properties.GeneratedAt, parsed.Properties.UpdateTime)
-	if err != nil {
-		return model.WeatherForecastRun{}, time.Time{}, err
-	}
-
-	// Best-effort location centroid from the GeoJSON polygon (optional).
-	lat, lon := centroidLatLon(parsed.Geometry.Coordinates)
-
-	run := newForecastRunBase(
-		issuedAt,
-		updatedAt,
-		model.ForecastProductHourly,
-		lat,
-		lon,
+	return buildForecastRun(
+		parsed.Properties.GeneratedAt,
+		parsed.Properties.UpdateTime,
+		parsed.Geometry.Coordinates,
 		parsed.Properties.Elevation.Value,
+		model.ForecastProductHourly,
+		parsed.Properties.Periods,
+		mapHourlyForecastPeriod,
 	)
-
-	periods := make([]model.WeatherForecastPeriod, 0, len(parsed.Properties.Periods))
-	for i, p := range parsed.Properties.Periods {
-		period, err := mapHourlyForecastPeriod(i, p)
-		if err != nil {
-			return model.WeatherForecastRun{}, time.Time{}, err
-		}
-		periods = append(periods, period)
-	}
-
-	run.Periods = periods
-
-	// EffectiveAt policy for forecasts: treat IssuedAt as the effective time (dedupe-friendly).
-	return run, issuedAt, nil
 }
 
 // buildNarrativeForecast contains narrative forecast mapping logic (provider -> canonical model).
 func buildNarrativeForecast(parsed nwsNarrativeForecastResponse) (model.WeatherForecastRun, time.Time, error) {
-	issuedAt, updatedAt, err := parseForecastRunTimes(parsed.Properties.GeneratedAt, parsed.Properties.UpdateTime)
+	return buildForecastRun(
+		parsed.Properties.GeneratedAt,
+		parsed.Properties.UpdateTime,
+		parsed.Geometry.Coordinates,
+		parsed.Properties.Elevation.Value,
+		model.ForecastProductNarrative,
+		parsed.Properties.Periods,
+		mapNarrativeForecastPeriod,
+	)
+}
+
+func buildForecastRun[T any](
+	generatedAt string,
+	updateTime string,
+	coordinates [][][]float64,
+	elevation *float64,
+	product model.ForecastProduct,
+	srcPeriods []T,
+	mapPeriod forecastPeriodMapper[T],
+) (model.WeatherForecastRun, time.Time, error) {
+	issuedAt, updatedAt, err := parseForecastRunTimes(generatedAt, updateTime)
 	if err != nil {
 		return model.WeatherForecastRun{}, time.Time{}, err
 	}
 
 	// Best-effort location centroid from the GeoJSON polygon (optional).
-	lat, lon := centroidLatLon(parsed.Geometry.Coordinates)
+	lat, lon := centroidLatLon(coordinates)
 
 	run := newForecastRunBase(
 		issuedAt,
 		updatedAt,
-		model.ForecastProductNarrative,
+		product,
 		lat,
 		lon,
-		parsed.Properties.Elevation.Value,
+		elevation,
 	)
 
-	periods := make([]model.WeatherForecastPeriod, 0, len(parsed.Properties.Periods))
-	for i, p := range parsed.Properties.Periods {
-		period, err := mapNarrativeForecastPeriod(i, p)
+	periods := make([]model.WeatherForecastPeriod, 0, len(srcPeriods))
+	for i, p := range srcPeriods {
+		period, err := mapPeriod(i, p)
 		if err != nil {
 			return model.WeatherForecastRun{}, time.Time{}, err
 		}