Correct daypart identity and display handling

internal/briefing/derived_daypart_summaries_module.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 	"sort"
 	"strings"
-	"unicode"
 
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/forecast"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/module"
@@ -80,6 +79,9 @@ func buildDerivedDaypartSummariesModule(ctx ModuleContext, _ any) (*module.Outpu
 	prefixDates := multipleSummaryDates(ctx.Derived.DailySummaries)
 	for _, daypart := range ctx.Derived.DaypartSummaries {
 		key := daypartKey(daypart, prefixDates)
+		if existing, exists := value[key]; exists {
+			return nil, fmt.Errorf("daypart summary key %q collides with display name %q", key, existing.DisplayName)
+		}
 		value[key] = derivedDaypartSummaryValue(daypart, ctx.Timezone)
 	}
 	return &module.Output{ID: module.DerivedDaypartSummaries, StanzaName: "derived_daypart_summaries", Value: value}, nil
@@ -135,7 +137,7 @@ func derivedDaypartSummaryValue(daypart forecast.DaypartSummary, timezone string
 	temperature := daypartTemperatureDisplay(daypart)
 	value := DerivedDaypartSummaryModule{
 		Date:                     localDateLabel(daypart.Period.Start, timezone),
-		DisplayName:              titleWord(strings.TrimSpace(daypart.Name)),
+		DisplayName:              capitalizeFirst(strings.TrimSpace(daypart.Name)),
 		PeriodBegins:             friendlyPeriodBeginsLabel(daypart.Period, timezone),
 		PeriodEnds:               friendlyPeriodEndsLabel(daypart.Period, timezone),
 		TempRangeF:               rangeLabel(daypart.Temperature),
@@ -148,7 +150,7 @@ func derivedDaypartSummaryValue(daypart forecast.DaypartSummary, timezone string
 		ApparentTempRangeF:       daypartApparentRangeLabel(daypart.ApparentTemperature),
 		DominantCondition:        daypart.DominantCondition,
 		DominantConditionLower:   strings.ToLower(daypart.DominantCondition),
-		DominantConditionDisplay: sentenceCase(daypart.DominantCondition),
+		DominantConditionDisplay: capitalizeFirst(strings.TrimSpace(daypart.DominantCondition)),
 		NotableConditions:        append([]string(nil), daypart.NotableConditions...),
 		Snow:                     daypart.Indicators.Snow,
 		Ice:                      daypart.Indicators.Ice,
@@ -381,16 +383,6 @@ func temperatureBandQualifier(remainder int) string {
 	}
 }
 
-func sentenceCase(value string) string {
-	trimmed := strings.TrimSpace(value)
-	if trimmed == "" {
-		return ""
-	}
-	runes := []rune(trimmed)
-	runes[0] = unicode.ToUpper(runes[0])
-	return string(runes)
-}
-
 func multipleSummaryDates(summaries []forecast.DailySummary) bool {
 	seen := map[string]struct{}{}
 	for _, summary := range summaries {