fix: anchor growth forecasts to real Tehran date

internal/insight/time.go

@@ -0,0 +1,49 @@
+package insight
+
+import "time"
+
+type Freshness string
+
+const (
+	FreshnessFresh   Freshness = "FRESH"
+	FreshnessLagging Freshness = "LAGGING"
+	FreshnessStale   Freshness = "STALE"
+)
+
+type TimeContext struct {
+	AsOfDate          string    `json:"asOfDate"`
+	DataThroughDate   string    `json:"dataThroughDate"`
+	ForecastStartDate string    `json:"forecastStartDate"`
+	Freshness         Freshness `json:"freshness"`
+	DataLagDays       int       `json:"dataLagDays"`
+}
+
+func BuildTimeContext(now, dataThrough time.Time) TimeContext {
+	location, err := time.LoadLocation("Asia/Tehran")
+	if err != nil {
+		location = time.FixedZone("Asia/Tehran", 3*60*60+30*60)
+	}
+	today := dateOnly(now.In(location), location)
+	through := dateOnly(dataThrough.In(location), location)
+	lag := max(0, int(today.Sub(through).Hours()/24))
+	return TimeContext{
+		AsOfDate: today.Format(time.DateOnly), DataThroughDate: through.Format(time.DateOnly),
+		ForecastStartDate: today.Format(time.DateOnly), Freshness: ClassifyFreshness(lag), DataLagDays: lag,
+	}
+}
+
+func ClassifyFreshness(lagDays int) Freshness {
+	switch {
+	case lagDays <= 1:
+		return FreshnessFresh
+	case lagDays <= 7:
+		return FreshnessLagging
+	default:
+		return FreshnessStale
+	}
+}
+
+func dateOnly(value time.Time, location *time.Location) time.Time {
+	year, month, day := value.In(location).Date()
+	return time.Date(year, month, day, 0, 0, 0, 0, location)
+}

internal/insight/time_test.go

@@ -0,0 +1,51 @@
+package insight
+
+import (
+	"testing"
+	"time"
+)
+
+func TestTimeContextUsesRealTehranTodayAndReportsDatasetLag(t *testing.T) {
+	t.Parallel()
+
+	now := time.Date(2026, time.August, 21, 8, 30, 0, 0, time.UTC)
+	dataThrough := time.Date(2026, time.June, 30, 0, 0, 0, 0, time.UTC)
+
+	got := BuildTimeContext(now, dataThrough)
+
+	if got.AsOfDate != "2026-08-21" {
+		t.Fatalf("AsOfDate = %q, want real Tehran date", got.AsOfDate)
+	}
+	if got.DataThroughDate != "2026-06-30" {
+		t.Fatalf("DataThroughDate = %q", got.DataThroughDate)
+	}
+	if got.ForecastStartDate != got.AsOfDate {
+		t.Fatalf("ForecastStartDate = %q, want %q", got.ForecastStartDate, got.AsOfDate)
+	}
+	if got.Freshness != FreshnessStale || got.DataLagDays != 52 {
+		t.Fatalf("freshness = %s, lag = %d", got.Freshness, got.DataLagDays)
+	}
+}
+
+func TestClassifyFreshnessUsesProductionBoundaries(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name string
+		lag  int
+		want Freshness
+	}{
+		{name: "same day", lag: 0, want: FreshnessFresh},
+		{name: "yesterday", lag: 1, want: FreshnessFresh},
+		{name: "two days", lag: 2, want: FreshnessLagging},
+		{name: "seven days", lag: 7, want: FreshnessLagging},
+		{name: "eight days", lag: 8, want: FreshnessStale},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := ClassifyFreshness(tt.lag); got != tt.want {
+				t.Fatalf("ClassifyFreshness(%d) = %s, want %s", tt.lag, got, tt.want)
+			}
+		})
+	}
+}