Initial commit

internal/daterange/daterange_test.go

@@ -0,0 +1,36 @@
+package daterange
+
+import (
+	"testing"
+	"time"
+)
+
+func intPointer(value int) *int { return &value }
+
+func TestCalendarWindow(t *testing.T) {
+	tests := []struct {
+		name               string
+		now                time.Time
+		from               int
+		fromDay            *int
+		to                 int
+		toDay              *int
+		wantStart, wantEnd string
+	}{
+		{"ordinary", time.Date(2026, 6, 1, 0, 0, 0, 0, time.UTC), 2, nil, 3, nil, "2026-02-01", "2026-03-31"},
+		{"wrap before end", time.Date(2026, 1, 10, 0, 0, 0, 0, time.UTC), 11, nil, 2, nil, "2025-11-01", "2026-02-28"},
+		{"wrap before start", time.Date(2026, 9, 1, 0, 0, 0, 0, time.UTC), 11, nil, 2, nil, "2026-11-01", "2027-02-28"},
+		{"clamps invalid month day", time.Date(2026, 1, 1, 0, 0, 0, 0, time.UTC), 2, intPointer(31), 2, intPointer(31), "2026-02-28", "2026-02-28"},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			start, end := CalendarWindow(test.now, test.from, test.fromDay, test.to, test.toDay)
+			if got := start.Format("2006-01-02"); got != test.wantStart {
+				t.Errorf("start=%s", got)
+			}
+			if got := end.Format("2006-01-02"); got != test.wantEnd {
+				t.Errorf("end=%s", got)
+			}
+		})
+	}
+}