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)
			}
		})
	}
}