package fees

import "testing"

func TestCalculateFee(t *testing.T) {
	t.Parallel()

	// mustRate returns the configured rate for a month that must be in the map.
	// It panics immediately if the month is absent — so if a rate entry is ever
	// removed, the test fails loudly rather than silently comparing against
	// Go's zero value.
	mustRate := func(month string) int {
		r, ok := AdultFeeMonthlyRate[month]
		if !ok {
			panic("test month not in AdultFeeMonthlyRate: " + month)
		}
		return r
	}

	tests := []struct {
		name  string
		count int
		month string
		want  int
	}{
		// Zero attendance always returns 0.
		{"zero short-circuits", 0, "2026-05", 0},
		{"zero empty month", 0, "", 0},
		// Single practice returns AdultFeeSingle regardless of month.
		{"single practice", 1, "2026-05", AdultFeeSingle},
		{"single ignores monthKey", 1, "unknown", AdultFeeSingle},
		// Two+ practices for a configured month: must use the map value, not the default.
		// Expected values are read from AdultFeeMonthlyRate so this test stays correct
		// when rates are updated — the assertion verifies dispatch logic, not rate values.
		{"two practices configured month", 2, "2026-05", mustRate("2026-05")},
		{"two practices reduced march", 2, "2026-03", mustRate("2026-03")},
		{"two practices early season", 2, "2025-09", mustRate("2025-09")},
		{"high count same as two", 5, "2026-05", mustRate("2026-05")},
		// Two+ practices for an unknown/future month: must fall back to AdultFeeDefault.
		{"unknown future month falls back", 2, "2027-01", AdultFeeDefault},
		{"empty month falls back", 2, "", AdultFeeDefault},
	}

	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()
			got := CalculateFee(tc.count, tc.month)
			if got != tc.want {
				t.Errorf("CalculateFee(%d, %q) = %d, want %d", tc.count, tc.month, got, tc.want)
			}
		})
	}
}