package processor

import (
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"

	"apskel-pos-be/internal/models"
)

// wib is a moment in the customer's time zone.
func wib(year int, month time.Month, day, hour, minute int) time.Time {
	return time.Date(year, month, day, hour, minute, 0, 0, walletDisplayLocation)
}

// expiryDay is the day a lot expires on, as the apps show it.
func expiryDay(t *testing.T, at *time.Time) string {
	t.Helper()
	require.NotNil(t, at)
	local := at.In(walletDisplayLocation)
	assert.Equal(t, "23:59:59", local.Format("15:04:05"), "a lot lasts to the end of its day")
	return local.Format("2006-01-02")
}

func fixedDate(dates ...string) models.LoyaltyExpirySettings {
	return models.LoyaltyExpirySettings{Enabled: true, Mode: "FIXED_DATE", FixedDates: dates, GraceMonths: 3}
}

func rolling(period int64, unit string, endOfMonth bool) models.LoyaltyExpirySettings {
	return models.LoyaltyExpirySettings{Enabled: true, Mode: "ROLLING", Period: period, Unit: unit, EndOfMonth: endOfMonth}
}

func TestComputeExpiry_OffNeverExpires(t *testing.T) {
	s := fixedDate("12-31")
	s.Enabled = false
	assert.Nil(t, ComputeExpiry(s, wib(2026, 5, 1, 10, 0)))
}

func TestComputeExpiry_FixedDateWithGrace(t *testing.T) {
	yearly := fixedDate("12-31")
	for received, want := range map[time.Time]string{
		wib(2026, 1, 15, 9, 0):  "2026-12-31",
		wib(2026, 9, 30, 23, 0): "2026-12-31", // 30 Dec + nothing: still this year
		wib(2026, 10, 1, 0, 30): "2027-12-31", // within 3 months of 31 Dec: next year
		wib(2026, 12, 31, 8, 0): "2027-12-31",
	} {
		assert.Equal(t, want, expiryDay(t, ComputeExpiry(yearly, received)), received.String())
	}

	twice := fixedDate("12-31", "06-30")
	assert.Equal(t, "2026-06-30", expiryDay(t, ComputeExpiry(twice, wib(2026, 3, 1, 12, 0))))
	assert.Equal(t, "2026-12-31", expiryDay(t, ComputeExpiry(twice, wib(2026, 4, 1, 12, 0))))
	assert.Equal(t, "2027-06-30", expiryDay(t, ComputeExpiry(twice, wib(2026, 10, 1, 12, 0))))

	noGrace := fixedDate("12-31")
	noGrace.GraceMonths = 0
	assert.Equal(t, "2026-12-31", expiryDay(t, ComputeExpiry(noGrace, wib(2026, 12, 31, 22, 0))))
}

// The day received is the customer's day: 20:00 UTC on 31 Mar is already 1 Apr in WIB.
func TestComputeExpiry_UsesTheCustomersDay(t *testing.T) {
	received := time.Date(2026, 3, 31, 20, 0, 0, 0, time.UTC)
	assert.Equal(t, "2026-04-11", expiryDay(t, ComputeExpiry(rolling(10, "DAY", false), received)))
}

func TestComputeExpiry_Rolling(t *testing.T) {
	assert.Equal(t, "2027-03-14", expiryDay(t, ComputeExpiry(rolling(12, "MONTH", false), wib(2026, 3, 14, 10, 0))))
	assert.Equal(t, "2027-03-31", expiryDay(t, ComputeExpiry(rolling(12, "MONTH", true), wib(2026, 3, 14, 10, 0))))
	assert.Equal(t, "2026-03-24", expiryDay(t, ComputeExpiry(rolling(10, "DAY", false), wib(2026, 3, 14, 10, 0))))
	// A month that is shorter keeps to its last day.
	assert.Equal(t, "2026-02-28", expiryDay(t, ComputeExpiry(rolling(1, "MONTH", false), wib(2026, 1, 31, 10, 0))))
}

func TestActivationExpiry(t *testing.T) {
	// FIXED_DATE: the second fixed date after activation, so nobody loses a balance
	// weeks after the rule is announced.
	assert.Equal(t, "2027-12-31", expiryDay(t, ActivationExpiry(fixedDate("12-31"), wib(2026, 11, 20, 10, 0))))
	assert.Equal(t, "2027-12-31", expiryDay(t, ActivationExpiry(fixedDate("12-31"), wib(2026, 12, 31, 10, 0))))
	assert.Equal(t, "2027-06-30", expiryDay(t, ActivationExpiry(fixedDate("06-30", "12-31"), wib(2026, 11, 20, 10, 0))))
	// ROLLING: a full period from activation.
	assert.Equal(t, "2027-11-20", expiryDay(t, ActivationExpiry(rolling(12, "MONTH", false), wib(2026, 11, 20, 10, 0))))
}

func TestRefundExpiry(t *testing.T) {
	now := wib(2026, 6, 1, 10, 0)
	later := wib(2026, 12, 31, 23, 59)
	soon := wib(2026, 6, 3, 23, 59)
	past := wib(2026, 5, 1, 23, 59)

	assert.Nil(t, RefundExpiry(nil, now))
	assert.Equal(t, &later, RefundExpiry(&later, now))
	assert.Equal(t, "2026-06-08", expiryDay(t, RefundExpiry(&soon, now)))
	assert.Equal(t, "2026-06-08", expiryDay(t, RefundExpiry(&past, now)))
}

func TestEarlierExpiry(t *testing.T) {
	a, b := wib(2026, 1, 1, 0, 0), wib(2026, 2, 1, 0, 0)
	assert.Equal(t, &a, EarlierExpiry(&a, &b))
	assert.Equal(t, &a, EarlierExpiry(&b, &a))
	assert.Equal(t, &a, EarlierExpiry(nil, &a))
	assert.Equal(t, &a, EarlierExpiry(&a, nil))
	assert.Nil(t, EarlierExpiry(nil, nil))
}

func TestNormalizeDaysOfYear(t *testing.T) {
	days, err := normalizeDaysOfYear([]string{" 12-31", "06-30", "12-31", ""})
	require.NoError(t, err)
	assert.Equal(t, []string{"06-30", "12-31"}, days)
	for _, bad := range [][]string{{}, {"13-01"}, {"12-32"}, {"1-31"}, {"02-29"}, {"31-12"}} {
		_, err := normalizeDaysOfYear(bad)
		assert.Error(t, err, bad)
	}
}