internal/processor/earning_calculator.go

@@ -0,0 +1,85 @@
+package processor
+
+import (
+	"math"
+
+	"apskel-pos-be/internal/entities"
+	"apskel-pos-be/internal/models"
+)
+
+// EarningLine is what an order earns in one currency, and the settings that produced
+// it. The settings are kept so the ledger row can freeze them: a later change of
+// setting must not change what an earning meant, and a reversal is computed with the
+// same numbers (docs/prd-point-coin.md F3).
+type EarningLine struct {
+	Amount   int64
+	Settings models.LoyaltyEarnSettings
+	// True when max_per_order cut the amount down.
+	Capped bool
+}
+
+// EarningResult is what an order earns.
+type EarningResult struct {
+	// subtotal − discount − the part paid with EnakPoint, in rupiah, never negative.
+	// Tax and anything else added on top of the subtotal are not part of it (Q1).
+	Basis float64
+	Point EarningLine
+	Coin  EarningLine
+}
+
+// Metadata is the snapshot stored on the currency's EARN ledger row.
+func (r EarningResult) Metadata(line EarningLine) entities.Metadata {
+	m := entities.Metadata{
+		"basis":            r.Basis,
+		"earn_per_amount":  line.Settings.EarnPerAmount,
+		"earn_value":       line.Settings.EarnValue,
+		"min_order_amount": line.Settings.MinOrderAmount,
+		"capped":           line.Capped,
+	}
+	if line.Settings.MaxPerOrder != nil {
+		m["max_per_order"] = *line.Settings.MaxPerOrder
+	}
+	return m
+}
+
+// CalculateEarning applies the earning formula of docs/prd-point-coin.md F1:
+//
+//	basis  = subtotal − discount_amount − paid with EnakPoint
+//	amount = 0                                  if basis < min_order_amount
+//	amount = floor(basis / earn_per_amount) × earn_value
+//	amount = min(amount, max_per_order)         if max_per_order is set
+//
+// The part paid with EnakPoint earns nothing (Q10). Money is handled in whole cents so
+// floor never lands one short on a value like 87500.00 that float64 cannot hold
+// exactly. It has no side effects.
+func CalculateEarning(order *entities.Order, pointPaidAmount float64, settings models.OutletLoyaltySettings) EarningResult {
+	basisCents := toCents(order.Subtotal) - toCents(order.DiscountAmount) - toCents(pointPaidAmount)
+	if basisCents < 0 {
+		basisCents = 0
+	}
+	return EarningResult{
+		Basis: float64(basisCents) / 100,
+		Point: earnLine(basisCents, settings.Point),
+		Coin:  earnLine(basisCents, settings.Coin),
+	}
+}
+
+func earnLine(basisCents int64, s models.LoyaltyEarnSettings) EarningLine {
+	line := EarningLine{Settings: s}
+	if !s.Enabled || s.EarnPerAmount <= 0 || s.EarnValue <= 0 {
+		return line
+	}
+	if basisCents < s.MinOrderAmount*100 {
+		return line
+	}
+	line.Amount = basisCents / (s.EarnPerAmount * 100) * s.EarnValue
+	if s.MaxPerOrder != nil && line.Amount > *s.MaxPerOrder {
+		line.Amount = *s.MaxPerOrder
+		line.Capped = true
+	}
+	return line
+}
+
+func toCents(rupiah float64) int64 {
+	return int64(math.Round(rupiah * 100))
+}

internal/processor/earning_calculator_test.go

@@ -0,0 +1,121 @@
+package processor
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"apskel-pos-be/internal/entities"
+	"apskel-pos-be/internal/models"
+)
+
+// 1 EnakPoint per Rp 100 and 1 EnakCoin per Rp 25.000, as in the F1 example.
+func prdEarningSettings() models.OutletLoyaltySettings {
+	return models.OutletLoyaltySettings{
+		Point: models.LoyaltyEarnSettings{Enabled: true, EarnPerAmount: 100, EarnValue: 1},
+		Coin:  models.LoyaltyEarnSettings{Enabled: true, EarnPerAmount: 25000, EarnValue: 1},
+	}
+}
+
+func TestCalculateEarning_PRDExample(t *testing.T) {
+	// Subtotal after discount Rp 87.500, paid in full in cash.
+	order := &entities.Order{Subtotal: 97500, DiscountAmount: 10000, TaxAmount: 9625, TotalAmount: 97125}
+
+	got := CalculateEarning(order, 0, prdEarningSettings())
+	assert.Equal(t, 87500.0, got.Basis)
+	assert.Equal(t, int64(875), got.Point.Amount)
+	assert.Equal(t, int64(3), got.Coin.Amount)
+
+	// Rp 20.000 of it paid with EnakPoint earns nothing.
+	got = CalculateEarning(order, 20000, prdEarningSettings())
+	assert.Equal(t, 67500.0, got.Basis)
+	assert.Equal(t, int64(675), got.Point.Amount)
+	assert.Equal(t, int64(2), got.Coin.Amount)
+}
+
+func TestCalculateEarning_TaxIsNotPartOfTheBasis(t *testing.T) {
+	withoutTax := &entities.Order{Subtotal: 50000}
+	withTax := &entities.Order{Subtotal: 50000, TaxAmount: 5500, TotalAmount: 55500}
+	assert.Equal(t, CalculateEarning(withoutTax, 0, prdEarningSettings()), CalculateEarning(withTax, 0, prdEarningSettings()))
+	assert.Equal(t, int64(500), CalculateEarning(withTax, 0, prdEarningSettings()).Point.Amount)
+}
+
+func TestCalculateEarning_BelowMinimum(t *testing.T) {
+	s := prdEarningSettings()
+	s.Point.MinOrderAmount = 50000
+
+	assert.Equal(t, int64(0), CalculateEarning(&entities.Order{Subtotal: 49999}, 0, s).Point.Amount)
+	assert.Equal(t, int64(500), CalculateEarning(&entities.Order{Subtotal: 50000}, 0, s).Point.Amount, "the minimum itself earns")
+	// The minimum applies to the basis, after discount and EnakPoint.
+	assert.Equal(t, int64(0), CalculateEarning(&entities.Order{Subtotal: 60000}, 15000, s).Point.Amount)
+	// Coin has its own minimum.
+	assert.Equal(t, int64(1), CalculateEarning(&entities.Order{Subtotal: 49999}, 0, s).Coin.Amount)
+}
+
+func TestCalculateEarning_MaxPerOrder(t *testing.T) {
+	s := prdEarningSettings()
+	max := int64(300)
+	s.Point.MaxPerOrder = &max
+
+	got := CalculateEarning(&entities.Order{Subtotal: 87500}, 0, s)
+	assert.Equal(t, int64(300), got.Point.Amount)
+	assert.True(t, got.Point.Capped)
+	assert.Equal(t, int64(300), got.Metadata(got.Point)["max_per_order"])
+
+	got = CalculateEarning(&entities.Order{Subtotal: 20000}, 0, s)
+	assert.Equal(t, int64(200), got.Point.Amount)
+	assert.False(t, got.Point.Capped)
+
+	zero := int64(0)
+	s.Point.MaxPerOrder = &zero
+	assert.Equal(t, int64(0), CalculateEarning(&entities.Order{Subtotal: 87500}, 0, s).Point.Amount)
+}
+
+func TestCalculateEarning_DisabledEarnsNothing(t *testing.T) {
+	s := prdEarningSettings()
+	s.Point.Enabled = false
+	got := CalculateEarning(&entities.Order{Subtotal: 87500}, 0, s)
+	assert.Equal(t, int64(0), got.Point.Amount)
+	assert.Equal(t, int64(3), got.Coin.Amount, "each currency is switched on its own")
+
+	s.Coin.Enabled = false
+	got = CalculateEarning(&entities.Order{Subtotal: 87500}, 0, s)
+	assert.Equal(t, int64(0), got.Coin.Amount)
+	assert.Equal(t, 87500.0, got.Basis, "the basis is still reported")
+
+	// The defaults of an outlet that never set anything earn nothing.
+	var defaults models.OutletLoyaltySettings
+	loadLoyaltyFields(outletLoyaltyFields(&defaults), nil, "test")
+	got = CalculateEarning(&entities.Order{Subtotal: 87500}, 0, defaults)
+	assert.Equal(t, int64(0), got.Point.Amount)
+	assert.Equal(t, int64(0), got.Coin.Amount)
+}
+
+func TestCalculateEarning_EdgeCases(t *testing.T) {
+	s := prdEarningSettings()
+
+	// floor, not round.
+	assert.Equal(t, int64(875), CalculateEarning(&entities.Order{Subtotal: 87599.99}, 0, s).Point.Amount)
+	// Values float64 cannot hold exactly do not lose a point: computed in float64 this
+	// basis divides to 4956.999…, which a naive floor turns into 4956.
+	per250 := prdEarningSettings()
+	per250.Point.EarnPerAmount = 250
+	assert.Equal(t, int64(4957), CalculateEarning(&entities.Order{Subtotal: 1240155.48, DiscountAmount: 749.11}, 156.37, per250).Point.Amount)
+	// Paying more with EnakPoint than the basis leaves nothing, never a negative amount.
+	got := CalculateEarning(&entities.Order{Subtotal: 10000}, 15000, s)
+	assert.Equal(t, 0.0, got.Basis)
+	assert.Equal(t, int64(0), got.Point.Amount)
+	// earn_value multiplies.
+	s.Point.EarnValue = 5
+	assert.Equal(t, int64(4375), CalculateEarning(&entities.Order{Subtotal: 87500}, 0, s).Point.Amount)
+	// A zero earn_value earns nothing even when enabled.
+	s.Point.EarnValue = 0
+	assert.Equal(t, int64(0), CalculateEarning(&entities.Order{Subtotal: 87500}, 0, s).Point.Amount)
+}
+
+func TestCalculateEarning_MetadataSnapshot(t *testing.T) {
+	got := CalculateEarning(&entities.Order{Subtotal: 87500}, 0, prdEarningSettings())
+	assert.Equal(t, entities.Metadata{
+		"basis": 87500.0, "earn_per_amount": int64(100), "earn_value": int64(1), "min_order_amount": int64(0), "capped": false,
+	}, got.Metadata(got.Point))
+}