Fix discount logic

internal/server/api.go

@@ -28,43 +28,11 @@ func (s *Server) newPricingHandler() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		items := s.PriceCache.GetPrices()
 
-		// Pick the first yearly and monthly price that we find in the cache
-		// based on no particular order (since we expect to only have one of each)
-		var yearly, monthly *payment.Price
-		for _, price := range items {
-			price := price // GO WHY ARE YOU THIS WAY
-
-			if price.Annual && yearly == nil {
-				yearly = price
-			}
-			if !price.Annual && monthly == nil {
-				monthly = price
-			}
-			if monthly != nil && yearly != nil {
-				break
-			}
-		}
-
-		prices := &prices{}
-		if yearly != nil {
-			prices.Yearly.Price = yearly.Price
-			for _, discount := range yearly.CouponAmountsOff {
-				prices.Yearly.Discount = discount
-			}
-		}
-
-		if monthly != nil {
-			prices.Monthly.Price = monthly.Price
-			for _, discount := range monthly.CouponAmountsOff {
-				prices.Monthly.Discount = discount
-			}
-		}
-
 		w.Header().Set("Content-Type", "application/json")
 		w.Header().Set("Access-Control-Allow-Origin", "*")
 		w.Header().Set("Access-Control-Allow-Headers", "*")
 		w.Header().Set("Access-Control-Allow-Methods", "GET")
-		json.NewEncoder(w).Encode(prices)
+		json.NewEncoder(w).Encode(newPrices(items))
 	}
 }
 
@@ -73,7 +41,57 @@ type prices struct {
 	Monthly price `json:"monthly"`
 }
 
+func newPrices(items []*payment.Price) *prices {
+	// Pick the first yearly and monthly price that we find in the cache
+	// based on no particular order (since we expect to only have one of each)
+	var yearly, monthly *payment.Price
+	for _, price := range items {
+		price := price // GO WHY ARE YOU THIS WAY
+
+		if price.Annual && yearly == nil {
+			yearly = price
+		}
+		if !price.Annual && monthly == nil {
+			monthly = price
+		}
+		if monthly != nil && yearly != nil {
+			break
+		}
+	}
+
+	// Convert to our API response types
+	// When selecting discounts, pick the smallest i.e. most expensive.
+	prices := &prices{}
+	if yearly != nil {
+		prices.Yearly.Price = yearly.Price
+
+		var discount float64
+		for _, c := range yearly.CouponAmountsOff {
+			fd := float64(c) / 100
+			if fd < discount || discount == 0 {
+				discount = float64(c) / 100
+			}
+		}
+		prices.Yearly.Discounted = prices.Yearly.Price - discount
+	}
+
+	if monthly != nil {
+		prices.Monthly.Price = monthly.Price
+
+		var discount float64
+		for _, c := range monthly.CouponAmountsOff {
+			fd := float64(c) / 100
+			if fd < discount || discount == 0 {
+				discount = float64(c) / 100
+			}
+		}
+		prices.Monthly.Discounted = prices.Monthly.Price - discount
+	}
+
+	return prices
+}
+
 type price struct {
-	Price    float64 `json:"price"`
-	Discount int64   `json:"discount"`
+	Price      float64 `json:"price"`
+	Discounted float64 `json:"discount"`
 }

internal/server/api_test.go

@@ -0,0 +1,45 @@
+package server
+
+import (
+	"testing"
+
+	"github.com/TheLab-ms/profile/internal/payment"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewPrices(t *testing.T) {
+	items := []*payment.Price{
+		{
+			Price:            123,
+			CouponAmountsOff: map[string]int64{"foo": 1000, "bar": 300},
+		},
+		{
+			Annual:           true,
+			Price:            234,
+			CouponAmountsOff: map[string]int64{"foo": 1100, "bar": 350},
+		},
+		{
+			Annual: true,
+			Price:  1230, // this won't be picked because it isn't first
+		},
+		{
+			Price: 2340, // this won't be picked because it isn't first
+		},
+	}
+
+	actual := newPrices(items)
+	exp := &prices{
+		Yearly: price{
+			Price:      234,
+			Discounted: 230.5,
+		},
+		Monthly: price{
+			Price:      123,
+			Discounted: 120,
+		},
+	}
+	assert.Equal(t, exp, actual)
+
+	// also doesn't panic when empty
+	newPrices(nil)
+}