trying to fix price

models/data.go

@@ -5,7 +5,7 @@ import "time"
 type Cake struct {
 	Name   string
 	ID     int
-	Price  int // increments of 0.01
+	Price  Price // increments of 0.01
 	Amount int
 }
 
@@ -18,18 +18,22 @@ type Order struct {
 	Date     time.Time
 	Accepted time.Time
 	Status   string
-	Paid     int // increments of 0.01
+	Paid     Price // increments of 0.01
 	Cakes    []Cake
 }
 
-func (o *Order) Total() int {
-	out := o.Paid * (-1)
+func (o *Order) Subtotal() Price {
+	var out Price
 	for _, e := range o.Cakes {
-		out += e.Price * e.Amount
+		out += e.Price * Price(e.Amount)
 	}
 	return out
+
+}
+func (o *Order) Total() Price {
+	return o.Subtotal() - o.Paid
 }
 
-func (c *Cake) Total() int {
-	return c.Amount * c.Price
+func (c *Cake) Total() Price {
+	return Price(c.Amount) * c.Price
 }

models/price.go

@@ -0,0 +1,33 @@
+package models
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+type Price int
+
+func (in Price) String() string {
+	if in%100 == 0 {
+		return strconv.Itoa(int(in) / 100)
+	} else {
+		price := strconv.Itoa(int(in))
+		i := len(price) - 2
+		price = price[:i] + "." + price[i:]
+		return price
+	}
+}
+
+func ParsePrice(in string) (Price, error) {
+	if !strings.Contains(in, ".") {
+		price, err := strconv.Atoi(in)
+		return Price(price) * 100, err
+	}
+	before, after, _ := strings.Cut(in, ".")
+	if len(after) != 2 {
+		return 0, fmt.Errorf("Wrong format, requires exactly 2 decimal places after '.'")
+	}
+	price, err := strconv.Atoi(before + after)
+	return Price(price), err
+}

models/price_test.go

@@ -0,0 +1,55 @@
+package models
+
+import "testing"
+
+func TestFormatPrice(t *testing.T) {
+	var a Price
+	var s string
+	a = 12345678900
+	s = a.String()
+	if s != "123456789" {
+		t.Fatal(a, s)
+	}
+	a = 123456789
+	s = a.String()
+	if s != "1234567.89" {
+		t.Fatal(a, s)
+	}
+}
+
+func TestParsePrice(t *testing.T) {
+	var p Price
+	var s string
+	var err error
+	s = "199"
+	p, err = ParsePrice(s)
+	if err != nil || p != 19900 {
+		t.Fatal(s, p)
+	}
+	s = "1.99"
+	p, err = ParsePrice(s)
+	if err != nil || p != 199 {
+		t.Fatal(s, p)
+	}
+	s = "1123"
+	p, err = ParsePrice(s)
+	if err != nil || p != 112300 {
+		t.Fatal(s, p)
+	}
+	s = "1123.123"
+	_, err = ParsePrice(s)
+	if err == nil {
+		t.Fatal(s, "should error")
+	}
+	s = "1123.3"
+	_, err = ParsePrice(s)
+	if err == nil {
+		t.Fatal(s, "should error")
+	}
+
+	s = "1123,33"
+	_, err = ParsePrice(s)
+	if err == nil {
+		t.Fatal(s, "should error")
+	}
+}