api for initial widgets

money/currency.go

@@ -0,0 +1,8 @@
+package money
+
+type Currency string
+
+const (
+	USD Currency = "USD"
+	CAD          = "CAD"
+)

money/money.go

@@ -0,0 +1,31 @@
+package money
+
+type Money struct {
+	Currency Currency `json:"currency" bson:"currency"`
+	Whole    int      `json:"whole" bson:"whole"`
+	Decimal  int      `json:"decimal" bson:"decimal"`
+}
+
+// add x to y
+func Add(x, y Money) Money {
+	x.Decimal += y.Decimal
+	if x.Decimal >= 100 {
+		x.Whole++
+		x.Decimal -= 100
+	}
+	x.Whole += y.Whole
+
+	return x
+}
+
+// subtract x from y
+func Subtract(x, y Money) Money {
+	x.Decimal = y.Decimal - x.Decimal
+	if x.Decimal < 0 {
+		x.Whole++
+		x.Decimal += 100
+	}
+	x.Whole = y.Whole - x.Whole
+
+	return x
+}