service backend

api/pkg/decimal/money.go

@@ -0,0 +1,129 @@
+package decimal
+
+import (
+	"math/big"
+
+	"github.com/tech/sendico/pkg/merrors"
+)
+
+// Money represents a monetary amount with currency and precision handling
+type Money struct {
+	Amount   *big.Rat
+	Currency string
+	Scale    uint32 // decimal places for this currency
+}
+
+// NewMoney creates a new Money value from a decimal string
+func NewMoney(amount, currency string, scale uint32) (*Money, error) {
+	rat, err := RatFromString(amount)
+	if err != nil {
+		return nil, err
+	}
+	return &Money{
+		Amount:   rat,
+		Currency: currency,
+		Scale:    scale,
+	}, nil
+}
+
+// Add adds two money values (must have same currency)
+func (m *Money) Add(other *Money) (*Money, error) {
+	if m.Currency != other.Currency {
+		return nil, merrors.InvalidArgument("decimal: currency mismatch: " + m.Currency + " != " + other.Currency)
+	}
+	return &Money{
+		Amount:   AddRat(m.Amount, other.Amount),
+		Currency: m.Currency,
+		Scale:    m.Scale,
+	}, nil
+}
+
+// Sub subtracts two money values (must have same currency)
+func (m *Money) Sub(other *Money) (*Money, error) {
+	if m.Currency != other.Currency {
+		return nil, merrors.InvalidArgument("decimal: currency mismatch: " + m.Currency + " != " + other.Currency)
+	}
+	return &Money{
+		Amount:   SubRat(m.Amount, other.Amount),
+		Currency: m.Currency,
+		Scale:    m.Scale,
+	}, nil
+}
+
+// Mul multiplies money by a rational number (for fees, percentages, etc.)
+func (m *Money) Mul(factor *big.Rat) *Money {
+	return &Money{
+		Amount:   MulRat(m.Amount, factor),
+		Currency: m.Currency,
+		Scale:    m.Scale,
+	}
+}
+
+// Div divides money by a rational number
+func (m *Money) Div(divisor *big.Rat) (*Money, error) {
+	result, err := DivRat(m.Amount, divisor)
+	if err != nil {
+		return nil, err
+	}
+	return &Money{
+		Amount:   result,
+		Currency: m.Currency,
+		Scale:    m.Scale,
+	}, nil
+}
+
+// Negate returns the negative of this money value
+func (m *Money) Negate() *Money {
+	return &Money{
+		Amount:   NegRat(m.Amount),
+		Currency: m.Currency,
+		Scale:    m.Scale,
+	}
+}
+
+// Round rounds the money to its scale using the specified rounding mode
+func (m *Money) Round(mode RoundingMode) (*Money, error) {
+	rounded, err := RoundRatToScale(m.Amount, m.Scale, mode)
+	if err != nil {
+		return nil, err
+	}
+	return &Money{
+		Amount:   rounded,
+		Currency: m.Currency,
+		Scale:    m.Scale,
+	}, nil
+}
+
+// String returns the formatted money value
+func (m *Money) String() string {
+	return FormatRat(m.Amount, m.Scale) + " " + m.Currency
+}
+
+// StringAmount returns just the formatted amount
+func (m *Money) StringAmount() string {
+	return FormatRat(m.Amount, m.Scale)
+}
+
+// IsZero checks if the money amount is zero
+func (m *Money) IsZero() bool {
+	return IsZero(m.Amount)
+}
+
+// IsPositive checks if the money amount is positive
+func (m *Money) IsPositive() bool {
+	return IsPositive(m.Amount)
+}
+
+// IsNegative checks if the money amount is negative
+func (m *Money) IsNegative() bool {
+	return IsNegative(m.Amount)
+}
+
+// Cmp compares two money values (must have same currency)
+// Returns -1 if m < other, 0 if m == other, 1 if m > other
+func (m *Money) Cmp(other *Money) (int, error) {
+	if m.Currency != other.Currency {
+		return 0, merrors.InvalidArgument("decimal: currency mismatch: " + m.Currency + " != " + other.Currency)
+	}
+	return CmpRat(m.Amount, other.Amount), nil
+}