db.go

package money

import (
	"database/sql/driver"
	"fmt"
	"strings"

	"github.com/shopspring/decimal"
	"github.com/spf13/cast"
)

var (
	// DBMoneyValueSeparator is used to join together the Amount and Currency components of money.Money instances
	// allowing them to be stored as strings (via the driver.Valuer interface) and unmarshalled as strings (via
	// the sql.Scanner interface); set this value to use a different separator.
	DBMoneyValueSeparator = DefaultDBMoneyValueSeparator
)

const (
	// DefaultDBMoneyValueSeparator is the default value for DBMoneyValueSeparator; can be used to reset the
	// active separator value
	DefaultDBMoneyValueSeparator = "|"
)

// Value implements driver.Valuer to serialise a Money instance into a delimited string using the DBMoneyValueSeparator
// for example: "amount|currency_code"
func (m *Money) Value() (driver.Value, error) {
	code := ""
	if m.currency != nil {
		code = m.currency.Code
	}

	fraction := int32(2)
	if m.currency != nil {
		fraction = m.currency.Fraction
	}

	return fmt.Sprintf("%."+cast.ToString(fraction)+"f%s%s", m.Amount(), DBMoneyValueSeparator, code), nil
}

// Scan implements sql.Scanner to deserialize a Money instance from a DBMoneyValueSeparator-separated string
// for example: "amount|currency_code"
func (m *Money) Scan(src interface{}) error {
	var amount Amount
	currency := &Currency{}

	// let's support string and int64
	switch src := src.(type) {
	case string:
		parts := strings.Split(src, DBMoneyValueSeparator)
		if len(parts) != 2 || parts[0] == "" {
			return fmt.Errorf("%#v is not valid to scan into Money; update your query to return a money.DBMoneyValueSeparator-separated pair of \"amount%scurrency_code\"", src, DBMoneyValueSeparator)
		}

		_amount := cast.ToFloat64(parts[0])
		amount = decimal.NewFromFloat(_amount)

		if amount.IsZero() && parts[1] == "" {
			*m = Money{
				amount: amount,
			}
			return nil
		}
		if parts[1] == "" {
			return fmt.Errorf("%#v is not valid to scan into Money; update your query to return a money.DBMoneyValueSeparator-separated pair of \"amount%scurrency_code\"", src, DBMoneyValueSeparator)
		}
		if err := currency.Scan(parts[1]); err != nil {
			return fmt.Errorf("scanning %#v into a Currency: %v", parts[1], err)
		}
	default:
		return fmt.Errorf("don't know how to scan %T into Money; update your query to return a money.DBMoneyValueSeparator-separated pair of \"amount%scurrency_code\"", src, DBMoneyValueSeparator)
	}

	// allocate new Money with the scanned amount and currency
	*m = Money{
		amount:   amount,
		currency: currency,
	}

	return nil
}

// Value implements driver.Valuer to serialize a Currency code into a string for saving to a database
func (c Currency) Value() (driver.Value, error) {
	return c.Code, nil
}

// Scan implements sql.Scanner to deserialize a Currency from a string value read from a database
func (c *Currency) Scan(src interface{}) error {
	var val *Currency
	// let's support string only
	switch src := src.(type) {
	case string:
		val = GetCurrency(src)
	default:
		return fmt.Errorf("%T is not a supported type for a Currency (store the Currency.Code value as a string only)", src)
	}

	if val == nil {
		return fmt.Errorf("GetCurrency(%#v) returned nil", src)
	}

	// copy the value
	*c = *val

	return nil
}