Extract package

postgres/numeric/numeric.go

@@ -0,0 +1,193 @@
+package numeric
+
+import (
+	"fmt"
+	"math/big"
+	"strings"
+	"unicode/utf8"
+
+	"github.com/jackc/pgtype"
+)
+
+type Numeric struct {
+	pgtype.Numeric
+}
+
+func Zero() Numeric {
+	return Numeric{pgtype.Numeric{Exp: 0, Int: big.NewInt(0), Status: pgtype.Present, NaN: false}}
+}
+
+func (n Numeric) GetFloat64() float64 {
+	if n.Status != pgtype.Present {
+		return 0
+	}
+	var balance float64
+	err := n.AssignTo(&balance)
+	if err != nil {
+		panic(err)
+	}
+	return balance
+}
+
+func (n Numeric) IsPositive() bool {
+	if n.Status != pgtype.Present {
+		return true
+	}
+	float := n.GetFloat64()
+	return float >= 0
+}
+
+func (n Numeric) IsZero() bool {
+	if n.Status != pgtype.Present {
+		return true
+	}
+	float := n.GetFloat64()
+	return float == 0
+}
+
+func (n Numeric) MatchExp(exp int32) Numeric {
+	diffExp := n.Exp - exp
+	factor := big.NewInt(0).Exp(big.NewInt(10), big.NewInt(int64(diffExp)), nil) //nolint:gomnd
+	return Numeric{pgtype.Numeric{
+		Exp:    exp,
+		Int:    big.NewInt(0).Mul(n.Int, factor),
+		Status: n.Status,
+		NaN:    n.NaN,
+	}}
+}
+
+func (n Numeric) Sub(other Numeric) Numeric {
+	left := n
+	right := other
+	if n.Exp < other.Exp {
+		right = other.MatchExp(n.Exp)
+	} else if n.Exp > other.Exp {
+		left = n.MatchExp(other.Exp)
+	}
+
+	if left.Exp == right.Exp {
+		return Numeric{pgtype.Numeric{
+			Exp: left.Exp,
+			Int: big.NewInt(0).Sub(left.Int, right.Int),
+		}}
+	}
+
+	panic("Cannot subtract with different exponents")
+}
+
+func (n Numeric) Add(other Numeric) Numeric {
+	left := n
+	right := other
+	if n.Exp < other.Exp {
+		right = other.MatchExp(n.Exp)
+	} else if n.Exp > other.Exp {
+		left = n.MatchExp(other.Exp)
+	}
+
+	if left.Exp == right.Exp {
+		return Numeric{pgtype.Numeric{
+			Exp: left.Exp,
+			Int: big.NewInt(0).Add(left.Int, right.Int),
+		}}
+	}
+
+	panic("Cannot add with different exponents")
+}
+
+func (n Numeric) String() string {
+	if n.Int == nil || n.Int.Int64() == 0 {
+		return "0"
+	}
+
+	s := fmt.Sprintf("%d", n.Int)
+	bytes := []byte(s)
+
+	exp := n.Exp
+	for exp > 0 {
+		bytes = append(bytes, byte('0'))
+		exp--
+	}
+
+	if exp == 0 {
+		return string(bytes)
+	}
+
+	length := int32(len(bytes))
+	var bytesWithSeparator []byte
+
+	exp = -exp
+	for length <= exp {
+		bytes = append(bytes, byte('0'))
+		length++
+	}
+
+	split := length - exp
+	bytesWithSeparator = append(bytesWithSeparator, bytes[:split]...)
+	if split == 1 && n.Int.Int64() < 0 {
+		bytesWithSeparator = append(bytesWithSeparator, byte('0'))
+	}
+	bytesWithSeparator = append(bytesWithSeparator, byte('.'))
+	bytesWithSeparator = append(bytesWithSeparator, bytes[split:]...)
+	return string(bytesWithSeparator)
+}
+
+func (n Numeric) MarshalJSON() ([]byte, error) {
+	if n.Int == nil || n.Int.Int64() == 0 {
+		return []byte("0"), nil
+	}
+
+	s := fmt.Sprintf("%d", n.Int)
+	bytes := []byte(s)
+
+	exp := n.Exp
+	for exp > 0 {
+		bytes = append(bytes, byte('0'))
+		exp--
+	}
+
+	if exp == 0 {
+		return bytes, nil
+	}
+
+	length := int32(len(bytes))
+	var bytesWithSeparator []byte
+
+	exp = -exp
+	for length <= exp {
+		bytes = append(bytes, byte('0'))
+		length++
+	}
+
+	split := length - exp
+	bytesWithSeparator = append(bytesWithSeparator, bytes[:split]...)
+	if split == 1 && n.Int.Int64() < 0 {
+		bytesWithSeparator = append(bytesWithSeparator, byte('0'))
+	}
+	bytesWithSeparator = append(bytesWithSeparator, byte('.'))
+	bytesWithSeparator = append(bytesWithSeparator, bytes[split:]...)
+	return bytesWithSeparator, nil
+}
+
+func Parse(text string) (Numeric, error) {
+	// Remove trailing currency
+	text = trimLastChar(text)
+
+	// Unify decimal separator
+	text = strings.Replace(text, ",", ".", 1)
+
+	num := Numeric{}
+	err := num.Set(text)
+	if err != nil {
+		return num, fmt.Errorf("parse numeric %s: %w", text, err)
+	}
+
+	return num, nil
+}
+
+func trimLastChar(s string) string {
+	r, size := utf8.DecodeLastRuneInString(s)
+	if r == utf8.RuneError && (size == 0 || size == 1) {
+		size = 0
+	}
+	return s[:len(s)-size]
+}