From ccc7cc2931b8f0b3df41e1f5c1e7322d708b6623 Mon Sep 17 00:00:00 2001
From: Oleg Lomaka <oleg.lomaka@gmail.com>
Date: Tue, 4 Jan 2022 16:25:19 +0200
Subject: [PATCH] Assign Numeric to *big.Rat

---
 numeric.go      | 26 ++++++++++++++++++++++++++
 numeric_test.go | 13 +++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/numeric.go b/numeric.go
index a939625b..cd057749 100644
--- a/numeric.go
+++ b/numeric.go
@@ -369,6 +369,12 @@ func (src *Numeric) AssignTo(dst interface{}) error {
 				return fmt.Errorf("%d is greater than maximum value for %T", normalizedInt, *v)
 			}
 			*v = normalizedInt.Uint64()
+		case *big.Rat:
+			rat, err := src.toBigRat()
+			if err != nil {
+				return err
+			}
+			v.Set(rat)
 		default:
 			if nextDst, retry := GetAssignToDstType(dst); retry {
 				return src.AssignTo(nextDst)
@@ -406,6 +412,26 @@ func (dst *Numeric) toBigInt() (*big.Int, error) {
 	return num, nil
 }
 
+func (dst *Numeric) toBigRat() (*big.Rat, error) {
+	if dst.NaN {
+		return nil, fmt.Errorf("%v is not a number", dst)
+	} else if dst.InfinityModifier == Infinity {
+		return nil, fmt.Errorf("%v is infinity", dst)
+	} else if dst.InfinityModifier == NegativeInfinity {
+		return nil, fmt.Errorf("%v is -infinity", dst)
+	}
+
+	num := new(big.Rat).SetInt(dst.Int)
+	if dst.Exp > 0 {
+		mul := new(big.Int).Exp(big10, big.NewInt(int64(dst.Exp)), nil)
+		num.Mul(num, new(big.Rat).SetInt(mul))
+	} else if dst.Exp < 0 {
+		mul := new(big.Int).Exp(big10, big.NewInt(int64(-dst.Exp)), nil)
+		num.Quo(num, new(big.Rat).SetInt(mul))
+	}
+	return num, nil
+}
+
 func (src *Numeric) toFloat64() (float64, error) {
 	if src.NaN {
 		return math.NaN(), nil
diff --git a/numeric_test.go b/numeric_test.go
index 455c3ac3..83334a04 100644
--- a/numeric_test.go
+++ b/numeric_test.go
@@ -263,6 +263,7 @@ func TestNumericAssignTo(t *testing.T) {
 	var f64 float64
 	var pf32 *float32
 	var pf64 *float64
+	var br = new(big.Rat)
 
 	simpleTests := []struct {
 		src      *pgtype.Numeric
@@ -293,6 +294,9 @@ func TestNumericAssignTo(t *testing.T) {
 		{src: &pgtype.Numeric{Status: pgtype.Present, InfinityModifier: pgtype.Infinity}, dst: &f32, expected: float32(math.Inf(1))},
 		{src: &pgtype.Numeric{Status: pgtype.Present, InfinityModifier: pgtype.NegativeInfinity}, dst: &f64, expected: math.Inf(-1)},
 		{src: &pgtype.Numeric{Status: pgtype.Present, InfinityModifier: pgtype.NegativeInfinity}, dst: &f32, expected: float32(math.Inf(-1))},
+		{src: &pgtype.Numeric{Int: big.NewInt(-1023), Exp: -2, Status: pgtype.Present}, dst: br, expected: big.NewRat(-1023, 100)},
+		{src: &pgtype.Numeric{Int: big.NewInt(-1023), Exp: 2, Status: pgtype.Present}, dst: br, expected: big.NewRat(-102300, 1)},
+		{src: &pgtype.Numeric{Int: big.NewInt(23), Exp: 0, Status: pgtype.Present}, dst: br, expected: big.NewRat(23, 1)},
 	}
 
 	for i, tt := range simpleTests {
@@ -317,6 +321,11 @@ func TestNumericAssignTo(t *testing.T) {
 			} else if !nanExpected && dst != tt.expected {
 				t.Errorf("%d: expected %v to assign %v, but result was %v", i, tt.src, tt.expected, dst)
 			}
+		case big.Rat:
+			if (&dstTyped).Cmp(tt.expected.(*big.Rat)) != 0 {
+				t.Errorf("%d: expected %v to assign %v, but result was %v",
+					i, tt.src, tt.expected, dst)
+			}
 		default:
 			if dst != tt.expected {
 				t.Errorf("%d: expected %v to assign %v, but result was %v", i, tt.src, tt.expected, dst)
@@ -356,6 +365,10 @@ func TestNumericAssignTo(t *testing.T) {
 		{src: &pgtype.Numeric{Int: big.NewInt(-1), Status: pgtype.Present}, dst: &ui64},
 		{src: &pgtype.Numeric{Int: big.NewInt(-1), Status: pgtype.Present}, dst: &ui},
 		{src: &pgtype.Numeric{Int: big.NewInt(0), Status: pgtype.Null}, dst: &i32},
+		{src: &pgtype.Numeric{Int: big.NewInt(0), Status: pgtype.Null}, dst: br},
+		{src: &pgtype.Numeric{Int: big.NewInt(0), Status: pgtype.Present, NaN: true}, dst: br},
+		{src: &pgtype.Numeric{Int: big.NewInt(0), Status: pgtype.Present, InfinityModifier: pgtype.Infinity}, dst: br},
+		{src: &pgtype.Numeric{Int: big.NewInt(0), Status: pgtype.Present, InfinityModifier: pgtype.NegativeInfinity}, dst: br},
 	}
 
 	for i, tt := range errorTests {