Properly register array and composite PostgreSQL types with pgtype

I have moved everything into a different file, even though it is related
to “db”, because it was starting to get a bit ugly.

Apparently i was doing too much work and had to read the code to
understand what i was supposed to do, because pgtypes’ documentation,
as all other projects from the same author, is almost non-existent.

go.mod

@@ -10,7 +10,6 @@ require (
 )
 
 require (
-	github.com/jackc/pgio v1.0.0
 	github.com/jackc/pgtype v1.12.0
 	golang.org/x/crypto v0.0.0-20220829220503-c86fa9a7ed90 // indirect
 )

pkg/db.go

@@ -4,8 +4,6 @@ import (
 	"context"
 	"log"
 
-	"github.com/jackc/pgio"
-	"github.com/jackc/pgtype"
 	"github.com/jackc/pgx/v4"
 	"github.com/jackc/pgx/v4/pgxpool"
 )
@@ -14,66 +12,6 @@ type Db struct {
 	*pgxpool.Pool
 }
 
-type newInvoiceProductArray []*invoiceProductForm
-
-type discountRate struct {
-	pgtype.Numeric
-}
-
-func (form *invoiceProductForm) EncodeBinary(ci *pgtype.ConnInfo, buf []byte) (newBuff []byte, err error) {
-	productId := &pgtype.Int4{}
-	if err = productId.Set(form.ProductId.Val); err != nil {
-		return
-	}
-	name := &pgtype.Text{String: form.Name.Val, Status: pgtype.Present}
-	description := &pgtype.Text{String: form.Description.Val, Status: pgtype.Present}
-	price := &pgtype.Text{String: form.Price.Val, Status: pgtype.Present}
-	quantity := &pgtype.Int4{}
-	if err = quantity.Set(form.Quantity.Val); err != nil {
-		return
-	}
-	discount := &discountRate{}
-	if err = discount.Set(form.Discount.Val); err != nil {
-		return
-	}
-	tax := &pgtype.Int4Array{}
-	if err = tax.Set(form.Tax.Selected); err != nil {
-		return
-	}
-	ct := pgtype.CompositeFields{productId, name, description, price, quantity, discount, tax}
-	return ct.EncodeBinary(ci, buf)
-}
-
-func (src newInvoiceProductArray) EncodeBinary(ci *pgtype.ConnInfo, buf []byte) ([]byte, error) {
-	arrayHeader := pgtype.ArrayHeader{
-		Dimensions: []pgtype.ArrayDimension{{Length: int32(len(src)), LowerBound: 1}},
-	}
-
-	/*typeName := "numerus.new_invoice_product"
-	if dt, ok := ci.DataTypeForName(typeName); ok {
-		arrayHeader.ElementOID = int32(dt.OID)
-	} else {
-		return nil, fmt.Errorf("unable to find oid for type name %v", typeName)
-	}*/
-	arrayHeader.ElementOID = 69053
-	buf = arrayHeader.EncodeBinary(ci, buf)
-	for i := range src {
-		sp := len(buf)
-		buf = pgio.AppendInt32(buf, -1)
-
-		elemBuf, err := src[i].EncodeBinary(ci, buf)
-		if err != nil {
-			return nil, err
-		}
-		if elemBuf != nil {
-			buf = elemBuf
-			pgio.SetInt32(buf[sp:], int32(len(buf[sp:])-4))
-		}
-	}
-
-	return buf, nil
-}
-
 func NewDatabase(ctx context.Context, connString string) (*Db, error) {
 	config, err := pgxpool.ParseConfig(connString)
 	if err != nil {
@@ -81,10 +19,11 @@ func NewDatabase(ctx context.Context, connString string) (*Db, error) {
 	}
 
 	config.AfterConnect = func(ctx context.Context, conn *pgx.Conn) error {
-		_, err := conn.Exec(context.Background(), "SET search_path TO numerus, public")
+		if _, err := conn.Exec(ctx, "SET search_path TO numerus, public"); err != nil {
-		conn.ConnInfo().RegisterDataType(pgtype.DataType{Value: &discountRate{}, Name: "discount_rate", OID: 69002})
 			return err
 		}
+		return registerPgTypes(ctx, conn)
+	}
 
 	config.BeforeAcquire = func(ctx context.Context, conn *pgx.Conn) bool {
 		cookie := ""

pkg/form.go

@@ -48,7 +48,18 @@ func (field *InputField) FillValue(r *http.Request) {
 }
 
 func (field *InputField) Integer() int {
-	value, _ := strconv.Atoi(field.Val)
+	value, err := strconv.Atoi(field.Val)
+	if err != nil {
+		panic(err)
+	}
+	return value
+}
+
+func (field *InputField) Float64() float64 {
+	value, err := strconv.ParseFloat(field.Val, 64)
+	if err != nil {
+		panic(err)
+	}
 	return value
 }
 

pkg/invoices.go

@@ -138,7 +138,7 @@ func HandleAddInvoice(w http.ResponseWriter, r *http.Request, _ httprouter.Param
 			mustRenderNewInvoiceForm(w, r, form)
 			return
 		}
-		conn.MustExec(r.Context(), "select add_invoice($1, $2, $3, $4, $5, $6)", company.Id, form.Number, form.Date, form.Customer, form.Notes, newInvoiceProductArray(form.Products))
+		conn.MustExec(r.Context(), "select add_invoice($1, $2, $3, $4, $5, $6)", company.Id, form.Number, form.Date, form.Customer, form.Notes, NewInvoiceProductArray(form.Products))
 		http.Redirect(w, r, companyURI(company, "/invoices"), http.StatusSeeOther)
 	default:
 		http.Error(w, gettext("Invalid action", locale), http.StatusBadRequest)

pkg/pgtypes.go

@@ -0,0 +1,79 @@
+package pkg
+
+import (
+	"context"
+	"fmt"
+	"github.com/jackc/pgtype"
+	"github.com/jackc/pgx/v4"
+)
+
+type NewInvoiceProductArray []*invoiceProductForm
+
+func (src NewInvoiceProductArray) EncodeBinary(ci *pgtype.ConnInfo, buf []byte) ([]byte, error) {
+	typeName := "new_invoice_product[]"
+	dt, ok := ci.DataTypeForName(typeName)
+	if !ok {
+		return nil, fmt.Errorf("unable to find oid for type name %v", typeName)
+	}
+	var values [][]interface{}
+	for _, form := range src {
+		values = append(values, []interface{}{
+			form.ProductId.Val,
+			form.Name.Val,
+			form.Description.Val,
+			form.Price.Val,
+			form.Quantity.Val,
+			form.Discount.Float64() / 100.0,
+			form.Tax.Selected,
+		})
+	}
+	array := pgtype.NewValue(dt.Value).(pgtype.ValueTranscoder)
+	if err := array.Set(values); err != nil {
+		return nil, err
+	}
+	return array.EncodeBinary(ci, buf)
+}
+
+func registerPgTypes(ctx context.Context, conn *pgx.Conn) error {
+	discountRateOID, err := registerPgType(ctx, conn, &pgtype.Numeric{}, "discount_rate")
+	if err != nil {
+		return err
+	}
+	newInvoiceProduct, err := pgtype.NewCompositeType(
+		"new_invoice_product",
+		[]pgtype.CompositeTypeField{
+			{"product_id", pgtype.Int4OID},
+			{"name", pgtype.TextOID},
+			{"description", pgtype.TextOID},
+			{"price", pgtype.TextOID},
+			{"quantity", pgtype.Int4OID},
+			{"discount_rate", discountRateOID},
+			{"tax", pgtype.Int4ArrayOID},
+		},
+		conn.ConnInfo(),
+	)
+	if err != nil {
+		return err
+	}
+	newInvoiceProductOID, err := registerPgType(ctx, conn, newInvoiceProduct, newInvoiceProduct.TypeName())
+	if err != nil {
+		return err
+	}
+	newInvoiceProductArray := pgtype.NewArrayType("new_invoice_product[]", newInvoiceProductOID, func() pgtype.ValueTranscoder {
+		value := newInvoiceProduct.NewTypeValue()
+		return value.(pgtype.ValueTranscoder)
+	})
+	_, err = registerPgType(ctx, conn, newInvoiceProductArray, newInvoiceProductArray.TypeName())
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func registerPgType(ctx context.Context, conn *pgx.Conn, value pgtype.Value, name string) (oid uint32, err error) {
+	if err = conn.QueryRow(ctx, "select $1::regtype::oid", name).Scan(&oid); err != nil {
+		return
+	}
+	conn.ConnInfo().RegisterDataType(pgtype.DataType{Value: value, Name: name, OID: oid})
+	return
+}