From ce71a3a553e586b9d4d9cb80880d2fd7ba9aa134 Mon Sep 17 00:00:00 2001
From: Dmitry Anderson <4nd3r5z0n@gmail.com>
Date: Tue, 12 Nov 2024 14:36:20 +0100
Subject: [PATCH] Select renamed to Query and rewritten

Now it uses pgx.CollectRows build-in method
---
 go.mod   |  1 +
 go.sum   |  2 ++
 pg/pg.go | 54 ++++++++++--------------------------------------------
 3 files changed, 13 insertions(+), 44 deletions(-)

diff --git a/go.mod b/go.mod
index 033dfb2..04a7c58 100644
--- a/go.mod
+++ b/go.mod
@@ -9,6 +9,7 @@ require (
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
 	github.com/jackc/pgx/v5 v5.7.1 // indirect
+	github.com/matchsystems/werr v0.1.3 // indirect
 	go.uber.org/atomic v1.7.0 // indirect
 	golang.org/x/crypto v0.27.0 // indirect
 	golang.org/x/text v0.18.0 // indirect
diff --git a/go.sum b/go.sum
index 3750adf..126ec1a 100644
--- a/go.sum
+++ b/go.sum
@@ -13,6 +13,8 @@ github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 h1:iCEnooe7Ulw
 github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761/go.mod h1:5TJZWKEWniPve33vlWYSoGYefn3gLQRzjfDlhSJ9ZKM=
 github.com/jackc/pgx/v5 v5.7.1 h1:x7SYsPBYDkHDksogeSmZZ5xzThcTgRz++I5E+ePFUcs=
 github.com/jackc/pgx/v5 v5.7.1/go.mod h1:e7O26IywZZ+naJtWWos6i6fvWK+29etgITqrqHLfoZA=
+github.com/matchsystems/werr v0.1.3 h1:h932fzdGLE67w5O8F3O2vO49KkjmSeqsFQqDFkIOMYM=
+github.com/matchsystems/werr v0.1.3/go.mod h1:MpZemBWOQ0IuQogwr5aCjNnIfWe+iEfnSh7nTGQ3M7I=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
diff --git a/pg/pg.go b/pg/pg.go
index 6ad743e..d375644 100644
--- a/pg/pg.go
+++ b/pg/pg.go
@@ -2,25 +2,18 @@ package pgUtils
 
 import (
 	"context"
-	"errors"
-	reflectUtils "git.mic.pp.ua/anderson/nettools/reflect"
 	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
-)
-
-var (
-	ErrEntityNotFound      = errors.New("entity not found")
-	ErrTooManyRows         = errors.New("too many rows")
-	ErrEntityAlreadyExists = errors.New("entity already exists")
-	ErrNoDstFields         = errors.New("no destination fields")
+	"github.com/matchsystems/werr"
 )
 
 type PgxQuerier interface {
 	Query(ctx context.Context, sql string, args ...any) (pgx.Rows, error)
+	QueryRow(ctx context.Context, sql string, args ...any) (pgx.Row, error)
 }
 
-// Select executes query on a provided querier and tries to parse db response
-// Works only with objects
+// Query executes query on a provided querier and tries to parse db response
+// Works only with structs
 //
 // Usage:
 //
@@ -30,44 +23,17 @@ type PgxQuerier interface {
 //	}
 //
 //	db := pgx.Connect(context.Background(), "<url>")
-//	users, err := pgUtils.Select[User](context.Background(), db, "SELECT id, name FROM users")
-func Select[T any](ctx context.Context, db PgxQuerier, query string, args ...any) (out []*T, err error) {
+//	users, err := pgUtils.Query[User](context.Background(), db, "SELECT id, name FROM users")
+func Query[T any](ctx context.Context, db PgxQuerier, query string, args ...any) (out []T, err error) {
 	rows, err := db.Query(ctx, query, args)
 	if err != nil {
-		switch {
-		case errors.Is(err, pgx.ErrNoRows):
-			err = ErrEntityNotFound
-		} // TODO: extend cases
 		return nil, err
 	}
-
-	// Get column names
-	columns := make([]string, len(rows.FieldDescriptions()))
-	for i, fd := range rows.FieldDescriptions() {
-		columns[i] = fd.Name
+	entities, err := pgx.CollectRows(rows, pgx.RowToStructByNameLax[T])
+	if err != nil {
+		return nil, werr.Wrapf(err, "failed to parse query results")
 	}
-	itemFieldPtrs := make([]any, len(columns))
-	out = []*T{}
-
-	defer rows.Close()
-	for rows.Next() {
-		item := new(T)
-		dstItemPtrsMap, err := reflectUtils.GetEntityPtrs(item, "db")
-		if err != nil {
-			return nil, err
-		}
-		for i, columnName := range columns {
-			itemFieldPtrs[i] = dstItemPtrsMap[columnName]
-		}
-		if len(itemFieldPtrs) == 0 {
-			return nil, ErrNoDstFields
-		}
-		if err = rows.Scan(itemFieldPtrs...); err != nil {
-			return out, err
-		}
-		out = append(out, item)
-	}
-	return out, err
+	return entities, nil
 }
 
 // Tx creates new transaction. Cancels it if returned not nil err