Select and Tx functions added

.idea/.gitignore

@@ -0,0 +1,8 @@
+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml

.idea/modules.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/.idea/nettools.iml" filepath="$PROJECT_DIR$/.idea/nettools.iml" />
+    </modules>
+  </component>
+</project>

.idea/nettools.iml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="WEB_MODULE" version="4">
+  <component name="Go" enabled="true" />
+  <component name="NewModuleRootManager">
+    <content url="file://$MODULE_DIR$" />
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="" vcs="Git" />
+  </component>
+</project>

go.mod

@@ -1,3 +1,11 @@
 module nettools
 
 go 1.23.1
+
+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
+	golang.org/x/crypto v0.27.0 // indirect
+	golang.org/x/text v0.18.0 // indirect
+)

go.sum

@@ -0,0 +1,17 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
+github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
+github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 h1:iCEnooe7UlwOQYpKFhBabPMi4aNAfoODPEFNiAnClxo=
+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/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=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+golang.org/x/crypto v0.27.0 h1:GXm2NjJrPaiv/h1tb2UH8QfgC/hOf/+z0p6PT8o1w7A=
+golang.org/x/crypto v0.27.0/go.mod h1:1Xngt8kV6Dvbssa53Ziq6Eqn0HqbZi5Z6R0ZpwQzt70=
+golang.org/x/text v0.18.0 h1:XvMDiNzPAl0jr17s6W9lcaIhGUfUORdGCNsuLmPG224=
+golang.org/x/text v0.18.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

pg/pg.go

@@ -0,0 +1,85 @@
+package pgUtils
+
+import (
+	"context"
+	"errors"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+	reflectUtils "nettools/reflect"
+)
+
+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")
+)
+
+type PgxQuerier interface {
+	Query(ctx context.Context, sql string, args ...any) (pgx.Rows, error)
+}
+
+// Select executes query on a provided querier and tries to parse db response into antit
+// Works only with objects
+//
+// Usage:
+//
+//	type User struct {
+//	  id   int
+//	  name string
+//	}
+//
+//	db := pgx.Connect(context.Background(), "<url>")
+//	users, err := pgUtils.Select[User](context.Background(), db, "SELECT * FROM users")
+func Select[T any](ctx context.Context, db PgxQuerier, query string, args ...any) (out []*T, err error) {
+	out = []*T{}
+	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
+	}
+	itemFieldPtrs := make([]interface{}, len(columns))
+
+	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
+}
+
+// Tx creates new transaction. Cancels it if returned not nil err
+func Tx(ctx context.Context, db *pgxpool.Pool, exec func(ctx context.Context, tx pgx.Tx) error) error {
+	tx, err := db.Begin(ctx)
+	if err != nil {
+		return err
+	}
+	err = exec(ctx, tx)
+	if err != nil {
+		_ = tx.Rollback(ctx)
+		return err
+	}
+	return tx.Commit(ctx)
+}

reflect/extract_by_tags.go

@@ -0,0 +1,28 @@
+package reflectUtils
+
+import (
+	"errors"
+	"reflect"
+)
+
+var ErrNilDst = errors.New("destination is nil")
+
+func GetEntityPtrs(dstItem any, tag string) (dstItemPtrsMap map[string]any, err error) {
+	if dstItem == nil {
+		return nil, errors.Join(errors.New("error parsing destination"), ErrNilDst)
+	}
+	v := reflect.ValueOf(dstItem).Elem()
+	t := v.Type()
+
+	dstItemPtrsMap = make(map[string]any)
+	for i := 0; i < t.NumField(); i++ {
+		field := t.Field(i)
+		dbTag := field.Tag.Get(tag)
+		if dbTag != "" {
+			valueField := v.Field(i).Addr().Interface()
+			dstItemPtrsMap[dbTag] = &valueField
+		}
+	}
+
+	return dstItemPtrsMap, nil
+}