feat: added db transactions abstraction; cleaned up user registration; repos adapted new abstraction: all repos now support transactions, if present in ctx

internal/repository/repo.go

@@ -0,0 +1,73 @@
+package repository
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"sync/atomic"
+)
+
+type Transaction interface {
+	ExecContext(ctx context.Context, query string, args ...any) (sql.Result, error)
+	QueryContext(ctx context.Context, query string, args ...any) (*sql.Rows, error)
+	QueryRowContext(ctx context.Context, query string, args ...any) *sql.Row
+	PrepareContext(ctx context.Context, query string) (*sql.Stmt, error)
+}
+
+type Repo struct {
+	*Transactor
+}
+
+func NewRepo(t *Transactor) Repo {
+	return Repo{t}
+}
+
+func (r *Repo) conn(ctx context.Context) Transaction {
+	if tx, ok := ctx.Value(txKey{}).(*sql.Tx); ok {
+		return tx
+	}
+	return r.db
+}
+
+type txKey struct{}
+
+type Transactor struct {
+	db *sql.DB
+	sp atomic.Uint64
+}
+
+func NewTransactor(db *sql.DB) *Transactor {
+	return &Transactor{db: db, sp: atomic.Uint64{}}
+}
+
+func (t *Transactor) WithinTx(ctx context.Context, fn func(context.Context) error) error {
+	if tx, ok := ctx.Value(txKey{}).(*sql.Tx); ok {
+		return t.withinSavepoint(ctx, tx, fn)
+	}
+
+	tx, err := t.db.BeginTx(ctx, nil)
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+
+	if err = fn(ctx); err != nil {
+		return err
+	}
+	return tx.Commit()
+}
+
+func (t *Transactor) withinSavepoint(ctx context.Context, tx *sql.Tx, fn func(context.Context) error) error {
+	name := fmt.Sprintf("sp_%d", t.sp.Add(1))
+	if _, err := tx.ExecContext(ctx, "SAVEPOINT "+name); err != nil {
+		return err
+	}
+
+	if err := fn(ctx); err != nil {
+		_, _ = tx.ExecContext(ctx, "ROLLBACK TO SAVEPOINT"+name)
+		return err
+	}
+
+	_, err := tx.ExecContext(ctx, "RELEASE SAVEPOINT"+name)
+	return err
+}