feat(session): user in context and transaction as user

pkg/session/user.go

@@ -0,0 +1,53 @@
+package session
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+
+	"github.com/domonda/go-errs"
+	"github.com/domonda/go-sqldb/db"
+	"github.com/domonda/go-types/uu"
+)
+
+type userCtxKeyType struct{}
+
+var userCtxKey userCtxKeyType
+
+func ContextWithUser(ctx context.Context, userID uu.ID) context.Context {
+	return context.WithValue(ctx, userCtxKey, userID)
+}
+
+func UserFromContext(ctx context.Context) (userID uu.ID, err error) {
+	userIDVal := ctx.Value(userCtxKey)
+	userID = uu.IDFrom(userIDVal)
+	if userID == uu.IDNil {
+		return uu.IDNil, errors.New("user not in context")
+	}
+	return userID, nil
+}
+
+func TransactionAsUser(ctx context.Context, txFunc func(ctx context.Context) error) (err error) {
+	return db.Transaction(ctx, func(ctx context.Context) (err error) {
+		userID, err := UserFromContext(ctx)
+		if err != nil {
+			return err
+		}
+
+		// impersonate user in transaction
+		err = db.Conn(ctx).Exec(fmt.Sprintf("set local session.user_id to '%s'; set role viewer;", userID))
+		if err != nil {
+			return err
+		}
+		defer func() {
+			if !errors.Is(err, sql.ErrTxDone) {
+				// for when this transaction is within another one
+				e := db.Conn(ctx).Exec("reset session.user_id; reset role;")
+				err = errs.Combine(err, e)
+			}
+		}()
+
+		return txFunc(ctx)
+	})
+}