From ce8dfb1522a98800903df1bd893cd3d0d324aba3 Mon Sep 17 00:00:00 2001
From: lbenedar <lbenedar@local.lab>
Date: Wed, 18 Mar 2026 14:09:48 +0300
Subject: [PATCH] ch8.2

---
 cmd/api/errors.go       |  5 +++++
 cmd/api/movies.go       |  7 ++++++-
 internal/data/models.go |  1 +
 internal/data/movies.go | 15 +++++++++++++--
 4 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/cmd/api/errors.go b/cmd/api/errors.go
index ed507d6..ecd9c30 100644
--- a/cmd/api/errors.go
+++ b/cmd/api/errors.go
@@ -43,3 +43,8 @@ func (app *application) badRequestResponse(w http.ResponseWriter, r *http.Reques
 func (app *application) failedValidationResponse(w http.ResponseWriter, r *http.Request, errors map[string]string) {
 	app.errorResponse(w, r, http.StatusUnprocessableEntity, errors)
 }
+
+func (app *application) editConflictResponse(w http.ResponseWriter, r *http.Request) {
+	message := "unable to update the record due to an edit conflict, please try again"
+	app.errorResponse(w, r, http.StatusConflict, message)
+}
diff --git a/cmd/api/movies.go b/cmd/api/movies.go
index 81a171b..662bc79 100644
--- a/cmd/api/movies.go
+++ b/cmd/api/movies.go
@@ -127,7 +127,12 @@ func (app *application) updateMovieHandler(w http.ResponseWriter, r *http.Reques
 
 	err = app.models.Movies.Update(movie)
 	if err != nil {
-		app.serverErrorResponse(w, r, err)
+		switch {
+		case errors.Is(err, data.ErrEditConflict):
+			app.editConflictResponse(w, r)
+		default:
+			app.serverErrorResponse(w, r, err)
+		}
 		return
 	}
 
diff --git a/internal/data/models.go b/internal/data/models.go
index b549650..6106037 100644
--- a/internal/data/models.go
+++ b/internal/data/models.go
@@ -7,6 +7,7 @@ import (
 
 var (
 	ErrRecordNotFound = errors.New("record not found")
+	ErrEditConflict   = errors.New("edit conflict")
 )
 
 type Models struct {
diff --git a/internal/data/movies.go b/internal/data/movies.go
index 8129ded..d55559c 100644
--- a/internal/data/movies.go
+++ b/internal/data/movies.go
@@ -70,7 +70,7 @@ func (m MovieModel) Update(movie *Movie) error {
 	query := `
 		UPDATE movies
 		SET title=$1, year=$2, runtime=$3, genres=$4, version = version + 1
-		WHERE id = $5
+		WHERE id = $5 AND version = $6
 		RETURNING version`
 
 	args := []any{
@@ -79,9 +79,20 @@ func (m MovieModel) Update(movie *Movie) error {
 		movie.Runtime,
 		pq.Array(movie.Genres),
 		movie.ID,
+		movie.Version,
 	}
 
-	return m.DB.QueryRow(query, args...).Scan(&movie.Version)
+	err := m.DB.QueryRow(query, args...).Scan(&movie.Version)
+	if err != nil {
+		switch {
+		case errors.Is(err, sql.ErrNoRows):
+			return ErrEditConflict
+		default:
+			return err
+		}
+	}
+
+	return nil
 }
 
 func (m MovieModel) Delete(id int64) error {