feat: update changes, race condition check on version, put -> patch

projects/greenlight/internal/data/models.go

@@ -9,6 +9,7 @@ import (
 // looking up a movie that doesn't exist in our database.
 var (
 	ErrRecordNotFound = errors.New("record not found")
+	ErrEditConflict   = errors.New("edit conflict")
 )
 
 // Create a Models struct which wraps the MovieModel. We'll add other models to this,

projects/greenlight/internal/data/movies.go

@@ -86,7 +86,7 @@ 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`
 
 	// Create an args slice containing the values for the placeholder parameters.
@@ -96,11 +96,22 @@ func (m MovieModel) Update(movie *Movie) error {
 		movie.Runtime,
 		pq.Array(movie.Genres),
 		movie.ID,
+		movie.Version,
 	}
 
 	// Use the QueryRow() method to execute the query, passing in the args slice as a
 	// variadic parameter and scanning the new version value into the movie struct.
-	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 {