Adding a check on the X-Expected-Version header field.

cmd/api/movies.go

@@ -6,6 +6,7 @@ import (
 	"greenlight.craftr.fr/internal/data"
 	"greenlight.craftr.fr/internal/validator"
 	"net/http"
+	"strconv"
 )
 
 // "POST /v1/movies" endpoint.
@@ -108,6 +109,14 @@ func (app *application) updateMovieHandler(w http.ResponseWriter, r *http.Reques
 		return
 	}
 
+	// If the request contains a X-Expected-Version header, verify that the movie version in the database matches the expected version specified in the header.
+	if r.Header.Get("X-Expected-Version") != "" {
+		if strconv.Itoa(int(movie.Version)) != r.Header.Get("X-Expected-Version") {
+			app.editConflictResponse(w, r)
+			return
+		}
+	}
+
 	// Declare an input struct to hold the expected data from the client
 	// Use pointers for the Title, Year and Runtime fields : so we can see if a client has provided a particular key/value pair in the JSON.
 	var input struct {