Add isEnrolled handler

Author: zachspang

backend/internal/handlers/courses.go

@@ -196,6 +196,30 @@ func CreateCourse(c *fiber.Ctx) error {
 	})
 }
 
+// Returns a true if user is enrolled in course
+func IsEnrolled(c *fiber.Ctx) error {
+	course_id := c.Params("course_id")
+	user_id := c.Params("user_id")
+
+	var count int64
+	
+	if err := database.DB.Table("enrollment").Where("account_id = ? AND course_id = ?", user_id, course_id).Count(&count).Error; err != nil {
+		return c.Status(fiber.StatusNotFound).JSON(fiber.Map{"error": "Error retrieving courses"})
+	}
+	
+	if count > 0 {
+		return c.JSON(fiber.Map{
+			"message": "User is enrolled in this course",
+			"isEnrolled": true,
+		})
+	} else {
+		return c.JSON(fiber.Map{
+			"message": "User is not enrolled in this course",
+			"isEnrolled": false,
+		})
+	}
+}
+
 // Enroll user into course
 func Enroll(c *fiber.Ctx) error {
 	user_id := c.Params("user_id")

backend/internal/router/route.go

@@ -91,6 +91,7 @@ func SetupRoutes(app *fiber.App) {
 	app.Post("/delete-file/:creator_id/:content_id", handlers.DeleteFile)
 	app.Post("/edit-content/:creator_id/:content_id", handlers.EditContent)
 	app.Post("/edit-thumbnail/:creator_id/:course_id", handlers.EditThumbnail)
+	app.Get("/is-enrolled/:user_id/:course_id", handlers.IsEnrolled)
 	app.Post("/enroll/:user_id/:course_id", handlers.Enroll)
 	app.Delete("/unenroll/:user_id/:course_id", handlers.Unenroll)
 }

frontend/src/components/pages/Course.js

@@ -10,7 +10,7 @@ export function Course() {
     const [userInfo, setUserInfo]     = useState(null);
     const [error, setError]           = useState(null);
     const [file, setFile]               = useState(null);
-    const [isEnrolled, setIsEnrolled] = useState(false);
+    const [isEnrolled, setIsEnrolled] = useState(null);
     const [newContentName, setNewContentName] = useState({
         title: "",
     });
@@ -212,12 +212,25 @@ export function Course() {
             .catch((error) => setError(error.message));
         }
 
+        async function fetchIsEnrolled() {
+            await fetch(`http://localhost:4000/is-enrolled/${userId}/${courseID}`)
+            .then((response) => {
+                if (!response.ok) {
+                    throw new Error('Network response was not ok');
+                }
+                return response.json();
+            })
+            .then((data) => setIsEnrolled(data.isEnrolled))
+            .catch((error) => setError(error.message));
+        }
+
         fetchCourse();
         fetchUser();
+        fetchIsEnrolled();
     }, [courseID]);
 
     if (error) return <p>Error: {error}</p>;
-    if (!courseInfo || !userInfo) return <p>Loading...</p>;
+    if (!courseInfo || !userInfo || isEnrolled === null) return <p>Loading...</p>;
 
     var moduleList = [];
     //Push all modules into moduleList