Delete category if no other questions have it (triggered when question is deleted)

Author: yuxuanleong

Backend/QuestionService/controllers/questions.js

@@ -17,6 +17,18 @@ questionsRouter.get("/by-category-and-complexity", async (req, res) => {
     }
 });
 
+questionsRouter.get("/by-category", async (req, res) => {
+    const { category } = req.query;
+    try {
+        const query = category ? { category: { $in: [new RegExp(`^${category}$`, "i")] } } : {};
+        const questions = await QuestionModel.find(query);
+        res.status(200).json(questions);
+    } catch (error) {
+        console.error("Error fetching questions by category:", error);
+        res.status(500).json({ error: error.message });
+    }
+});
+
 // Read all questions
 questionsRouter.get("/", async (req, res) => {
     try {

Frontend/src/components/question/Question.jsx

@@ -5,6 +5,7 @@ import ButtonGroup from "react-bootstrap/ButtonGroup";
 import CreateQn from "./CreateQn";
 import EditQn from "./EditQn";
 import questionService from "../../services/questions"
+import categoryService from "../../services/categories"
 
 function Question() {
     const [questions, setQuestions] = useState([]);
@@ -63,16 +64,44 @@ function Question() {
     };
 
     const handleDeleteConfirm = () => {
-        if (questionToDelete) {
-            questionService.deleteQuestion(questionToDelete)
-            .then(res => {
-                console.log(res);
-                setQuestions(questions.filter(question => question._id !== questionToDelete));
-                handleCloseDelete();
+        if (!questionToDelete) return;
+    
+        // retrieve the question to get its categories before deleting
+        questionService.get(questionToDelete)
+            .then((question) => {
+                const categories = question.data.category;
+                console.log("question retrieved: ", question)
+                console.log(`catgories of qn: ${categories}`)
+    
+                // delete the question
+                questionService.deleteQuestion(questionToDelete)
+                    .then(res => {
+                        console.log(res);
+                        
+                       
+                        setQuestions(questions.filter(q => q._id !== questionToDelete));
+                        handleCloseDelete();
+    
+                        // check each category to see if it should be deleted
+                        categories.forEach(async (category) => {
+                            try {
+                                const remainingQuestions = await questionService.getQuestionsByCategory(category);
+                                
+                                // if no other questions have this category, delete the category
+                                if (remainingQuestions.length === 0) {
+                                    await categoryService.deleteCategory(category);
+                                    console.log(`Category ${category} deleted.`);
+                                }
+                            } catch (err) {
+                                console.error(`Error processing category ${category}:`, err);
+                            }
+                        });
+                    })
+                    .catch(err => console.error("Error deleting question:", err));
             })
-            .catch(err => console.log(err));
-        }
+            .catch(err => console.error(`Error fetching question data for ID ${questionToDelete}:`, err));
     };
+    
 
     const renderQuestionsTable = (questions) => {
       const sortedQuestions = [...questions].sort((a, b) => a.id - b.id)

Frontend/src/services/categories.js

@@ -16,9 +16,10 @@ const createCategories = async (newCategories) => {
 };
 
 
-const deleteCategory = async (CategoryId) => {
-    const response = await axios.delete(`${baseCategoryUrl}/${CategoryId}`);
+const deleteCategory = async (categoryName) => {
+    const response = await axios.delete(`${baseCategoryUrl}/${categoryName}`);
     return response.data;
 };
 
+
 export default { getAllCategories, createCategories, deleteCategory };

Frontend/src/services/questions.js

@@ -33,4 +33,4 @@ const deleteQuestion = (id) => {
     return request.then(response => response.data);
 }
 
-export default { getAll, get, createQuestion, updateQuestion, deleteQuestion }
+export default { getAll, get, createQuestion, updateQuestion, deleteQuestion, getQuestionsByCategory }