fix(backend): tag service not returning any tags without questions

backend/src/main/java/com/group1/programminglanguagesforum/Controllers/QuestionController.java

@@ -1,29 +1,43 @@
 package com.group1.programminglanguagesforum.Controllers;
 
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.NoSuchElementException;
+
+import org.springframework.data.domain.Page;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.DeleteMapping;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.PutMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
 import com.group1.programminglanguagesforum.Constants.EndpointConstants;
 import com.group1.programminglanguagesforum.DTOs.Requests.CreateQuestionRequestDto;
 import com.group1.programminglanguagesforum.DTOs.Requests.DifficultyLevelRequestDto;
 import com.group1.programminglanguagesforum.DTOs.Requests.UpdateQuestionRequestDto;
-import com.group1.programminglanguagesforum.DTOs.Responses.*;
-import com.group1.programminglanguagesforum.Exceptions.ExceptionResponseHandler;
+import com.group1.programminglanguagesforum.DTOs.Responses.CreateQuestionResponseDto;
+import com.group1.programminglanguagesforum.DTOs.Responses.ErrorResponse;
+import com.group1.programminglanguagesforum.DTOs.Responses.GenericApiResponse;
+import com.group1.programminglanguagesforum.DTOs.Responses.GetQuestionDetailsResponseDto;
+import com.group1.programminglanguagesforum.DTOs.Responses.QuestionRateResponseDto;
+import com.group1.programminglanguagesforum.DTOs.Responses.QuestionSummaryDto;
 import com.group1.programminglanguagesforum.Entities.DifficultyLevel;
 import com.group1.programminglanguagesforum.Entities.Question;
+import com.group1.programminglanguagesforum.Exceptions.ExceptionResponseHandler;
 import com.group1.programminglanguagesforum.Exceptions.UnauthorizedAccessException;
 import com.group1.programminglanguagesforum.Services.QuestionDifficultyRateService;
 import com.group1.programminglanguagesforum.Services.QuestionService;
 import com.group1.programminglanguagesforum.Util.ApiResponseBuilder;
-import lombok.RequiredArgsConstructor;
 
-import org.springframework.http.HttpStatus;
-import org.springframework.data.domain.Page;
-import org.springframework.http.ResponseEntity;
-import org.springframework.web.bind.annotation.*;
-
-import java.util.Arrays;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.NoSuchElementException;
+import lombok.RequiredArgsConstructor;
 
 @RestController
 @RequestMapping("/api/v1")
@@ -59,7 +73,8 @@ public ResponseEntity<GenericApiResponse<GetQuestionDetailsResponseDto>> getQues
                     .errorMessage(e.getMessage())
                     .stackTrace(Arrays.toString(e.getStackTrace()))
                     .build();
-            GenericApiResponse<GetQuestionDetailsResponseDto> response = ApiResponseBuilder.buildErrorResponse(GetQuestionDetailsResponseDto.class, e.getMessage(), 404, errorResponse);
+            GenericApiResponse<GetQuestionDetailsResponseDto> response = ApiResponseBuilder
+                    .buildErrorResponse(GetQuestionDetailsResponseDto.class, e.getMessage(), 404, errorResponse);
             return buildResponse(response, org.springframework.http.HttpStatus.NOT_FOUND);
         }
     }
@@ -113,7 +128,7 @@ public ResponseEntity<GenericApiResponse<Map<String, Object>>> searchQuestions(
         Page<Question> questionPage = questionService.searchQuestions(query, tags, difficulty, page, pageSize);
 
         List<QuestionSummaryDto> questionSummaries = questionPage.getContent().stream()
-                .map(questionService::mapToQuestionSummary)
+                .map(QuestionService::mapToQuestionSummary)
                 .toList();
 
         Map<String, Object> response = new HashMap<>();
@@ -142,8 +157,7 @@ public ResponseEntity<GenericApiResponse<QuestionRateResponseDto>> rateQuestion(
             return buildResponse(response, org.springframework.http.HttpStatus.OK);
         } catch (NoSuchElementException e) {
             return ExceptionResponseHandler.NoSuchElementException(e);
-        }
-        catch (UnauthorizedAccessException e) {
+        } catch (UnauthorizedAccessException e) {
             return ExceptionResponseHandler.UnauthorizedAccessException(e);
         }
     }

backend/src/main/java/com/group1/programminglanguagesforum/Repositories/TagRepository.java

@@ -1,25 +1,27 @@
 package com.group1.programminglanguagesforum.Repositories;
 
+import java.util.List;
 
-import com.group1.programminglanguagesforum.Entities.Tag;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
 
-import java.util.List;
+import com.group1.programminglanguagesforum.Entities.Tag;
 
 @Repository
-public interface TagRepository extends JpaRepository<Tag,Long> {
+public interface TagRepository extends JpaRepository<Tag, Long> {
     List<Tag> findAllByIdIn(List<Long> ids);
+
     @Query("SELECT t FROM Tag t " +
-            "JOIN Question q ON t MEMBER OF q.tags " +
+            "LEFT JOIN Question q ON t MEMBER OF q.tags " +
+            "WHERE LOWER(t.tagName) LIKE LOWER(CONCAT('%', :tagName, '%')) " +
             "GROUP BY t.id " +
             "ORDER BY COUNT(q.id) DESC")
-
     Page<Tag> findTagsByTagNameContainingIgnoreCase(String tagName, Pageable pageable);
+
     @Query("SELECT t FROM Tag t JOIN t.followers u WHERE u.id = :userId")
     List<Tag> findTagByFollowers(@Param("userId") Long userId);
 }