feat : add "problem of the day" endpoint

Author: Rajat069

README.md

@@ -84,10 +84,12 @@ All endpoints are relative to the base path `/api/v1`.
 **Base Path**: `/api/v1/questions`
 
 | Method | Endpoint | Description |
-|--------|----------|-------------|
+|--------|--------|-------------|
 | GET | `/` | Get a paginated list of all questions from the local database. Supports `?page=`, `&size=`, and `&sort=`. |
+| GET | `/potd` | Get the current LeetCode Problem of the Day (POTD). |
 | POST | `/search` | A powerful search endpoint. See request body details below. |
 
+
 #### POST /search Request Body
 
 This endpoint allows for complex filtering and sorting of questions stored in the API's database.

src/main/java/com/rajat_singh/leetcode_api/client/LeetCodeClient.java

@@ -272,4 +272,16 @@ public UserLeetCodeCalendarResponse fetchUserLeetCodeCalendar(String username, i
         return restTemplate.postForObject(leetcodeApiUrl,entity,UserLeetCodeCalendarResponse.class);
     }
 
+    @RateLimiter(name = "leetcode-api")
+    public DailyCodingChallengeResponse fetchDailyCodingChallengeQuestions() {
+        HttpHeaders headers = new HttpHeaders();
+        setHeader(headers);
+
+        Map<String,Object> requestBody = new HashMap<>();
+        requestBody.put("query", FETCH_POTD);
+
+        HttpEntity<Map<String ,Object>> entity = new HttpEntity<>(requestBody, headers);
+        return restTemplate.postForObject(leetcodeApiUrl,entity,DailyCodingChallengeResponse.class);
+    }
+
 }

src/main/java/com/rajat_singh/leetcode_api/controller/LeetCodeQuestionsController.java

@@ -54,5 +54,17 @@ public ResponseEntity<Page<QuestionResponseDTO>> getAllQuestions(Pageable pageab
         return ResponseEntity.ok(dtoPage);
     }
 
+    @GetMapping("/potd")
+    public ResponseEntity<QuestionResponseDTO> getPotd() {
+        Logger.info("Fetching POTD from database");
+        QuestionEntity potd = questionsRepository.findByIsProblemOfTheDayTrue();
+        if (potd == null) {
+            Logger.warn("No problem of the day found");
+            return ResponseEntity.notFound().build();
+        }
+        QuestionResponseDTO dto = questionMapper.entityToResponseDTO(potd);
+        return ResponseEntity.ok(dto);
+    }
+
 
 }

src/main/java/com/rajat_singh/leetcode_api/dto/DailyCodingChallengeResponse.java

@@ -0,0 +1,27 @@
+package com.rajat_singh.leetcode_api.dto;
+
+import lombok.Data;
+
+@Data
+public class DailyCodingChallengeResponse {
+    public DataNode data;
+
+    @Data
+    public static class DataNode {
+        public ActiveDailyCodingChallengeQuestion activeDailyCodingChallengeQuestion;
+    }
+
+    @Data
+    public static class ActiveDailyCodingChallengeQuestion {
+        private String date;
+        private String link;
+        private Question question;
+    }
+
+    @Data
+    public static class Question {
+        private String title;
+        private String titleSlug;
+    }
+
+}

src/main/java/com/rajat_singh/leetcode_api/entity/QuestionEntity.java

@@ -26,4 +26,5 @@ public class QuestionEntity {
     )
     private List<TopicTag> topicTags = new ArrayList<>();
     String problemUrl;
+    Boolean isProblemOfTheDay;
 }

src/main/java/com/rajat_singh/leetcode_api/graphql/GraphQlQueries.java

@@ -286,5 +286,17 @@ query userProfileCalendar($username: String!, $year: Int) {
             }
            """;
 
+    public static final String FETCH_POTD = """
+            query questionOfToday {
+              activeDailyCodingChallengeQuestion {
+                date
+                link
+                question {
+                  titleSlug
+                }
+              }
+            }
+            """;
+
 
 }

src/main/java/com/rajat_singh/leetcode_api/repository/QuestionsRepository.java

@@ -10,5 +10,6 @@
 public interface QuestionsRepository extends JpaRepository<QuestionEntity,Integer>, JpaSpecificationExecutor<QuestionEntity> {
 
     QuestionEntity findByTitleSlug(String title);
+    QuestionEntity findByIsProblemOfTheDayTrue();
 
 }

src/main/java/com/rajat_singh/leetcode_api/scheduler/LeetCodeSyncScheduler.java

@@ -1,11 +1,13 @@
 package com.rajat_singh.leetcode_api.scheduler;
 
 import com.rajat_singh.leetcode_api.client.LeetCodeClient;
+import com.rajat_singh.leetcode_api.dto.DailyCodingChallengeResponse;
 import com.rajat_singh.leetcode_api.dto.QuestionListResponse;
 import com.rajat_singh.leetcode_api.entity.QuestionEntity;
 import com.rajat_singh.leetcode_api.entity.TopicTag;
 import com.rajat_singh.leetcode_api.mappers.QuestionMapper;
 import com.rajat_singh.leetcode_api.repository.QuestionsRepository;
+import jakarta.annotation.PostConstruct;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.scheduling.annotation.Async;
 import org.springframework.scheduling.annotation.Scheduled;
@@ -88,4 +90,26 @@ public void syncAcRateData() {
         Long endTime = System.currentTimeMillis();
         Logger.info("LeetCode [AC Rate] sync completed in {} seconds.", (endTime - startTime) / 1000);
     }
+
+    @Scheduled(cron = "0 31 5 * * ?", zone = "Asia/Kolkata") // Runs every day at 5:31 AM (IST) for POTD sync
+    @Async
+    public void syncPOTD() {
+        Logger.info("Starting LeetCode [POTD] sync... at {}", DateFormat.getDateInstance().format(System.currentTimeMillis()));
+        Long startTime = System.currentTimeMillis();
+        DailyCodingChallengeResponse response = leetCodeApiClient.fetchDailyCodingChallengeQuestions();
+
+        QuestionEntity existingQuestion = questionRepository.findByTitleSlug(response.getData().getActiveDailyCodingChallengeQuestion().getQuestion().getTitleSlug());
+        if(Objects.nonNull(existingQuestion)){
+                existingQuestion.setIsProblemOfTheDay(true);
+                questionRepository.save(existingQuestion);
+        }
+
+        Long endTime = System.currentTimeMillis();
+        Logger.info("LeetCode [POTD] sync completed in {} seconds.", (endTime - startTime) / 1000);
+    }
+
+    @PostConstruct
+    public void initialSync() {
+        syncPOTD();
+    }
 }