From e9cfbe311050b64b32c7941247b71251cf9d0b86 Mon Sep 17 00:00:00 2001
From: ozdentarikcan <ozdentarikcan@gmail.com>
Date: Mon, 16 Dec 2024 10:59:32 +0300
Subject: [PATCH] Add recommendation query

---
 .../Repositories/QuestionRepository.java         | 16 ++++++++++++++++
 .../Services/QuestionService.java                | 12 ++++++++++--
 .../Services/UserService.java                    |  6 ++++++
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/backend/src/main/java/com/group1/programminglanguagesforum/Repositories/QuestionRepository.java b/backend/src/main/java/com/group1/programminglanguagesforum/Repositories/QuestionRepository.java
index 42120529..58c541d2 100644
--- a/backend/src/main/java/com/group1/programminglanguagesforum/Repositories/QuestionRepository.java
+++ b/backend/src/main/java/com/group1/programminglanguagesforum/Repositories/QuestionRepository.java
@@ -31,6 +31,22 @@ Page<Question> searchQuestions(
             @Param("difficulty") DifficultyLevel difficulty,
             Pageable pageable);
 
+    @Query("SELECT DISTINCT q FROM Question q " +
+           "LEFT JOIN q.tags t " +
+           "WHERE (:query IS NULL OR " +
+           "      LOWER(q.title) LIKE LOWER(CONCAT('%', :query, '%')) OR " +
+           "      LOWER(q.questionBody) LIKE LOWER(CONCAT('%', :query, '%'))) " +
+           "AND (:tagIds IS NULL OR t.id IN :tagIds) " +
+           "AND (:difficulty IS NULL OR q.difficulty = :difficulty) " +
+           "ORDER BY " +
+           "    CASE WHEN :authorIds IS NOT NULL AND q.askedBy.id IN :authorIds THEN 1 ELSE 0 END DESC")
+    Page<Question> searchQuestionsByRecommended(
+            @Param("query") String query,
+            @Param("authorIds") List<Long> authorIds,
+            @Param("tagIds") List<Long> tagIds,
+            @Param("difficulty") DifficultyLevel difficulty,
+            Pageable pageable);
+
     @Query("SELECT q FROM Question q WHERE q.askedBy.id = :author")
     List<Question> findByAuthorId(@Param("author") Long authorId);
 
diff --git a/backend/src/main/java/com/group1/programminglanguagesforum/Services/QuestionService.java b/backend/src/main/java/com/group1/programminglanguagesforum/Services/QuestionService.java
index 6db81f66..a9613530 100644
--- a/backend/src/main/java/com/group1/programminglanguagesforum/Services/QuestionService.java
+++ b/backend/src/main/java/com/group1/programminglanguagesforum/Services/QuestionService.java
@@ -218,7 +218,9 @@ public Page<Question> searchQuestions(
                         String tagIdsStr,
                         DifficultyLevel difficulty,
                         int page,
-                        int pageSize) {
+                        int pageSize,
+                        String sort,
+                        User currentUser) {
 
                 List<Long> tagIds = null;
                 if (tagIdsStr != null && !tagIdsStr.isEmpty()) {
@@ -228,7 +230,13 @@ public Page<Question> searchQuestions(
                 }
 
                 PageRequest pageable = PageRequest.of(page - 1, pageSize);
-                return questionRepository.searchQuestions(query, tagIds, difficulty, pageable);
+                if (Objects.equals(sort, "default") || Objects.equals(currentUser, null)) {
+                        return questionRepository.searchQuestions(query, tagIds, difficulty, pageable);
+                } else {
+                        List<Long> authorIds = getFollowingIds(currentUser);
+                        return questionRepository.searchQuestionsByRecommended(query, authorIds, tagIds, difficulty, pageable);
+                }
+                
         }
 
         public static QuestionSummaryDto mapToQuestionSummary(Question question) {
diff --git a/backend/src/main/java/com/group1/programminglanguagesforum/Services/UserService.java b/backend/src/main/java/com/group1/programminglanguagesforum/Services/UserService.java
index 646ba34e..3fe8307c 100644
--- a/backend/src/main/java/com/group1/programminglanguagesforum/Services/UserService.java
+++ b/backend/src/main/java/com/group1/programminglanguagesforum/Services/UserService.java
@@ -107,4 +107,10 @@ public Page<User> searchUsers(String query, int page, int pageSize) {
     public List<User> getFollowing(User user) {
         return user.getFollowing().stream().toList();
     }
+
+    public List<Long> getFollowingIds(User user) {
+        return user.getFollowing().stream()
+                   .map(User::getId) // Map each User to its ID
+                   .collect(Collectors.toList()); // Collect the IDs into a List
+    }
 }