FIX: User directory for solutions should update when value changes from positive value to zero (#372)

# bug
If John created a post which is a solution in March, the user directory would show that John solution = 1.
In April, if John has not solved a topic, he would still have solution = 1 in the user directory.

# fix
reset solutions to 0 before updating

plugin.rb

@@ -290,6 +290,10 @@ after_initialize do
   end
 
   query = <<~SQL
+    UPDATE directory_items di
+       SET solutions = 0
+     WHERE di.period_type = :period_type AND di.solutions IS NOT NULL;
+
     WITH x AS (
       SELECT p.user_id, COUNT(DISTINCT st.id) AS solutions
       FROM discourse_solved_solved_topics AS st
@@ -310,11 +314,10 @@ after_initialize do
       GROUP BY p.user_id
     )
     UPDATE directory_items di
-    SET solutions = x.solutions
-    FROM x
-    WHERE x.user_id = di.user_id
-      AND di.period_type = :period_type
-      AND di.solutions <> x.solutions
+       SET solutions = x.solutions
+      FROM x
+     WHERE x.user_id = di.user_id
+       AND di.period_type = :period_type;
   SQL
 
   add_directory_column("solutions", query:)

spec/models/directory_item_spec.rb

@@ -101,5 +101,32 @@ describe DirectoryItem, type: :model do
         ).solutions,
       ).to eq(1)
     end
+
+    context "when refreshing across dates" do
+      it "updates the user's solution count from 1 to 0" do
+        freeze_time 40.days.ago
+        DiscourseSolved.accept_answer!(topic_post1, Discourse.system_user)
+
+        DirectoryItem.refresh!
+
+        expect(
+          DirectoryItem.find_by(
+            user_id: user.id,
+            period_type: DirectoryItem.period_types[:monthly],
+          ).solutions,
+        ).to eq(1)
+
+        unfreeze_time
+
+        DirectoryItem.refresh!
+
+        expect(
+          DirectoryItem.find_by(
+            user_id: user.id,
+            period_type: DirectoryItem.period_types[:monthly],
+          ).solutions,
+        ).to eq(0)
+      end
+    end
   end
 end