Add method to get messages from a conversation

app/persistence/repository/messages.rb

@@ -66,6 +66,20 @@ def find_conversations(profile_id:)
                        .to_a
         end
 
+        # Returns the last 20 messages from a conversation
+        # @param conversation_id (see .insert_message)
+        # @param max_id [Integer, nil] Used for pagination, will only look for messages with id smaller than the given one
+        # @return [Array<Hash>]
+        def find_messages(conversation_id:, max_id: nil)
+          # TODO: (renatolond, 2024-11-20) I think this needs an index to support this query, look into it
+          m = messages.where(conversation_id:)
+                      .order(Sequel[:id].desc)
+                      .limit(20)
+
+          m = m.where { id < max_id } if max_id
+          m.to_a
+        end
+
         private
 
           # @return [Sequel::Postgres::Dataset]

test/app/persistence/repository/messages_test.rb

@@ -94,4 +94,31 @@
       assert_equal 2, conversations.size
     end
   end
+
+  describe ".find_messages" do
+    before do
+      create(:message, conversation: @conversation, sender: "profile1", content: "Message 1")
+      create(:message, conversation: @conversation, sender: "profile2", content: "Message 2")
+      @message3 = create(:message, conversation: @conversation, sender: "profile1", content: "Message 3")
+      create(:message, conversation: @conversation, sender: "profile1", content: "Message 4")
+      create(:message, conversation: @conversation, sender: "profile2", content: "Message 5")
+    end
+
+    it "find all messages for a conversation" do
+      messages = Persistence::Repository::Messages.find_messages(conversation_id: @conversation.id)
+      expected_messages = ["Message 5", "Message 4", "Message 3", "Message 2", "Message 1"]
+
+      assert_equal 5, messages.size
+      assert_equal(expected_messages, messages.map { |v| v[:content] })
+    end
+
+    it "paginate messages for a conversation" do
+      messages = Persistence::Repository::Messages.find_messages(conversation_id: @conversation.id, max_id: @message3.id)
+
+      expected_messages = ["Message 2", "Message 1"]
+
+      assert_equal 2, messages.size
+      assert_equal(expected_messages, messages.map { |v| v[:content] })
+    end
+  end
 end