Fix context updates

app/models/chat.rb

@@ -73,15 +73,15 @@ def generate_story
   def context(ids = nil)
     size = Rails.configuration.secrets[:context_size]
     current = RedisService.lrange(redis_context_path, 0, size).map(&:to_i)
-    return current.shuffle if ids.nil?
+    return current if ids.nil?
 
-    uniq_ids = ids.uniq
-    current -= uniq_ids
-    current.unshift(*uniq_ids)
+    uniq_ids = ids.map(&:to_i).uniq
+    current = (uniq_ids | current).compact_blank.first(size)
     RedisService.multi do |r|
       r.del(redis_context_path)
-      r.lpush(redis_context_path, current.first(size))
+      r.lpush(redis_context_path, current)
     end
+    current
   end
 
   private

app/services/redis_service.rb

@@ -6,6 +6,6 @@ def connection
       @connection ||= Redis.new(Rails.configuration.secrets[:cache_redis])
     end
 
-    delegate :multi, :lrange, :set, :get, :incr, :decr, to: :connection
+    delegate :del, :ltrim, :lpush, :rpush, :multi, :lrange, :set, :get, :incr, :decr, to: :connection
   end
 end

spec/models/chat_spec.rb

@@ -17,6 +17,57 @@
     expect(chat).to be_valid
   end
 
+  describe '#context' do
+    subject(:method_call) { chat.context(new_ids) }
+
+    let(:redis_key) { "chat_context/#{chat.id}" }
+    let(:old_ids)   { %w[4 5 6 2] }
+
+    after { RedisService.del(redis_key) }
+
+    context 'when new ids absend' do
+      let(:new_ids) { nil }
+
+      context 'when context is empty' do
+        it 'returns empty array' do
+          expect(method_call).to eq []
+        end
+      end
+
+      context 'when context is not empty' do
+        before { RedisService.lpush(redis_key, old_ids) }
+
+        it 'returns empty array' do
+          expect(method_call).to match_array old_ids.map(&:to_i)
+        end
+      end
+    end
+
+    context 'when new ids present' do
+      let(:new_ids) { %w[1 2 3 4] }
+
+      context 'when context is empty' do
+        before { RedisService.del(redis_key) }
+
+        it 'adds new context' do
+          method_call
+          result = RedisService.lrange(redis_key, 0, 50)
+          expect(result).to match_array new_ids
+        end
+      end
+
+      context 'when context has smth' do
+        before { RedisService.lpush(redis_key, old_ids) }
+
+        it 'merges context' do
+          method_call
+          result = RedisService.lrange(redis_key, 0, 50)
+          expect(result).to match_array(new_ids | old_ids)
+        end
+      end
+    end
+  end
+
   describe '#choose_winner!' do
     subject(:method_call) { chat.choose_winner! }