Refactor: extract populate_messages method for customizable message loading

[xiaohui-zhangxh]

Refactor: Extract populate_messages method for customizable message loading

Extract message population logic into a separate method to enable custom message filtering in subclasses.

Type of change

• Refactor

Description

This refactor extracts the message population logic into a dedicated populate_messages method, allowing subclasses to override message loading behavior. This enables features like agent-based message filtering without modifying the core chat functionality.

Changes

• Extract message population logic to populate_messages method
• Enable custom message filtering through method overriding
• Maintain backward compatibility - no breaking changes

Example Usage

With this refactor, you can implement custom message loading logic:

class Chat
  acts_as_chat

  def with_agent(agent)
    @agent_instruction = messages_association.create!(
      role: :system, 
      agent: agent, 
      content: agent.system_prompt
    )
    with_temperature(agent.temperature)
  end

  def without_agent
    @agent_instruction = nil
    self
  end

  private

  def populate_messages
    @chat.reset_messages!
    messages_association.each do |msg|
      # Skip non-agent system messages when agent is active
      next if @agent_instruction && msg.role == "system" && msg.id != @agent_instruction.id
      
      # Skip agent system messages when no agent is active
      next if @agent_instruction.nil? && msg.agent_id.present?

      @chat.add_message(msg.to_llm)
    end
  end
end

Demo

# Create a gaming expert agent
agent = Agent.create(
  name: "Gaming Expert", 
  system_prompt: "You are a veteran gamer with extensive knowledge of video games. You only discuss gaming-related topics and politely decline non-gaming questions.", 
  temperature: 0.9
)

chat = Chat.last

# With agent - declines non-gaming questions
chat.with_agent(agent).ask("What movies do you recommend?")
# => "I'm here to discuss gaming topics. Is there anything about video games you'd like to talk about?"

# Without agent - answers all questions normally  
chat.without_agent.ask("What is the capital of California?")
# => "The capital of California is Sacramento."

Quality Assurance

• ✅ No breaking changes
• ✅ Existing functionality preserved
• ✅ New customization capability added
• ✅ Backward compatible