sure/app/controllers/messages_controller.rb

class MessagesController < ApplicationController
  guard_feature unless: -> { Current.user.ai_enabled? }

  before_action :set_chat

  def create
    @message = UserMessage.new(
      chat: @chat,
      content: message_params[:content],
      ai_model: message_params[:ai_model].presence || Chat.default_model
    )

    if @message.save
      redirect_to chat_path(@chat, thinking: true)
    else
      redirect_to chat_path(@chat), alert: @message.errors.full_messages.to_sentence
    end
  rescue ActiveRecord::InvalidForeignKey
    redirect_to chats_path, alert: t(".chat_not_found")
  end

  # Called by the chat watchdog when an assistant "Thinking…" bubble has waited
  # too long for a response that never arrived. Idempotent and scoped to the
  # current user's chat.
  def report_timeout
    message = @chat.messages.find(params[:id])
    @chat.handle_undelivered_response!(message)
    head :ok
  rescue ActiveRecord::RecordNotFound
    head :not_found
  end

  private
    def set_chat
      @chat = Current.user.chats.find(params[:chat_id])
    end

    def message_params
      params.require(:message).permit(:content, :ai_model)
    end
end