# frozen_string_literal: true

module Chat
  module Service
    # Finds a thread within a channel. The thread_id and channel_id must
    # match. For now we do not want to allow fetching threads if the
    # enable_experimental_chat_threaded_discussions hidden site setting
    # is not turned on, and the channel must specifically have threading
    # enabled.
    #
    # @example
    #  Chat::Service::LookupThread.call(thread_id: 88, channel_id: 2, guardian: guardian)
    #
    class LookupThread
      include Base

      # @!method call(thread_id:, channel_id:, guardian:)
      #   @param [Integer] thread_id
      #   @param [Integer] channel_id
      #   @param [Guardian] guardian
      #   @return [Chat::Service::Base::Context]

      policy :threaded_discussions_enabled
      contract
      model :thread, :fetch_thread
      policy :invalid_access
      policy :threading_enabled_for_channel

      # @!visibility private
      class Contract
        attribute :thread_id, :integer
        attribute :channel_id, :integer

        validates :thread_id, :channel_id, presence: true
      end

      private

      def threaded_discussions_enabled
        SiteSetting.enable_experimental_chat_threaded_discussions
      end

      def fetch_thread(contract:, **)
        ChatThread.includes(
          :channel,
          original_message_user: :user_status,
          original_message: :chat_webhook_event,
        ).find_by(id: contract.thread_id, channel_id: contract.channel_id)
      end

      def invalid_access(guardian:, thread:, **)
        guardian.can_preview_chat_channel?(thread.channel)
      end

      def threading_enabled_for_channel(thread:, **)
        thread.channel.threading_enabled
      end
    end
  end
end