# frozen_string_literal: true

module Chat
  module Service
    # Service responsible for updating the last read message id of a membership.
    #
    # @example
    #  Chat::Service::UpdateUserLastRead.call(user_id: 1, channel_id: 2, message_id: 3, guardian: guardian)
    #
    class UpdateUserLastRead
      include Base

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

      contract
      model :membership, :fetch_active_membership
      policy :invalid_access
      policy :ensure_message_id_recency
      policy :ensure_message_exists
      step :update_last_read_message_id
      step :mark_associated_mentions_as_read
      step :publish_new_last_read_to_clients

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

        validates :message_id, :user_id, :channel_id, presence: true
      end

      private

      def fetch_active_membership(user_id:, channel_id:, **)
        UserChatChannelMembership.includes(:user, :chat_channel).find_by(
          user_id: user_id,
          chat_channel_id: channel_id,
          following: true,
        )
      end

      def invalid_access(guardian:, membership:, **)
        guardian.can_join_chat_channel?(membership.chat_channel)
      end

      def ensure_message_id_recency(message_id:, membership:, **)
        !membership.last_read_message_id || message_id >= membership.last_read_message_id
      end

      def ensure_message_exists(channel_id:, message_id:, **)
        ChatMessage.with_deleted.exists?(chat_channel_id: channel_id, id: message_id)
      end

      def update_last_read_message_id(message_id:, membership:, **)
        membership.update!(last_read_message_id: message_id)
      end

      def mark_associated_mentions_as_read(membership:, message_id:, **)
        Notification
          .where(notification_type: Notification.types[:chat_mention])
          .where(user: membership.user)
          .where(read: false)
          .joins("INNER JOIN chat_mentions ON chat_mentions.notification_id = notifications.id")
          .joins("INNER JOIN chat_messages ON chat_mentions.chat_message_id = chat_messages.id")
          .where("chat_messages.id <= ?", message_id)
          .where("chat_messages.chat_channel_id = ?", membership.chat_channel.id)
          .update_all(read: true)
      end

      def publish_new_last_read_to_clients(guardian:, channel_id:, message_id:, **)
        ChatPublisher.publish_user_tracking_state(guardian.user, channel_id, message_id)
      end
    end
  end
end