# frozen_string_literal: true
class Chat::ChatMessageCreator
  attr_reader :error, :chat_message

  def self.create(opts)
    instance = new(**opts)
    instance.create
    instance
  end

  def initialize(
    chat_channel:,
    in_reply_to_id: nil,
    thread_id: nil,
    user:,
    content:,
    staged_id: nil,
    incoming_chat_webhook: nil,
    upload_ids: nil
  )
    @chat_channel = chat_channel
    @user = user
    @guardian = Guardian.new(user)

    # NOTE: We confirm this exists and the user can access it in the ChatController,
    # but in future the checks should be here
    @in_reply_to_id = in_reply_to_id
    @content = content
    @staged_id = staged_id
    @incoming_chat_webhook = incoming_chat_webhook
    @upload_ids = upload_ids || []
    @thread_id = thread_id
    @error = nil

    @chat_message =
      ChatMessage.new(
        chat_channel: @chat_channel,
        user_id: @user.id,
        last_editor_id: @user.id,
        in_reply_to_id: @in_reply_to_id,
        message: @content,
      )
  end

  def create
    begin
      validate_channel_status!
      uploads = get_uploads
      validate_message!(has_uploads: uploads.any?)
      validate_reply_chain!
      validate_existing_thread!
      @chat_message.thread_id = @existing_thread&.id
      @chat_message.cook
      @chat_message.save!
      create_chat_webhook_event
      create_thread
      @chat_message.attach_uploads(uploads)
      ChatDraft.where(user_id: @user.id, chat_channel_id: @chat_channel.id).destroy_all
      ChatPublisher.publish_new!(@chat_channel, @chat_message, @staged_id)
      Jobs.enqueue(:process_chat_message, { chat_message_id: @chat_message.id })
      Chat::ChatNotifier.notify_new(
        chat_message: @chat_message,
        timestamp: @chat_message.created_at,
      )
      @chat_channel.touch(:last_message_sent_at)
      DiscourseEvent.trigger(:chat_message_created, @chat_message, @chat_channel, @user)
    rescue => error
      @error = error
    end
  end

  def failed?
    @error.present?
  end

  private

  def validate_channel_status!
    return if @guardian.can_create_channel_message?(@chat_channel)

    if @chat_channel.direct_message_channel? && !@guardian.can_create_direct_message?
      raise StandardError.new(I18n.t("chat.errors.user_cannot_send_direct_messages"))
    else
      raise StandardError.new(
              I18n.t("chat.errors.channel_new_message_disallowed.#{@chat_channel.status}"),
            )
    end
  end

  def validate_reply_chain!
    return if @in_reply_to_id.blank?

    @original_message_id = DB.query_single(<<~SQL).last
      WITH RECURSIVE original_message_finder( id, in_reply_to_id )
      AS (
        -- start with the message id we want to find the parents of
        SELECT id, in_reply_to_id
        FROM chat_messages
        WHERE id = #{@in_reply_to_id}

        UNION ALL

        -- get the chain of direct parents of the message
        -- following in_reply_to_id
        SELECT cm.id, cm.in_reply_to_id
        FROM original_message_finder rm
        JOIN chat_messages cm ON rm.in_reply_to_id = cm.id
      )
      SELECT id FROM original_message_finder

      -- this makes it so only the root parent ID is returned, we can
      -- exclude this to return all parents in the chain
      WHERE in_reply_to_id IS NULL;
    SQL

    if @original_message_id.blank?
      raise StandardError.new(I18n.t("chat.errors.original_message_not_found"))
    end

    @original_message = ChatMessage.with_deleted.find_by(id: @original_message_id)
    if @original_message&.trashed?
      raise StandardError.new(I18n.t("chat.errors.original_message_not_found"))
    end
  end

  def validate_existing_thread!
    return if @thread_id.blank?
    @existing_thread = ChatThread.find(@thread_id)

    if @existing_thread.channel_id != @chat_channel.id
      raise StandardError.new(I18n.t("chat.errors.thread_invalid_for_channel"))
    end

    reply_to_thread_mismatch =
      @chat_message.in_reply_to&.thread_id &&
        @chat_message.in_reply_to.thread_id != @existing_thread.id
    original_message_has_no_thread = @original_message && @original_message.thread_id.blank?
    original_message_thread_mismatch =
      @original_message && @original_message.thread_id != @existing_thread.id
    if reply_to_thread_mismatch || original_message_has_no_thread ||
         original_message_thread_mismatch
      raise StandardError.new(I18n.t("chat.errors.thread_does_not_match_parent"))
    end
  end

  def validate_message!(has_uploads:)
    @chat_message.validate_message(has_uploads: has_uploads)
    if @chat_message.errors.present?
      raise StandardError.new(@chat_message.errors.map(&:full_message).join(", "))
    end
  end

  def create_chat_webhook_event
    return if @incoming_chat_webhook.blank?
    ChatWebhookEvent.create(
      chat_message: @chat_message,
      incoming_chat_webhook: @incoming_chat_webhook,
    )
  end

  def get_uploads
    return [] if @upload_ids.blank? || !SiteSetting.chat_allow_uploads

    Upload.where(id: @upload_ids, user_id: @user.id)
  end

  def create_thread
    return if @in_reply_to_id.blank?
    return if @chat_message.thread_id.present?

    thread =
      @original_message.thread ||
        ChatThread.create!(
          original_message: @chat_message.in_reply_to,
          original_message_user: @chat_message.in_reply_to.user,
          channel: @chat_message.chat_channel,
        )

    # NOTE: We intentionally do not try to correct thread IDs within the chain
    # if they are incorrect, and only set the thread ID of messages where the
    # thread ID is NULL. In future we may want some sync/background job to correct
    # any inconsistencies.
    DB.exec(<<~SQL)
      WITH RECURSIVE thread_updater AS (
        SELECT cm.id, cm.in_reply_to_id
        FROM chat_messages cm
        WHERE cm.in_reply_to_id IS NULL AND cm.id = #{@original_message_id}

        UNION ALL

        SELECT cm.id, cm.in_reply_to_id
        FROM chat_messages cm
        JOIN thread_updater ON cm.in_reply_to_id = thread_updater.id
      )
      UPDATE chat_messages
      SET thread_id = #{thread.id}
      FROM thread_updater
      WHERE thread_id IS NULL AND chat_messages.id = thread_updater.id
    SQL

    @chat_message.thread_id = thread.id
  end
end