# frozen_string_literal: true

##
# Allows us to query Bookmark records for lists. Used mainly
# in the user/activity/bookmarks page.

class BookmarkQuery
  def self.on_preload(&blk)
    (@preload ||= Set.new) << blk
  end

  def self.preload(bookmarks, object)
    preload_polymorphic_associations(bookmarks, object.guardian)
    @preload.each { |preload| preload.call(bookmarks, object) } if @preload
  end

  # These polymorphic associations are loaded to make the UserBookmarkListSerializer's
  # life easier, which conditionally chooses the bookmark serializer to use based
  # on the type, and we want the associations all loaded ahead of time to make
  # sure we are not doing N+1s.
  def self.preload_polymorphic_associations(bookmarks, guardian)
    Bookmark.registered_bookmarkables.each do |registered_bookmarkable|
      registered_bookmarkable.perform_preload(bookmarks, guardian)
    end
  end

  attr_reader :guardian, :count

  def initialize(user:, guardian: nil, search_term: nil, page: nil, per_page: nil)
    @user = user
    @search_term = search_term
    @guardian = guardian || Guardian.new(@user)
    @page = page ? page.to_i : 0
    @per_page = per_page ? per_page.to_i : 20
    @count = 0
  end

  def list_all(&blk)
    ts_query = @search_term.present? ? Search.ts_query(term: @search_term) : nil
    search_term_wildcard = @search_term.present? ? "%#{@search_term}%" : nil

    queries =
      Bookmark
        .registered_bookmarkables
        .map do |bookmarkable|
          interim_results = bookmarkable.perform_list_query(@user, @guardian)

          # this could occur if there is some security reason that the user cannot
          # access the bookmarkables that they have bookmarked, e.g. if they had 1 bookmark
          # on a topic and that topic was moved into a private category
          next if interim_results.blank?

          if @search_term.present?
            interim_results =
              bookmarkable.perform_search_query(interim_results, search_term_wildcard, ts_query)
          end

          # this is purely to make the query easy to read and debug, otherwise it's
          # all mashed up into a massive ball in MiniProfiler :)
          "---- #{bookmarkable.model} bookmarkable ---\n\n #{interim_results.to_sql}"
        end
        .compact

    # same for interim results being blank, the user might have been locked out
    # from all their various bookmarks, in which case they will see nothing and
    # no further pagination/ordering/etc is required
    return [] if queries.empty?

    union_sql = queries.join("\n\nUNION\n\n")
    results = Bookmark.select("bookmarks.*").from("(\n\n#{union_sql}\n\n) as bookmarks")
    results =
      results.order(
        "(CASE WHEN bookmarks.pinned THEN 0 ELSE 1 END),
        bookmarks.reminder_at ASC,
        bookmarks.updated_at DESC",
      )

    @count = results.count

    results = results.offset(@page * @per_page) if @page.positive?

    if updated_results = blk&.call(results)
      results = updated_results
    end

    results = results.limit(@per_page).to_a

    BookmarkQuery.preload(results, self)
    results
  end

  def unread_notifications(limit: 20)
    reminder_notifications =
      Notification
        .for_user_menu(@user.id, limit: [limit, 100].min)
        .unread
        .where(notification_type: Notification.types[:bookmark_reminder])

    # We preload associations like we do above for the list to avoid
    # N1s in the can_see? guardian calls for each bookmark.
    bookmarks =
      Bookmark.where(
        id: reminder_notifications.map { |n| n.data_hash[:bookmark_id] }.compact,
        user: @user,
      )
    BookmarkQuery.preload(bookmarks, self)

    reminder_notifications.select do |n|
      bookmark = bookmarks.find { |bm| bm.id == n.data_hash[:bookmark_id] }
      next if bookmark.blank?
      bookmarkable = Bookmark.registered_bookmarkable_from_type(bookmark.bookmarkable_type)
      bookmarkable.can_see?(@guardian, bookmark)
    end
  end
end