mastodon/app/models/concerns/paginable.rb

# frozen_string_literal: true

module Paginable
  extend ActiveSupport::Concern

  included do
    scope :paginate_by_max_id, ->(limit, max_id = nil, since_id = nil) {
      query = order(arel_table[:id].desc).limit(limit)
      query = query.where(arel_table[:id].lt(max_id)) if max_id.present?
      query = query.where(arel_table[:id].gt(since_id)) if since_id.present?
      query
    }

    # Differs from :paginate_by_max_id in that it gives the results immediately following min_id,
    # whereas since_id gives the items with largest id, but with since_id as a cutoff.
    # Results will be in ascending order by id.
    scope :paginate_by_min_id, ->(limit, min_id = nil) {
      query = reorder(arel_table[:id]).limit(limit)
      query = query.where(arel_table[:id].gt(min_id)) if min_id.present?
      query
    }

    scope :paginate_by_id, ->(limit, options = {}) {
      if options[:min_id].present?
        paginate_by_min_id(limit, options[:min_id]).reverse
      else
        paginate_by_max_id(limit, options[:max_id], options[:since_id])
      end
    }
  end
end