module JsonApiClient
  module Paginating
    class Paginator
      attr_reader :params, :result_set, :links
      def initialize(result_set, links)
        @params = params_for_uri(result_set.uri)
        @result_set = result_set
        @links = links
      end

      def next
        result_set.links.fetch_link("next")
      end

      def prev
        result_set.links.fetch_link("next")
      end

      def first
        result_set.links.fetch_link("first")
      end

      def last
        result_set.links.fetch_link("last")
      end

      def total_pages
        if links["last"]
          last_params = params_for_uri(links["last"])
          last_params.fetch("page") do
            current_page
          end.to_i
        else
          current_page
        end
      end

      # this number may be off
      def total_entries
        per_page * total_pages
      end

      def offset
        per_page * (current_page - 1)
      end

      def per_page
        params.fetch("per_page") do
          result_set.length
        end.to_i
      end

      def current_page
        params.fetch("page", 1).to_i
      end

      def out_of_bounds?
        current_page > total_pages
      end

      def previous_page
        current_page > 1 ? (current_page - 1) : nil
      end

      def next_page
        current_page < total_pages ? (current_page + 1) : nil
      end

      alias limit_value per_page

      protected

      def params_for_uri(uri)
        return {} unless uri
        uri = Addressable::URI.parse(uri)
        uri.query_values || {}
      end
    end
  end
end