# frozen_string_literal: true

module Gitlab
  module Headers
    # Parses link header.
    #
    # @private
    class PageLinks
      HEADER_LINK = 'Link'
      DELIM_LINKS = ','
      LINK_REGEX = /<([^>]+)>; rel="([^"]+)"/
      METAS = %w[last next first prev].freeze

      attr_accessor(*METAS)

      def initialize(headers)
        link_header = headers[HEADER_LINK]

        extract_links(link_header) if link_header && link_header =~ /(next|first|last|prev)/
      end

      private

      def extract_links(header)
        header.split(DELIM_LINKS).each do |link|
          LINK_REGEX.match(link.strip) do |match|
            url = match[1]
            meta = match[2]
            next if !url || !meta || METAS.index(meta).nil?

            send("#{meta}=", url)
          end
        end
      end
    end
  end
end
