A Pagination Meta Generator for fast_jsonapi gem integration.

pagination_meta_generator.rb

# frozen_string_literal: true

module Driggl
  class PaginationMetaGenerator
    DEFAULT_PAGE = 1
    DEFAULT_PER_PAGE = 20

    def initialize(request:, total_pages:)
      @url = request.base_url + request.path
      @page = (request.params[:page].presence || DEFAULT_PAGE).to_i
      @per_page = request.params[:per_page].to_i
      @total_pages = total_pages
    end

    def call
      links = {}
      if page > 1
        links[:first] = generate_url(1)
        links[:prev] = generate_url(page - 1)
      end
      links[:self] = generate_url(page)
      if page < total_pages
        links[:next] = generate_url(page + 1)
        links[:last] = generate_url(total_pages)
      end
      links
    end

    private

    attr_reader :per_page, :page, :total_pages
    attr_accessor :url

    def generate_url(page)
      [url, url_params(page).presence].compact.join('?')
    end

    def url_params(page)
      url_params = {}
      url_params[:per_page] = per_page if include_per_page?
      url_params[:page] = page if include_page?(page)
      url_params.to_query
    end

    def include_per_page?
      (per_page != 0) && (per_page != DEFAULT_PER_PAGE)
    end

    def include_page?(page)
      (page > 1)
    end
  end
end