pagination.rb

module Pagination
  extend ActiveSupport::Concern

  included do
    before_action :set_v2_default_pagination_params, if: -> do
      request.fullpath.include?('v2') && action_name == 'index'
    end
  end

  def paginated_collection(collection)
    collection.page(params[:page]).per(params[:per_page])
  end

  def v2_paginated_collection(resources)
    data = resources.scope.instance_variable_get(:@unpaginated_object)
    data.page(params[:page][:number]).per(params[:page][:size])
  end

  def set_v2_default_pagination_params
    params[:page] ||= {
      number: 1,
      size: per_page
    }
  end

  def pagination_links(collection, class_name = nil)
    {
      "self": current_page_link(collection, class_name.to_s),
      "first": first_page_link(collection, class_name.to_s),
      "prev": prev_page_link(collection, class_name.to_s),
      "next": next_page_link(collection, class_name.to_s),
      "last": last_page_link(collection, class_name.to_s)
    }
  end

  def current_page_link(collection, class_name = nil)
    pages = { page: collection.current_page, per_page: per_page }
    url_for_collection(collection, class_name, pages)
  end

  def first_page_link(collection, class_name = nil)
    pages = { page: 1, per_page: per_page }
    url_for_collection(collection, class_name, pages)
  end

  def last_page_link(collection, class_name = nil)
    pages = { page: collection.total_pages, per_page: per_page }
    url_for_collection(collection, class_name, pages)
  end

  def prev_page_link(collection, class_name = nil)
    potential_prev_page = collection.current_page - 1
    prev_page = potential_prev_page >= 1 ? potential_prev_page : nil

    return nil if prev_page.nil?

    pages = { page: prev_page, per_page: per_page }
    url_for_collection(collection, class_name, pages)
  end

  def next_page_link(collection, class_name = nil)
    potential_next_page = collection.current_page + 1
    next_page = potential_next_page <= collection.total_pages ? potential_next_page : nil

    return nil if next_page.nil?

    pages = { page: next_page, per_page: per_page }
    url_for_collection(collection, class_name, pages)
  end

  def url_for_collection(collection, class_name = nil, pagination = {})
    if collection.exists?
      model_name = collection.first.class.name
    else
      model_name = class_name
    end

    resource = model_name.underscore.downcase.pluralize
    send("#{resource}_url", incoming_params.merge(pagination))
  end

  def pages_meta(collection)
    {
      total_count: collection.total_count,
      total_pages: collection.total_pages,
      current_page: collection.current_page,
      per_page: per_page
    }.transform_keys { |k| k.to_s.gsub('_', '-') }
  end

  def per_page
    return @per_page if @per_page
    @per_page = params[:per_page].to_i

    if @per_page > Kaminari.config[:default_per_page] || @per_page == 0
      @per_page = Kaminari.config[:default_per_page]
    else
      @per_page
    end
  end

  def incoming_params
    params.slice(:include, :filter).to_unsafe_h
  end
end