pagination.rb

require 'json'

class Pagination
  attr_reader :limit, :offset, :total

  def initialize(options={})
    @limit  = options[:per_page] ? options[:per_page] : options[:limit]
    @offset = options[:page] ? (options[:page] * @limit) : options[:offset]
    @total  = options[:total_entries] ? options[:total_entries] : options[:total]
  end

  def total_pages
    (total.to_f / limit.to_f).ceil
  end

  def current_page
    (offset / limit) + 1
  end

  def max_pages
    (total / limit)
  end

  def next?
    current_page < max_pages
  end

  def previous?
    current_page > 0
  end

  def first
    Pagination.new({
      limit: limit,
      offset: 0,
      total: total
    })
  end

  def next
    return nil unless next?
    Pagination.new({
      limit: limit,
      offset: limit + offset,
      total: total
    })
  end

  def previous
    return nil unless previous?
    Pagination.new({
      limit: limit,
      offset: offset - limit,
      total: total
    })
  end

  def last
    Pagination.new({
      limit: limit,
      offset: max_pages - 1,
      total: total
    })
  end

  def to_hash
    {
      limit: limit,
      offset: offset,
      total: total
    }
  end

  def to_will_paginate_params
    {
      page: current_page,
      per_page: limit
    }
  end

  def to_json(*)
    JSON.dump(to_hash)
  end
end

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