class Seatsio::Pagination::Cursor

def each(start = 0, &block)
  return to_enum(:each, start) unless block_given?
  Array(@collection[start..-1]).each do |element|
    yield(element)
  end
  return unless keep_running?
  return if last?
  start = [@collection.size, start].max
  fetch_next_page
  each(start, &block)
end

def fetch_next_page
  response = @http_client.get(@endpoint, URI.encode_www_form(@params))
  if response.nil? || response['items'].empty?
    @last_response_empty = true
    return
  end
  @next_page_starts_after = response['next_page_starts_after'].to_i if response['next_page_starts_after']
  @previous_page_ends_before = response['previous_page_ends_before'].to_i if response['previous_page_ends_before']
  items = response['items']
  parsed_items = []
  items.each {|item| parsed_items << (@cls.respond_to?(:from_json) ? @cls.from_json(item) : @cls.new(item))}
  @collection += parsed_items
  set_query_param(:start_after_id, items.last['id']) unless last?
end

def first_page(limit = nil)
  @first_page = true
  set_query_param(:limit, limit) unless limit.nil?
  self
end

def initialize(cls, endpoint, http_client, params = {})
  @cls = cls
  @endpoint = endpoint
  @http_client = http_client
  @params = params
  @collection = []
  @next_page_starts_after = nil
  @previous_page_ends_before = nil
  @first_page = false
end

def keep_running?
  return false if @first_page && !@collection.empty?
  return false if !params[:limit].nil? && !@collection.empty?
  return false if @params.include?(:end_before_id) && !@collection.empty?
  true
end

def last?
  return true if @last_response_empty
  false if @next_page_starts_after.is_a? Integer
end

def page_after(after_id = nil, limit = nil)
  set_query_param(:start_after_id, after_id) unless after_id.nil?
  set_query_param(:limit, limit) unless limit.nil?
  self
end

def page_before(before_id = nil, limit = nil)
  set_query_param(:end_before_id, before_id) unless before_id.nil?
  set_query_param(:limit, limit) unless limit.nil?
  self
end

def set_query_param(key, value)
  @params[key] = value
end