module Pjax
  class Error < StandardError; end
  class Unsupported < Error; end

  extend ActiveSupport::Concern

  included do
    layout proc { |c| pjax_request? ? pjax_layout : nil }
    helper_method :pjax_request?

    rescue_from Pjax::Unsupported, :with => :pjax_unsupported

    if respond_to? :before_action
      before_action :strip_pjax_param, :if => :pjax_request?
      before_action :set_pjax_url,     :if => :pjax_request?
    else
      before_filter :strip_pjax_param, :if => :pjax_request?
      before_filter :set_pjax_url,     :if => :pjax_request?
    end
  end

  protected

  def pjax_request?
    request.env['HTTP_X_PJAX'].present?
  end

  def pjax_layout
    false
  end

  def pjax_container
    return unless pjax_request?
    request.headers['X-PJAX-Container']
  end

  def pjax_unsupported
    head :not_acceptable
  end

  # Call in a before_action or in an action to disable pjax on an action.
  #
  # Examples
  #
  #     before_action :prevent_pjax!
  #
  #     def login
  #       prevent_pjax!
  #       # ...
  #     end
  #
  def prevent_pjax!
    raise Pjax::Unsupported if pjax_request?
  end

  def strip_pjax_param
    params.delete(:_pjax)
    request.env['QUERY_STRING'] = request.env['QUERY_STRING'].sub(/\A_pjax=[^&]+&?|&_pjax=[^&]+/, '')

    request.env.delete('rack.request.query_string')
    request.env.delete('rack.request.query_hash')
    request.env.delete('action_dispatch.request.query_parameters')

    request.instance_variable_set('@original_fullpath', nil)
    request.instance_variable_set('@fullpath', nil)
  end

  def set_pjax_url
    response.headers['X-PJAX-URL'] = request.url
  end
end