canvas-lms/lib/custom_validations.rb

#
# Copyright (C) 2011 Instructure, Inc.
#
# This file is part of Canvas.
#
# Canvas is free software: you can redistribute it and/or modify it under
# the terms of the GNU Affero General Public License as published by the Free
# Software Foundation, version 3 of the License.
#
# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
# details.
#
# You should have received a copy of the GNU Affero General Public License along
# with this program. If not, see <http://www.gnu.org/licenses/>.
#

module CustomValidations
  class RelativeUriError < ArgumentError; end

  # returns [normalized_url_string, URI] if valid, raises otherwise
  def self.validate_url(value)
    value = value.strip
    raise ArgumentError if value.empty?
    uri = URI.parse(value)
    unless uri.scheme
      value = "http://#{value}"
      uri = URI.parse(value)
    end
    raise(RelativeUriError) if uri.host.blank?
    raise ArgumentError unless %w(http https).include?(uri.scheme.downcase)
    return value, uri
  end

  module ClassMethods

    def validates_as_url(*fields)
      validates_each(fields, :allow_nil => true) do |record, attr, value|
        begin
          value, uri = CustomValidations.validate_url(value)
          record.send("#{attr}=", value)
        rescue URI::InvalidURIError, ArgumentError
          record.errors.add attr, 'is not a valid URL'
        end
      end
    end

    def validates_as_readonly(*fields)
      validates_each(fields) do |record, attr, value|
        if !record.new_record? && record.send("#{attr}_changed?")
          record.errors.add attr, "cannot be changed"
        end
      end
    end

    # alloweds is a hash of old_value => [new_value]
    # on update, only those transitions will be allowed for the given field
    def validates_allowed_transitions(field, alloweds)
      validates_each(field) do |record, attr, value|
        if !record.new_record? && record.send("#{attr}_changed?")
          old_val = record.send("#{attr}_was")
          unless alloweds.any? { |old,news| old_val == old && Array(news).include?(value) }
            record.errors.add attr, "cannot be changed to that value"
          end
        end
      end
    end
  end

  def self.included(klass)
    if klass < ActiveRecord::Base
      klass.send :extend, ClassMethods
    end
  end

end