utilities.rb

module Utilities
  def self.serializable attributes, serializable
    attributes.keep_if { |f, _| serializable.include? f }
    attributes.delete_if { |_, v| v.nil? }
    attributes
  end

  def self.is_url?(name)
    require 'uri'
    uri = URI.parse(name)
    return false if uri.nil? || uri.scheme.nil? || uri.scheme.empty?
    return true
  rescue URI::InvalidURIError
    return false
  end

  def self.execute_instructor_code(invoked_method_name)
    yield
  rescue Exception => e
    raise InstructorException.new("Error executing #{invoked_method_name}: #{e}")
  end 

  def self.validated_score_value(score, invoked_method_name, allow_nil = false)
    message = "Error executing #{invoked_method_name}"

    if score
      if (score = Float(score) rescue nil)
        raise InvalidComputedScoreException.new("#{message}: returned infinite number") unless score.finite?
      else
        raise InvalidComputedScoreException.new("#{message}: error converting to float")
      end
    else
      raise InvalidComputedScoreException.new("#{message}: returned nil") unless allow_nil
    end

    score
  end
end

class ScoreComputationException < StandardError 
end

class InvalidComputedScoreException < ScoreComputationException
end

class InstructorException < ScoreComputationException
end