Super simple policy authentication.

authorization.gemspec

Gem::Specification.new do |s|
  s.name        = 'policy-authorization'
  s.version     = '0.0.2'
  s.platform    = Gem::Platform::RUBY
  s.author      = 'Kevin Melchert'
  s.email       = 'kevin.melchert@gmail.com'
  s.summary     = 'Super simple policy authentication.'
  s.description = 'Super simple policy authentication.'
 
  s.files         = ['authorization.rb']
  s.test_file     = 'authorization_helper_spec.rb'
  s.require_path  = '.'
end

authorization.rb

module Authorization
  Error  = Class.new(StandardError)
  Policy = Struct.new(:resource, :user)

  module Helpers
    private
    
    def authorize!(user, action, resource)
      raise Authorization::Error unless can?(user, action, resource)
    end

    def can?(user, action, resource)
      policy(resource, user).public_send :"#{action}?"
    end
    
    def policy(resource, user)
      Object.const_get("#{resource.class}Policy").new(resource, user)
    end
  end
end

authorization_helper_spec.rb

# -*- encoding: utf-8 -*-
require 'rubygems'
require 'bundler/setup'
require 'minitest/autorun'
require 'minitest/spec'
require 'authorization'

User = Struct.new(:name)
Post = Struct.new(:user)

PostPolicy = Struct.new(:post, :user) do
  def view? true; end
  def delete? false; end
  def own?
    post.user == user
  end
end

describe Authorization::Helpers do
  before do
    @user = User.new('Mr. Fox')
    @post = Post.new(@user)
  end
  
  include Authorization::Helpers
  
  describe 'can?' do
    it 'should return true if user can access a resource' do
      can?(@user, :view, @post).must_equal true
    end
    
    it 'should return false if user cannot access a resource' do
      can?(@user, :delete, @post).must_equal false
    end
  end
 
  describe 'authorize!' do
    it 'should do nothing if user can access a resource' do
      authorize!(@user, :view, @post).must_equal nil
    end
    
    it 'should raise error if user cannot access a resource' do
      proc { authorize!(@user, :delete, @post) }.must_raise Authorization::Error
    end
  end
  
  describe 'policy' do
    it 'should return the policy instance' do
      policy(@post, @user).must_be_instance_of PostPolicy
    end
  end
end