server.rb

require 'sinatra'
require 'haml'

$users = {'john' => {:roles => [:user] }, 'mike' => {:roles => [:user, :admin] } }
$tokens = {'123' => {:username => 'john', :expires_at => Time.now+60}}

helpers do
	def authenticate_user!
		@auth_token = auth_token
		if $tokens.has_key?(@auth_token) && !$tokens[@auth_token][:expires_at].nil? && $tokens[@auth_token][:expires_at] > Time.now
			@current_user = $tokens[@auth_token][:username]
		else
			@current_user = nil
		end
	end
	def current_user 
		@current_user
	end
	def login?
		!@current_user.nil?
	end
	def activate!(token)
		if $tokens.has_key?(token) && $tokens[token][:expires_at].nil?
			$tokens[token][:expires_at] = Time.now + 600
			return true
		end
	end
	def logout
		$tokens.delete(@auth_token) 
	end
	def roles?(roles)
		return true if roles.include?(:any)
		!(roles & $users[@current_user][:roles]).empty?
	end
	def auth_token
		if params.has_key?("auth_token")
			return params["auth_token"] 
		elsif request.env.has_key?('HTTP_AUTHENTICATION')
			return request.env["HTTP_AUTHENTICATION"][/Token token="?(\w+)"?/,1]
		end
	end
	def generate_auth_token
	    begin
	      token = SecureRandom.hex(20)
	    end while $tokens.has_key?(token)
	    token
  	end
end

set(:auth) do |*roles|
  condition do
  	halt 401, 'Unauthorized' unless login?
  	halt 403, 'Forbidden' unless roles?(roles.to_a)
  end
end

before do
	authenticate_user!
end

get '/' do
	haml :index
end

get "/resource", :auth => [:user, :admin] do
	"You can access the resource for authorized users"
end

get "/secret", :auth => [:admin] do
	"You can accesss the resource only for admins"
end

get "/login" do
	haml :login
end

get "/logout", :auth => [:any] do
	logout
	haml :logout
end

post "/login" do
	haml :not_authorized unless $users.include?(params[:email])

	@token = generate_auth_token
	$tokens[@token] = {:username => params[:email], :expires_at => nil}

	haml :authentication_email
end

get "/activate/:token" do
	@token = params[:token]
	if activate!(params[:token])
		haml :authenticated
	else
		haml :not_authenticated
	end
end

__END__

@@layout
!!! 5
%html
	%head
		%title Sinatra Instant Email Authentication
	%body
		=yield

@@index
:javascript

	fetch = function(url,id) {
		var xhr = new XMLHttpRequest();
		xhr.open('GET', url);
		xhr.setRequestHeader('Authentication', 'Token token=' + localStorage.getItem('auth_token') );
		xhr.onload = function(e) {
				document.getElementById(id).innerHTML = (this.status == 200) ? this.responseText : this.status + ' ' + this.statusText;
		};
		xhr.send();
	}
	logout = function() {
		window.location.href = "/logout?auth_token=" + localStorage.getItem('auth_token');
	}
	fetch('/resource', 'resource');
	fetch('/secret', 'secret');

%a(href="/login") Login
%a(href="#" onclick="logout();" ) Logout
%p 
	XHR Repsonse on authorized users: 
	%span#resource
%p
	XHR Response on a secret resource only for admin:
	%span#secret

@@login
%form(action="/login" method="post")
	%div
		%label(for="email")Enter your email:
		%input#email(type="text" name="email")
	%div
		%input(type="submit" value="Login") 

@@authentication_email
:javascript
	localStorage.setItem('auth_token', '#{@token}');
%p Here is your email for authenticating.
%p In order to login into the system, please follow this link:
%a(href="/activate/#{@token}") Log me in

@@logout
:javascript
	localStorage.removeItem('auth_token');
%p You have logged out
%a(href="/") Home

@@authenticated
%p 
	You have logged in and now you can access your 
	%a(href="/") home

@@not_authenticated
%p 
	You activation failed. 

@@not_authorized
%p You are not authorized.