Login with username or email using Rails 3

Please help me to login with username or email using Rails 3.I have two model i.e-Admin and User.Admin can only login through email id and user can only login through username.I need both login process.Please check my below codes and help me to resolve this issue.

views/admins/index.html.erb

<div id="login">
  <div id="triangle"></div>
  <h1>Log in</h1>
  <%= form_for :admin,:url => {:action => "login" ,:controller => "sessions" } do |f| %>
  <%= f.text_field :login,placeholder:"Enter your email or username" %>
  <%= f.password_field :password,placeholder:"Enter your password" %>
  <%= f.submit "Log in" %>
  <% end %>
  <% if @admin.try(:errors).try(:any?) %>
    <div id="error_explanation">
    <h2><%= pluralize(@admin.errors.count, "error") %> prohibited this post from being saved:</h2>

    <ul>
    <% @admin.errors.full_messages.each do |msg| %>
   <li><%= msg %></li>
   <% end %>
   </ul>
  </div>
<% end %>
</div>

sessions/sessions_contrtoller.rb

class SessionsController < ApplicationController
    def login
        @admin=Admin.authenticate(params[:admin][:email], params[:admin][:password])
        if @admin
            session[:user_id]=@admin.id
            cookies.signed[:user_id]=@admin.id
            flash[:notice]="Login Successfull"
            flash[:color]="valid"
            redirect_to :action => 'index', :controller => "homes"
        else
            flash[:notice]="Login failed"
            flash[:color]="invalid"
            render 'admins/index'
        end
    end
    def removeadmin
        session[:user_id] = nil
        cookies.delete :user_id
        flash[:notice]="user logged out successfully"
        flash[:color]="valid"
        redirect_to :action => 'index', :controller => 'admins'
    end
end

model/admin.rb

class Admin < ActiveRecord::Base
  attr_accessible :email, :name, :password, :phoneno
  attr_accessor :login
  EMAIL_REGEX = /\A[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\z/i
 validates :email, :presence => true, :uniqueness => true, :format => EMAIL_REGEX
 validates_length_of :password, :in => 6..20, :on => :create
 has_many :user
 def self.authenticate(email, password)
    admin = find_by_email(email)
    if admin && admin.password==password
      admin
    else
      nil
    end
  end
end

model/user.rb

class User < ActiveRecord::Base
  belongs_to :admin
  attr_accessible :email, :password_hash, :password_salt, :phoneno, :user_name,:password, :password_confirmation
  attr_accessor :password
  before_save :encrypt_password
  validates_confirmation_of :password
  validates_presence_of :password, :on => :create
  validates_presence_of :email
  validates_uniqueness_of :email
  def encrypt_password
    if password.present?
      self.password_salt = BCrypt::Engine.generate_salt
      self.password_hash = BCrypt::Engine.hash_secret(password, password_salt)
    end
  end
end

As i am new to RoR. Please help me to resolve this issue.