_invoice.html.erb

...
  <td class="Text13Grey numeric">
    <span id="invoice_paid_status_<%= invoice.url_id %>"> <%= partial_payment_in_redbox(invoice) %></span>
  </td>
...

_partial_payment.html.erb

<div id="redbox-for-partial-payment-<%=invoice.id%>" class="redbox_contents" style="display: none; width: 300px;">
  <% remote_form_for PartialPayment.new, :url => invoice_partial_payments_path(invoice, :locale => "es") do |f| %>
    <div id="total_payment_<%=invoice.id%>" class="box">
        <p class="Text13Grey text"><%= t('.choose_payment') %></p>
        <div class="buttonbar">
            <%= button_to_function t('.full_payment'), :class=> "button", :id => "full-payment", :onclick => "fullPayment(#{invoice.id});"%>
            <%= button_to_function t('.partial_payment'), :class=> "button", :id => "partial-payment", :onclick => "partialPayment(#{invoice.id});" %>
        </div>
    </div>
    <div id="partial_payment_form_<%=invoice.id%>" class="box" style="display: none;">
      <label class="Text13Grey text"><%= t('.amount_message') %><%= f.text_field :amount, :maxlength => 13, :size => 13, :class => "amount", :value => (invoice.total - invoice.total_paid)%></label>
      <div class="buttonbar">
        <%= button_to_function t ('.cancel'), "RedBox.close()", :class => 'button' %>
        <%= f.submit t('.accept'), :class => 'button' %>
      </div>
    </div>
  </div>
  <% end %>
</div>

invoice_helper.rb

...


  def partial_payment_in_redbox (invoice)
    pending = invoice.total-invoice.total_paid
    if pending > 0
      html = render(:partial => 'invoices/redbox/partial_payment', :object => invoice)
      html << link_to_redbox (format_money_as_decimal (pending), 'redbox-for-partial-payment', :class => "Text13Orange")
      html
    else
      html = format_money_as_decimal (0)
    end
  end

...

routes.rb

ActionController::Routing::Routes.draw do |map|
  map.filter 'locale'
  # The priority is based upon order of creation: first created -> highest priority.
  
  # Sample of regular route:
  # map.connect 'products/:id', :controller => 'catalog', :action => 'view'
  # Keep in mind you can assign values other than :controller and :action

  # Sample of named route:
  # map.purchase 'products/:id/purchase', :controller => 'catalog', :action => 'purchase'
  # This route can be invoked with purchase_url(:id => product.id)

  # You can have the root of your site routed by hooking up '' 
  # -- just remember to delete public/index.html.
  map.home_public '',    :controller => "public",   :action => 'index', :conditions => {:subdomain => 'www'}
  map.who         'who', :controller => "public",   :action => 'who',   :conditions => {:subdomain => 'www'}
  map.connect     '',    :controller => "invoices", :action => 'index'

  # A/B testing routes
  map.home1   'home1', :controller => 'public', :action => 'home1', :conditions => {:subdomain => 'www'}
  map.home2   'home2', :controller => 'public', :action => 'home2', :conditions => {:subdomain => 'www'}
  map.home3   'home3', :controller => 'public', :action => 'home3', :conditions => {:subdomain => 'www'}
  map.home4   'home4', :controller => 'public', :action => 'home4', :conditions => {:subdomain => 'www'}

  map.pymesyautonomos 'pymesyautonomos', :controller => "public", :action => 'pymesyautonomos'
  
  map.with_options :controller => 'apidocs' do |doc|
    doc.api           'api',          :action => 'index'
    doc.api_concepts  'api/concepts', :action => 'concepts'
    doc.api_routes    'api/routes',   :action => 'routes'
    doc.api_model     'api/:model',   :action => 'model'
  end

  map.namespace(:api_v1, :path_prefix => 'api/1') do |api|
    api.resource :account, :except => [:new, :create, :edit, :update, :destroy], :member => {:token => :get}
    api.resources :countries, :except => [:new, :create, :edit, :update, :destroy]
    api.resources :customers, :except => [:new, :edit], :collection => {:search => :get} do |customer|
      customer.resources :invoices, :except => [:new, :edit, :update],
                         :collection => {:search => :get, :pending => :get, :paid => :get}
    end
    api.resources :invoices, :except => [:new, :edit, :update],
                            :collection => {:search => :get, :pending => :get, :paid => :get},
                            :member => {:mail_to => :post, :toggle_paid => :post} do |invoice|
      invoice.resources :invoice_lines, :except => [:new, :edit]
    end
  end
  
  # These promotion URLs have this schema for historical reasosn
  map.connect 'public/signup/:promotion_code',  :controller => 'public', :action => 'promotion', :promotion_code => /\w+/
  map.account_login_token 'account/login/:login_token', :controller => 'login_token', :action => 'login', :requirements => {:login_token => /.+/}
  map.account_login 'account/login',    :controller => 'account',  :action => 'login'
  map.account_logout 'account/logout', :controller => 'account', :action => 'logout'
  map.resource 'password', :only => [:new, :create, :edit, :update]
  
  map.connect 'promotion/:promotion_code',     :controller => 'public', :action => 'promotion'
  map.connect 'facturagem/mo',                 :controller => 'mo',       :action => 'index'

  map.connect 'invoices/new/:from/:id',        :controller => 'invoices', :action => 'new'
  map.resources 'invoices', :only => [:index, :new], :collection => {:list => :get, :search => :get}, :member => {:deliver => :post}  do |invoice|
      invoice.resources :partial_payments, :only => [:create]
  end

  map.resources 'customers', :only => [:index, :new, :create, :show, :edit, :update], :collection => {:list => :get, :search => :get, :export => :get}
  map.resource 'fiscal_data', :controller => 'fdata',
                              :as => "fdata",
                              :only => [:show, :new, :create, :edit, :update],
                              :collection => { :edit_plan => :get, :update_plan => :put }
  map.resources 'drafts', :path_prefix => 'invoices'

  map.unassign_report_assignment 'report_assignments/:id/unassign',
                                 :controller => 'report_assignments', :action => 'unassign', :conditions => {:method => :get}

  map.change_format '/format/:f', :controller => 'public', :action => 'change_format'

  # Public paths
  map.new_contact_form '/public/contact', :controller => 'contact_form', :action => 'new', :conditions => {:method => :get}
  map.contact_form '/public/contact', :controller => 'contact_form', :action => 'create', :conditions => {:method => :post}
  map.help '/help', :controller => 'help', :action => 'index', :conditions => {:method => :get}
  map.videos '/help/videos', :controller => 'help', :action => 'videos', :conditions => {:method => :get}
  map.tour '/tour', :controller => 'tour', :action => 'index', :conditions => {:method => :get}
  map.signup '/public/signup', :controller => 'public', :action => 'signup', :conditions => {:method => :get}

  # Backoffice paths
  map.flat_rate_backoffice '/backoffice/flat_rate', :controller => :backoffice, :action => "flat_rate"
  map.yearly_plan_backoffice '/backoffice/yearly_plan', :controller => :backoffice, :action => "yearly_plan"
  map.resume_backoffice '/backoffice', :controller => :backoffice, :action => "index"
  map.namespace(:backoffice) do |backoffice|
    backoffice.resources :accounts, :only => [:index, :update], :collection => {:list => :get, :search => :get}  
    backoffice.resources :promotions, :collection => {:list => :get, :search => :get}
  end

  # Orders & Payments
  map.resources :orders, :collection => { :success => :get, :failure => :get},
                         :member => { :cancel => :get }
  map.resources :payments

  # Call center external requests paths
  map.connect 'externals/call_center_create_account', :controller => :externals, :action => :call_center_create_account, :conditions => {:method => :post}

  map.welcome 'welcome', :controller => "fdata", :action => 'welcome'

  map.connect ':controller/:action/:id'
  # Install the default route as the lowest priority.
  # map.connect ':controller/:action/:id.:format'
end