# Tom Moertel <tom@moertel.com>
  # 2005-05-08

  # Generates a form containing a sole button that submits to the URL
  # given by _options_.  Use this method instead of +link_to+ for
  # dangerous actions that do not have the safe HTTP GET semantics
  # implied by using a hypertext link.
  #
  # The parameters are the same as for +link_to+.  Any _html_options_
  # that you pass will be applied to the inner +input+ element.  The
  # generated form element is given the class 'button-to', to which
  # you can attach CSS styles for display purposes.
  #
  # Example 1:
  #
  #   # inside of controller 'feeds'
  #   button_to "Edit", :action => 'edit', :id => 3
  #
  # Generates the following HTML (sans formatting):
  #
  #   <form method="post" action="/feeds/edit/3" class="button-to">
  #     <div><input value="Edit" type="submit"></div>
  #   </form>
  #
  # Example 2:
  #
  #   button_to "Destroy", { :action => 'destroy', :id => 3 },
  #             :confirm => "Are you sure?"
  #
  # Generates the following HTML (sans formatting):
  #
  #   <form method="post" action="/feeds/destroy/3" class="button-to">
  #     <div><input onclick="return confirm('Are you sure?');"
  #                 value="Destroy" type="submit">
  #     </div>
  #   </form>
  #
  # *NOTE*: This method generates HTML code that represents a form.
  # Forms are "block" content, which means that you should not try to
  # insert them into your HTML where only inline content is expected.
  # For example, you can legally insert a form inside of a +div+ or
  # +td+ element or in between +p+ elements, but not in the middle of
  # a run of text, nor can you place a form within another form.
  # (Bottom line: Always validate your HTML before going public,
  # especially if this paragraph seems confusing.)

  def button_to(name, options = {}, html_options = nil)
    html_options = (html_options || {}).stringify_keys
    convert_boolean_attributes! html_options, %w( disabled )
    convert_confirm_option_to_javascript! html_options
    url, name = options.is_a?(String) ? 
      [ options,  name || options ] :
      [ url_for(options), name || url_for(options) ]
    html_options.merge!("type" => "submit", "value" => name)
    "<form method='post' action='#{h url}' class='button-to'><div>" +
      tag("input", html_options) + "</div></form>"
  end


  # Processes the _html_options_ hash, converting the boolean
  # attributes from true/false form into the form required by
  # HTML/XHTML.  (An attribute is considered to be boolean if it is
  # listed in the given _bool_attrs_ array.)
  #
  # More specifically, for each boolean attribute in _html_options_
  # given as:
  #
  #     "attr" => bool_value
  #
  # if the the associated _bool_value_ evaluates to true, it is
  # replaced with the attribute's name; otherwise the attribute is
  # removed from the _html_options_ hash.  (See the XHTML 1.0 spec,
  # section 4.5 "Attribute Minimization" for more:
  # http://www.w3.org/TR/xhtml1/#h-4.5)
  #
  # Returns the updated _html_options_ hash, which is also modified
  # in place.
  #
  # Example:
  #
  #   convert_boolean_attributes!( html_options,
  #                                %w( checked disabled readonly ) )

  def convert_boolean_attributes!(html_options, bool_attrs)
    bool_attrs.each { |x| html_options[x] = x if html_options.delete(x) }
    html_options
  end