require 'action_view/helpers/tag_helper'

module ActionView
  # = Action View JavaScript Helpers
  module Helpers
    # Provides functionality for working with JavaScript in your views.
    #
    # == Ajax, controls and visual effects
    #
    # * For information on using Ajax, see
    #   ActionView::Helpers::PrototypeHelper.
    # * For information on using controls and visual effects, see
    #   ActionView::Helpers::ScriptaculousHelper.
    #
    # == Including the JavaScript libraries into your pages
    #
    # Rails includes the Prototype JavaScript framework and the Scriptaculous
    # JavaScript controls and visual effects library.  If you wish to use
    # these libraries and their helpers (ActionView::Helpers::PrototypeHelper
    # and ActionView::Helpers::ScriptaculousHelper), you must do one of the
    # following:
    #
    # * Use <tt><%= javascript_include_tag :defaults %></tt> in the HEAD
    #   section of your page (recommended): This function will return
    #   references to the JavaScript files created by the +rails+ command in
    #   your <tt>public/javascripts</tt> directory. Using it is recommended as
    #   the browser can then cache the libraries instead of fetching all the
    #   functions anew on every request.
    # * Use <tt><%= javascript_include_tag 'prototype' %></tt>: As above, but
    #   will only include the Prototype core library, which means you are able
    #   to use all basic AJAX functionality. For the Scriptaculous-based
    #   JavaScript helpers, like visual effects, autocompletion, drag and drop
    #   and so on, you should use the method described above.
    #
    # For documentation on +javascript_include_tag+ see
    # ActionView::Helpers::AssetTagHelper.
    module JavaScriptHelper
      include PrototypeHelper

      JS_ESCAPE_MAP = {
        '\\'    => '\\\\',
        '</'    => '<\/',
        "\r\n"  => '\n',
        "\n"    => '\n',
        "\r"    => '\n',
        '"'     => '\\"',
        "'"     => "\\'" }

      # Escape carrier returns and single and double quotes for JavaScript segments.
      # Also available through the alias j(). This is particularly helpful in JavaScript responses, like:
      #
      #   $('some_element').replaceWith('<%=j render 'some/element_template' %>');
      def escape_javascript(javascript)
        if javascript
          javascript.gsub(/(\\|<\/|\r\n|[\n\r"'])/) { JS_ESCAPE_MAP[$1] }
        else
          ''
        end
      end

      alias_method :j, :escape_javascript

      # Returns a JavaScript tag with the +content+ inside. Example:
      #   javascript_tag "alert('All is good')"
      #
      # Returns:
      #   <script type="text/javascript">
      #   //<![CDATA[
      #   alert('All is good')
      #   //]]>
      #   </script>
      #
      # +html_options+ may be a hash of attributes for the <tt>\<script></tt>
      # tag. Example:
      #   javascript_tag "alert('All is good')", :defer => 'defer'
      #   # => <script defer="defer" type="text/javascript">alert('All is good')</script>
      #
      # Instead of passing the content as an argument, you can also use a block
      # in which case, you pass your +html_options+ as the first parameter.
      #   <%= javascript_tag :defer => 'defer' do -%>
      #     alert('All is good')
      #   <% end -%>
      def javascript_tag(content_or_options_with_block = nil, html_options = {}, &block)
        content =
          if block_given?
            html_options = content_or_options_with_block if content_or_options_with_block.is_a?(Hash)
            capture(&block)
          else
            content_or_options_with_block
          end

        content_tag(:script, javascript_cdata_section(content), html_options.merge(:type => Mime::JS))
      end

      def javascript_cdata_section(content) #:nodoc:
        "\n//#{cdata_section("\n#{content}\n//")}\n".html_safe
      end

      # Returns a button whose +onclick+ handler triggers the passed JavaScript.
      #
      # The helper receives a name, JavaScript code, and an optional hash of HTML options. The
      # name is used as button label and the JavaScript code goes into its +onclick+ attribute.
      # If +html_options+ has an <tt>:onclick</tt>, that one is put before +function+.
      #
      #   button_to_function "Greeting", "alert('Hello world!')", :class => "ok"
      #   # => <input class="ok" onclick="alert('Hello world!');" type="button" value="Greeting" />
      #
      def button_to_function(name, function='', html_options={})
        onclick = "#{"#{html_options[:onclick]}; " if html_options[:onclick]}#{function};"

        tag(:input, html_options.merge(:type => 'button', :value => name, :onclick => onclick))
      end

      # Returns a link whose +onclick+ handler triggers the passed JavaScript.
      #
      # The helper receives a name, JavaScript code, and an optional hash of HTML options. The
      # name is used as the link text and the JavaScript code goes into the +onclick+ attribute.
      # If +html_options+ has an <tt>:onclick</tt>, that one is put before +function+. Once all
      # the JavaScript is set, the helper appends "; return false;".
      #
      # The +href+ attribute of the tag is set to "#" unles +html_options+ has one.
      #
      #   link_to_function "Greeting", "alert('Hello world!')", :class => "nav_link"
      #     Produces:
      #       <a onclick="alert('Hello world!'); return false;" href="#" class="nav_link">Greeting</a>
      def link_to_function(name, function, html_options={})
        onclick = "#{"#{html_options[:onclick]}; " if html_options[:onclick]}#{function}; return false;"
        href = html_options[:href] || '#'

        content_tag(:a, name, html_options.merge(:href => href, :onclick => onclick))
      end
    end
  end
end