<!-- This tag, when given a list, chunks the list using the [jQuery-UI accordion](jqueryui.com/demos/accordion).

If you do not specify the `chunker` attribute, the list is chunked into sections of equal length.   The default is 20 items, but that may be adjusted by setting the `per-section` attribute.

The `chunker` may be passed a block to specify custom chunking.   This block is passed to [Enumerable#chunk](http://www.ruby-doc.org/core-1.9.3/Enumerable.html#method-i-chunk)  For example, to divide a sorted list of users based on the first letter of their name:

    <accordion-collection:users chunker="&Proc.new{|u| u.name[0..1]}"/>

The scoped variable `chunk` is set to the chunker output.   If you didn't specify the chunker, it's set to the chunk number.   In the example above, it would be set to the first letter of the user's name.   Here's an example of it being used to customize the chunk heading:

    <heading:>Section <%= scope.chunk %></heading:>

The context is set to the chunked list for all parameters.   This allows us to further customize the heading:

    <header:><name:first/> &mdash; <name:last/></header:>

Replacing the collection with a table is easy:

    <default:><table fields="this,email"/></default:>

Remember that the default parameter is a list, even if you set per-section="1".   The easiest way to explode a list is with `<repeat>`:

    <accordion-collection per-section="1">
      <header:><name:first/></header:>
      <default:>
        <repeat>
          This is my content: <view/>
        </repeat>
      </default:>
    </accordion-collection>


### Note:

This tag uses Enumerable#chunk, which is only available with Ruby 1.9.2 and later.   If you are using Ruby 1.8.7, you must include the `backports` gem in your project.

### Attributes:

- `per-section`, `chunker`:  (see above).   Only one of these should
  be used.   Using neither results is the same as saying
  per-section="20"

- `sortable`: if set, the accordion is sortable, although the sort
  order is not saved.

-->
<def tag="accordion-collection" attrs="per-section,chunker,sortable">
  <% options, attrs = attributes.partition_hash(['disabled', 'active', 'animated', 'autoHeight', 'clearStyle', 'collapsible', 'event', 'fillSpace', 'header', 'icons', 'navigation'])
     events, html_attrs = attrs.partition_hash(['navigationFilter', 'create', 'change', 'changestart'])
     add_classes!(html_attrs, "accordion-collection")
     add_data_rapid!(html_attrs, "accordion", :options => options, :events => events, :sortable => sortable)
     %>
  <div merge-attrs="&html_attrs">
  <% per_section ||= 20 %>
  <% per_section = per_section.to_i %>
  <% counter = 0 %>
  <% chunker ||= Proc.new{|el| counter=counter+1; (counter-1)/per_section+1} %>
  <repeat with="&this.to_a.chunk(&chunker)">
    <% chunk, list = this %>
    <% list.member_class = this.member_class if this._?.member_class%>
    <set-scoped chunk="&chunk">
      <do with="&list">
        <div class="hjq-accordion-element">
          <h3 param="header-wrapper">
            <a param="header" href="#"><%= scope.chunk %></a>
          </h3>
          <div param="default">
            <collection without-empty-message param/>
          </div>
        </div>
      </do>
    </set-scoped>
  </repeat>
  </div>
</def>