Introduction
============

The ``horae.autocomplete`` package provides autocomplete fields and widgets for
`zope.formlib <http://pypi.python.org/pypi/zope.formlib>`_ based on the
`autocomplete widget of jQuery UI <http://jqueryui.com/demos/autocomplete>`_.

Usage
=====

There are two types of autocomplete fields available:

**AutocompleteList**
  Allows selection of multiple values
**AutocompleteChoice**
  Allows selection of one value

To enable autocompletion for a list or choice field simply replace the ``List``
respectively the ``Choice`` from `zope.schema <http://pypi.python.org/pypi/zope.schema>`_
by the one provided in ``horae.autocomplete.fields``::

    from zope import interface, schema
    
    from horae.autocomplete import fields
    
    class ISampleSchema(interface.Interface):
        """ A schema using an autocomplete choice and list field
        """
        
        choice = fields.AutocompleteChoice(
            values = (u'one', u'two', u'three',)
        )
        
        list = fields.AutocompleteList(
            value_type = schema.Choice(
                values=(u'Tag 1', u'Tag 2', u'Tag 3',)
            )
        )

The ``AutocompleteChoice`` field takes exactly the same parameters as the ``Choice`` field
provided by `zope.schema <http://pypi.python.org/pypi/zope.schema>`_. The same is true for
the ``AutocompleteList`` field which takes the same parameters as the ``List`` field of
`zope.schema <http://pypi.python.org/pypi/zope.schema>`_ with the only restriction that
the ``value_type`` has to be either a ``Choice`` or ``TextLine`` field.

Advanced usage
--------------

Value providers
'''''''''''''''

The available values presented to the user when entering a term into the field are provided
by adapters implementing ``horae.autocomplete.interfaces.IValueProvider``. There are default
value providers already implemented which look up the available values based on the given
input in the vocabulary of the field. This is done by iterating over the values in the
vocabulary and check whether a value matches the given input. For very large or infinite
vocabularies this is quite expensive or not possible at all. To efficiently support such
vocabularies value providers may be overridden by registering a more specific adapter
implementing ``horae.autocomplete.interfaces.IValueProvider``. Those adapters are looked
up in the following order where the first one found is used:

**Named contextual provider**
  A value provider adapting the ``context``, ``field`` and ``request`` registered with the
  same name as the field
**Named uncontextual provider**
  A value provider adapting the ``field`` and ``request`` registered with the same name as
  the field
**Contextual provider**
  A value provider adapting the ``context``, ``field`` and ``request``
**Uncontextual provider**
  A value provider adapting the ``field`` and ``request``

Examples of custom value providers is found in the `horae.search <http://pypi.python.org/pypi/horae.search>`_
package which provides non iterable vocabularies and corresponding value providers which
use full text search in a catalog to look up the available values based on the input.

Field providers
'''''''''''''''

As mentioned in the previous chapter the value providers are adapters adapting at least the
``field`` and the ``request``. To look up those providers the field needs to be looked up
first. In most cases this is not an issue at all since the fields are defined by the schema
of the form. But in some cases the field is placed in the form only when rendering it which
would then require to render the whole form only to find the required field. To efficiently
support this use-case the way how a field is looked up may be overridden by registering an
adapter implementing ``horae.autocomplete.interfaces.IFieldProvider`` and adapting the
``context`` and ``request``.

Dependencies
============

* `fanstatic <http://pypi.python.org/pypi/fanstatic>`_
* `zope.fanstatic <http://pypi.python.org/pypi/zope.fanstatic>`_
* `js.jquery <http://pypi.python.org/pypi/js.jquery>`_
* `js.jqueryui <http://pypi.python.org/pypi/js.jqueryui>`_
