#!/usr/bin/python2.5

#

# Copyright 2008 the Melange authors.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

#   http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

"""Helpers used to display various views that are forms.

"""

__authors__ = [

  '"Chen Lunpeng" <forever.clp@gmail.com>',

  '"Todd Larsen" <tlarsen@google.com>',

  ]

from google.appengine.ext.db import djangoforms

from django.utils import safestring

class DbModelForm(djangoforms.ModelForm):

  """Subclass of Django ModelForm that fixes some label and help_text issues.

  The default behavior of ModelForm is to use the verbose_name in all

  lowercase, capitalizing only the first character, as the displayed field

  label.  This class uses verbose_name unaltered as the visible field label

  instead.

  The Property classes used by the App Engine Datastore do not have a

  help_text parameter to their constructor.  In a Model class, a help_text

  attribute *can* be added to the property after it is created, but the

  help text will not be automatically passed along to the Django ModelForm.

  This class detects the presence of a help_text attribute and adds it to

  the corresponding form field object.

  ugettext_lazy() proxies used for internationalization in the Model will

  still work correctly with this new behavior, as long as the original

  strings are used as the translation keys.

  """

  def __init__(self, *args, **kwargs):

    """Fixes label and help_text issues after parent initialization.

    Args:

      *args, **kwargs:  passed through to parent __init__() constructor

    """

    super(DbModelForm, self).__init__(*args, **kwargs)

    for field_name in self.fields.iterkeys():

      # Since fields can be added only to the ModelForm subclass, check to

      # see if the Model has a corresponding field first.

      if hasattr(self.Meta.model, field_name):

        model_prop = getattr(self.Meta.model, field_name)

        # Check if the Model property defined verbose_name, and copy that

        # verbatim to the corresponding field label.

        if hasattr(model_prop, 'verbose_name'):

          self.fields[field_name].label = model_prop.verbose_name

        # Check if the Model property added help_text, and copy that verbatim

        # to the corresponding field help_text.

        if hasattr(model_prop, 'help_text'):

          self.fields[field_name].help_text = model_prop.help_text

class SelectQueryArgForm(forms.Form):

  """URL query argument change control implemented as a Django form.

  """

  ONCHANGE_JAVASCRIPT_FMT = '''

<script type="text/javascript"> 

  function changeArg_%(arg_name)s(item) 

  {

    var idx=item.selectedIndex;

    item.selected=true;

    var value=item.value 

    var url = location.href 

    var reg = /%(arg_name)s=\d+/ 

    url = url.replace(reg, "%(arg_name)s="+value) 

    if(url.match(reg))

      document.location.href = url 

   else

      document.location.href = "%(page_path)s?%(arg_name)s="+value; 

  }

</script>

'''

  def __init__(self, page_path, arg_name, choices, field_name,

               *form_args, **form_kwargs):

    """

    Args:

      page_path: (usually request.path)

      arg_name: the URL query parameter that determines which choice is

        selected in the selection control

      choices: list (or tuple) of value/label string two-tuples, for example:

        (('10', '10 items per page'), ('25', '25 items per page'))

      field_name: name of the selection field in the form

      *form_args: positional arguments passed on to the Form base

        class __init__()

      *form_kwargs: keyword arguments passed on to the Form base

        class __init__()

    """

    super(SelectQueryArgForm, self).__init__(*form_args, **form_kwargs)

    self._script = safestring.mark_safe(self.ONCHANGE_JAVASCRIPT_FMT % {

        'arg_name': arg_name, 'page_path': page_path,})

    onchange_js_call = 'changeArg_%s(this)' % arg_name

    self.fields[field_name] = forms.ChoiceField(

        label='', choices=choices,

        widget=forms.widgets.Select(attrs={'onchange': onchange_js_call}))

  def as_table(self):

    """Returns form rendered as HTML <tr> rows -- with no <table></table>.

    Prepends <script> section with onchange function included.

    """

    return self._script + super(SelectQueryArgForm, self).as_table()

  def as_ul(self):

    """Returns form rendered as HTML <li> list items -- with no <ul></ul>.

    Prepends <script> section with onchange function included.

    """

    return self._script + super(SelectQueryArgForm, self).as_ul()

  def as_p(self):

    """Returns form rendered as HTML <p> paragraphs.

    Prepends <script> section with onchange function included.

    """

    return self._script + super(SelectQueryArgForm, self).as_p()

DEF_SELECT_QUERY_ARG_FIELD_NAME_FMT = 'select_query_arg_%(arg_name)s'

def makeSelectQueryArgForm(

    request, arg_name, initial_value, choices,

    field_name_fmt=DEF_SELECT_QUERY_ARG_FIELD_NAME_FMT):

  """Wrapper that creates a customized SelectQueryArgForm.

  Args:

    request: the standard Django HTTP request object

    arg_name: the URL query parameter that determines which choice is

      selected in the selection control

    initial_value: the initial value of the selection control

    choices: list (or tuple) of value/label string two-tuples, for example:

      (('10', '10 items per page'), ('25', '25 items per page'))

    field_name_fmt: optional form field name format string; default is

      DEF_SELECT_QUERY_ARG_FIELD_NAME_FMT; contains these named format

      specifiers:

        arg_name: replaced with the arg_name argument

  Returns:

    a Django form implementing a query argument selection control, for

    insertion into a template

  """

  field_name = field_name_fmt % {'arg_name': arg_name}

  return SelectQueryArgForm(request.path, arg_name, choices, field_name,

                            initial={field_name: initial_value})