Improve FilteredSelectionForm

Improve the configuration process of the FilteredSelectionForm form
by adding Meta child class support. The child Meta class
is defined in FilteredSelectionFormOptions.

Signed-off-by: Roberto Rosario <Roberto.Rosario.Gonzalez@gmail.com>

mayan/apps/common/forms.py

@@ -4,10 +4,13 @@ import os
 
 from django import forms
 from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
 from django.db import models
 from django.utils.module_loading import import_string
 from django.utils.translation import ugettext_lazy as _
 
+from mayan.apps.acls.models import AccessControlList
+
 from .classes import Package
 from .models import UserLocaleProfile
 from .utils import resolve_attribute
@@ -111,7 +114,10 @@ class FileDisplayForm(forms.Form):
     text = forms.CharField(
         label='',
         widget=TextAreaDiv(
-            attrs={'class': 'full-height scrollable', 'data-height-difference': 270}
+            attrs={
+                'class': 'full-height scrollable',
+                'data-height-difference': 270
+            }
         )
     )
 
@@ -125,6 +131,102 @@ class FileDisplayForm(forms.Form):
                 self.fields['text'].initial = file_object.read()
 
 
+class FilteredSelectionFormOptions(object):
+    # Dictionary list of option names and default values
+    option_definitions = (
+        {'allow_multiple': False},
+        {'field_name': None},
+        {'help_text': None},
+        {'label': None},
+        {'model': None},
+        {'permission': None},
+        {'queryset': None},
+        {'user': None},
+        {'widget_class': None},
+        {'widget_attributes': {'size': '10'}},
+    )
+
+    def __init__(self, form, kwargs, options=None):
+        """
+        Option definitions will be iterated. The option value will be
+        determined in the following order: as passed via keyword
+        arguments during form intialization, as form get_... method or
+        finally as static Meta options. This is to allow a form with
+        Meta options or method to be overrided at initialization
+        and increase the usability of a single class.
+        """
+        for option_definition in self.option_definitions:
+            name = option_definition.keys()[0]
+            default_value = option_definition.values()[0]
+
+            try:
+                # Check for a runtime value via kwargs
+                value = kwargs.pop(name)
+            except KeyError:
+                try:
+                    # Check if there is a get_... method
+                    value = getattr(self, 'get_{}'.format(name))()
+                except AttributeError:
+                    try:
+                        # Check the meta class options
+                        value = getattr(options, name)
+                    except AttributeError:
+                        value = default_value
+
+            setattr(self, name, value)
+
+
+class FilteredSelectionForm(forms.Form):
+    """
+    Form to select the from a list of choice filtered by access. Can be
+    configure to allow single or multiple selection.
+    """
+    def __init__(self, *args, **kwargs):
+        opts = FilteredSelectionFormOptions(
+            form=self, kwargs=kwargs, options=getattr(self, 'Meta', None)
+        )
+
+        if opts.queryset is None:
+            if not opts.model:
+                raise ImproperlyConfigured(
+                    '{} requires a queryset or a model to be specified as '
+                    'a meta option or passed during initialization.'.format(
+                        self.__class__
+                    )
+                )
+
+            queryset = opts.model.objects.all()
+        else:
+            queryset = opts.queryset
+
+        if not opts.widget_class:
+            if opts.allow_multiple:
+                extra_kwargs = {}
+                field_class = forms.ModelMultipleChoiceField
+                widget_class = forms.widgets.SelectMultiple
+            else:
+                extra_kwargs = {'empty_label': None}
+                field_class = forms.ModelChoiceField
+                widget_class = forms.widgets.Select
+        else:
+            widget_class = opts.widget_class
+
+        super(FilteredSelectionForm, self).__init__(*args, **kwargs)
+
+        if opts.permission:
+            queryset = AccessControlList.objects.filter_by_access(
+                permission=opts.permission, queryset=queryset,
+                user=opts.user
+            )
+
+        self.fields[opts.field_name] = field_class(
+            help_text=opts.help_text, label=opts.label,
+            queryset=queryset, required=True,
+            widget=widget_class(attrs=opts.widget_attributes),
+            **extra_kwargs
+        )
+
+
 class LicenseForm(FileDisplayForm):
     DIRECTORY = ()
     FILENAME = 'LICENSE'