#
#    Autocomplete feature for admin panel
#
#    Most of the code has been written by Jannis Leidel and was updated a bit
#    for django_extensions.
#    http://jannisleidel.com/2008/11/autocomplete-form-widget-foreignkey-model-fields/
#
#    to_string_function, Satchmo adaptation and some comments added by emes
#    (Michal Salaban)
#
import operator
from django.http import HttpResponse, HttpResponseNotFound
from django.contrib import admin
from django.db import models
from django.db.models.query import QuerySet
from django.utils.encoding import smart_str
from django.utils.translation import ugettext as _
from django.utils.text import get_text_list

from django_extensions.admin.widgets import ForeignKeySearchInput

class ForeignKeyAutocompleteAdmin(admin.ModelAdmin):
    """Admin class for models using the autocomplete feature.

    There are two additional fields:
       - related_search_fields: defines fields of managed model that
         have to be represented by autocomplete input, together with
         a list of target model fields that are searched for
         input string, e.g.:
         
         related_search_fields = {
            'author': ('first_name', 'email'),
         }

       - related_string_functions: contains optional functions which
         take target model instance as only argument and return string
         representation. By default __unicode__() method of target
         object is used.
    """

    related_search_fields = {}
    related_string_functions = {}

    def __call__(self, request, url):
        if url is None:
            pass
        elif url == 'foreignkey_autocomplete':
            return self.foreignkey_autocomplete(request)
        return super(ForeignKeyAutocompleteAdmin, self).__call__(request, url)

    def foreignkey_autocomplete(self, request):
        """
        Searches in the fields of the given related model and returns the 
        result as a simple string to be used by the jQuery Autocomplete plugin
        """
        query = request.GET.get('q', None)
        app_label = request.GET.get('app_label', None)
        model_name = request.GET.get('model_name', None)
        search_fields = request.GET.get('search_fields', None)
        object_pk = request.GET.get('object_pk', None)
        try:
            to_string_function = self.related_string_functions[model_name]
        except KeyError:
            to_string_function = lambda x: x.__unicode__()
        if search_fields and app_label and model_name and (query or object_pk):
            def construct_search(field_name):
                # use different lookup methods depending on the notation
                if field_name.startswith('^'):
                    return "%s__istartswith" % field_name[1:]
                elif field_name.startswith('='):
                    return "%s__iexact" % field_name[1:]
                elif field_name.startswith('@'):
                    return "%s__search" % field_name[1:]
                else:
                    return "%s__icontains" % field_name
            model = models.get_model(app_label, model_name)
            queryset = model._default_manager.all()
            data = ''
            if query:
                for bit in query.split():
                    or_queries = [models.Q(**{construct_search(
                        smart_str(field_name)): smart_str(bit)})
                            for field_name in search_fields.split(',')]
                    other_qs = QuerySet(model)
                    other_qs.dup_select_related(queryset)
                    other_qs = other_qs.filter(reduce(operator.or_, or_queries))
                    queryset = queryset & other_qs
                data = ''.join([u'%s|%s\n' % (
                    to_string_function(f), f.pk) for f in queryset])
            elif object_pk:
                try:
                    obj = queryset.get(pk=object_pk)
                except:
                    pass
                else:
                    data = to_string_function(obj)
            return HttpResponse(data)
        return HttpResponseNotFound()

    def get_help_text(self, field_name, model_name):
        searchable_fields = self.related_search_fields.get(field_name, None)
        if searchable_fields:
            help_kwargs = {
                'model_name': model_name,
                'field_list': get_text_list(searchable_fields, _('and')),
            }
            return _('Use the left field to do %(model_name)s lookups in the fields %(field_list)s.') % help_kwargs
        return ''

    def formfield_for_dbfield(self, db_field, **kwargs):
        """
        Overrides the default widget for Foreignkey fields if they are
        specified in the related_search_fields class attribute.
        """
        if (isinstance(db_field, models.ForeignKey) and 
            db_field.name in self.related_search_fields):
            model_name = db_field.rel.to._meta.object_name
            help_text = self.get_help_text(db_field.name, model_name)
            if kwargs.get('help_text'):
                help_text = u'%s %s' % (kwargs['help_text'], help_text)
            kwargs['widget'] = ForeignKeySearchInput(db_field.rel,
                                    self.related_search_fields[db_field.name])
            kwargs['help_text'] = help_text
        return super(ForeignKeyAutocompleteAdmin,
            self).formfield_for_dbfield(db_field, **kwargs)
