try:
    set
except NameError:
    from sets import Set as set   # Python 2.3 fallback

from django.core.exceptions import ImproperlyConfigured
from django.db import models
from django.forms.models import BaseModelForm, BaseModelFormSet, fields_for_model
from django.contrib.admin.options import flatten_fieldsets, BaseModelAdmin
from django.contrib.admin.options import HORIZONTAL, VERTICAL

__all__ = ['validate']

def validate(cls, model):
    """
    Does basic ModelAdmin option validation. Calls custom validation
    classmethod in the end if it is provided in cls. The signature of the
    custom validation classmethod should be: def validate(cls, model).
    """
    # Before we can introspect models, they need to be fully loaded so that
    # inter-relations are set up correctly. We force that here.
    models.get_apps()

    opts = model._meta
    validate_base(cls, model)

    # list_display
    if hasattr(cls, 'list_display'):
        check_isseq(cls, 'list_display', cls.list_display)
        for idx, field in enumerate(cls.list_display):
            if not callable(field):
                if not hasattr(cls, field):
                    if not hasattr(model, field):
                        try:
                            opts.get_field(field)
                        except models.FieldDoesNotExist:
                            raise ImproperlyConfigured("%s.list_display[%d], %r is not a callable or an attribute of %r or found in the model %r."
                                % (cls.__name__, idx, field, cls.__name__, model._meta.object_name))
                        f = fetch_attr(cls, model, opts, "list_display[%d]" % idx, field)
                        if isinstance(f, models.ManyToManyField):
                            raise ImproperlyConfigured("'%s.list_display[%d]', '%s' is a ManyToManyField which is not supported."
                                % (cls.__name__, idx, field))

    # list_display_links
    if hasattr(cls, 'list_display_links'):
        check_isseq(cls, 'list_display_links', cls.list_display_links)
        for idx, field in enumerate(cls.list_display_links):
            fetch_attr(cls, model, opts, 'list_display_links[%d]' % idx, field)
            if field not in cls.list_display:
                raise ImproperlyConfigured("'%s.list_display_links[%d]'"
                        "refers to '%s' which is not defined in 'list_display'."
                        % (cls.__name__, idx, field))

    # list_filter
    if hasattr(cls, 'list_filter'):
        check_isseq(cls, 'list_filter', cls.list_filter)
        for idx, field in enumerate(cls.list_filter):
            get_field(cls, model, opts, 'list_filter[%d]' % idx, field)

    # list_per_page = 100
    if hasattr(cls, 'list_per_page') and not isinstance(cls.list_per_page, int):
        raise ImproperlyConfigured("'%s.list_per_page' should be a integer."
                % cls.__name__)

    # search_fields = ()
    if hasattr(cls, 'search_fields'):
        check_isseq(cls, 'search_fields', cls.search_fields)

    # date_hierarchy = None
    if cls.date_hierarchy:
        f = get_field(cls, model, opts, 'date_hierarchy', cls.date_hierarchy)
        if not isinstance(f, (models.DateField, models.DateTimeField)):
            raise ImproperlyConfigured("'%s.date_hierarchy is "
                    "neither an instance of DateField nor DateTimeField."
                    % cls.__name__)

    # ordering = None
    if cls.ordering:
        check_isseq(cls, 'ordering', cls.ordering)
        for idx, field in enumerate(cls.ordering):
            if field == '?' and len(cls.ordering) != 1:
                raise ImproperlyConfigured("'%s.ordering' has the random "
                        "ordering marker '?', but contains other fields as "
                        "well. Please either remove '?' or the other fields."
                        % cls.__name__)
            if field == '?':
                continue
            if field.startswith('-'):
                field = field[1:]
            # Skip ordering in the format field1__field2 (FIXME: checking
            # this format would be nice, but it's a little fiddly).
            if '__' in field:
                continue
            get_field(cls, model, opts, 'ordering[%d]' % idx, field)

    # list_select_related = False
    # save_as = False
    # save_on_top = False
    for attr in ('list_select_related', 'save_as', 'save_on_top'):
        if not isinstance(getattr(cls, attr), bool):
            raise ImproperlyConfigured("'%s.%s' should be a boolean."
                    % (cls.__name__, attr))

    # inlines = []
    if hasattr(cls, 'inlines'):
        check_isseq(cls, 'inlines', cls.inlines)
        for idx, inline in enumerate(cls.inlines):
            if not issubclass(inline, BaseModelAdmin):
                raise ImproperlyConfigured("'%s.inlines[%d]' does not inherit "
                        "from BaseModelAdmin." % (cls.__name__, idx))
            if not inline.model:
                raise ImproperlyConfigured("'model' is a required attribute "
                        "of '%s.inlines[%d]'." % (cls.__name__, idx))
            if not issubclass(inline.model, models.Model):
                raise ImproperlyConfigured("'%s.inlines[%d].model' does not "
                        "inherit from models.Model." % (cls.__name__, idx))
            validate_base(inline, inline.model)
            validate_inline(inline)

def validate_inline(cls):
    # model is already verified to exist and be a Model
    if cls.fk_name: # default value is None
        f = get_field(cls, cls.model, cls.model._meta, 'fk_name', cls.fk_name)
        if not isinstance(f, models.ForeignKey):
            raise ImproperlyConfigured("'%s.fk_name is not an instance of "
                    "models.ForeignKey." % cls.__name__)
    # extra = 3
    # max_num = 0
    for attr in ('extra', 'max_num'):
        if not isinstance(getattr(cls, attr), int):
            raise ImproperlyConfigured("'%s.%s' should be a integer."
                    % (cls.__name__, attr))

    # formset
    if hasattr(cls, 'formset') and not issubclass(cls.formset, BaseModelFormSet):
        raise ImproperlyConfigured("'%s.formset' does not inherit from "
                "BaseModelFormSet." % cls.__name__)

def validate_base(cls, model):
    opts = model._meta

    # raw_id_fields
    if hasattr(cls, 'raw_id_fields'):
        check_isseq(cls, 'raw_id_fields', cls.raw_id_fields)
        for idx, field in enumerate(cls.raw_id_fields):
            f = get_field(cls, model, opts, 'raw_id_fields', field)
            if not isinstance(f, (models.ForeignKey, models.ManyToManyField)):
                raise ImproperlyConfigured("'%s.raw_id_fields[%d]', '%s' must "
                        "be either a ForeignKey or ManyToManyField."
                        % (cls.__name__, idx, field))

    # fields
    if cls.fields: # default value is None
        check_isseq(cls, 'fields', cls.fields)
        for field in cls.fields:
            check_formfield(cls, model, opts, 'fields', field)
        if cls.fieldsets:
            raise ImproperlyConfigured('Both fieldsets and fields are specified in %s.' % cls.__name__)
        if len(cls.fields) > len(set(cls.fields)):
            raise ImproperlyConfigured('There are duplicate field(s) in %s.fields' % cls.__name__)

    # fieldsets
    if cls.fieldsets: # default value is None
        check_isseq(cls, 'fieldsets', cls.fieldsets)
        for idx, fieldset in enumerate(cls.fieldsets):
            check_isseq(cls, 'fieldsets[%d]' % idx, fieldset)
            if len(fieldset) != 2:
                raise ImproperlyConfigured("'%s.fieldsets[%d]' does not "
                        "have exactly two elements." % (cls.__name__, idx))
            check_isdict(cls, 'fieldsets[%d][1]' % idx, fieldset[1])
            if 'fields' not in fieldset[1]:
                raise ImproperlyConfigured("'fields' key is required in "
                        "%s.fieldsets[%d][1] field options dict."
                        % (cls.__name__, idx))
        flattened_fieldsets = flatten_fieldsets(cls.fieldsets)
        if len(flattened_fieldsets) > len(set(flattened_fieldsets)):
            raise ImproperlyConfigured('There are duplicate field(s) in %s.fieldsets' % cls.__name__)
        for field in flattened_fieldsets:
            check_formfield(cls, model, opts, "fieldsets[%d][1]['fields']" % idx, field)

    # form
    if hasattr(cls, 'form') and not issubclass(cls.form, BaseModelForm):
        raise ImproperlyConfigured("%s.form does not inherit from "
                "BaseModelForm." % cls.__name__)

    # filter_vertical
    if hasattr(cls, 'filter_vertical'):
        check_isseq(cls, 'filter_vertical', cls.filter_vertical)
        for idx, field in enumerate(cls.filter_vertical):
            f = get_field(cls, model, opts, 'filter_vertical', field)
            if not isinstance(f, models.ManyToManyField):
                raise ImproperlyConfigured("'%s.filter_vertical[%d]' must be "
                    "a ManyToManyField." % (cls.__name__, idx))

    # filter_horizontal
    if hasattr(cls, 'filter_horizontal'):
        check_isseq(cls, 'filter_horizontal', cls.filter_horizontal)
        for idx, field in enumerate(cls.filter_horizontal):
            f = get_field(cls, model, opts, 'filter_horizontal', field)
            if not isinstance(f, models.ManyToManyField):
                raise ImproperlyConfigured("'%s.filter_horizontal[%d]' must be "
                    "a ManyToManyField." % (cls.__name__, idx))

    # radio_fields
    if hasattr(cls, 'radio_fields'):
        check_isdict(cls, 'radio_fields', cls.radio_fields)
        for field, val in cls.radio_fields.items():
            f = get_field(cls, model, opts, 'radio_fields', field)
            if not (isinstance(f, models.ForeignKey) or f.choices):
                raise ImproperlyConfigured("'%s.radio_fields['%s']' "
                        "is neither an instance of ForeignKey nor does "
                        "have choices set." % (cls.__name__, field))
            if not val in (HORIZONTAL, VERTICAL):
                raise ImproperlyConfigured("'%s.radio_fields['%s']' "
                        "is neither admin.HORIZONTAL nor admin.VERTICAL."
                        % (cls.__name__, field))

    # prepopulated_fields
    if hasattr(cls, 'prepopulated_fields'):
        check_isdict(cls, 'prepopulated_fields', cls.prepopulated_fields)
        for field, val in cls.prepopulated_fields.items():
            f = get_field(cls, model, opts, 'prepopulated_fields', field)
            if isinstance(f, (models.DateTimeField, models.ForeignKey,
                models.ManyToManyField)):
                raise ImproperlyConfigured("'%s.prepopulated_fields['%s']' "
                        "is either a DateTimeField, ForeignKey or "
                        "ManyToManyField. This isn't allowed."
                        % (cls.__name__, field))
            check_isseq(cls, "prepopulated_fields['%s']" % field, val)
            for idx, f in enumerate(val):
                get_field(cls, model, opts, "prepopulated_fields['%s'][%d]" % (field, idx), f)

def check_isseq(cls, label, obj):
    if not isinstance(obj, (list, tuple)):
        raise ImproperlyConfigured("'%s.%s' must be a list or tuple." % (cls.__name__, label))

def check_isdict(cls, label, obj):
    if not isinstance(obj, dict):
        raise ImproperlyConfigured("'%s.%s' must be a dictionary." % (cls.__name__, label))

def get_field(cls, model, opts, label, field):
    try:
        return opts.get_field(field)
    except models.FieldDoesNotExist:
        raise ImproperlyConfigured("'%s.%s' refers to field '%s' that is missing from model '%s'."
                % (cls.__name__, label, field, model.__name__))

def check_formfield(cls, model, opts, label, field):
    if getattr(cls.form, 'base_fields', None):
        try:
            cls.form.base_fields[field]
        except KeyError:
            raise ImproperlyConfigured("'%s.%s' refers to field '%s' that "
                "is missing from the form." % (cls.__name__, label, field))
    else:
        fields = fields_for_model(model)
        try:
            fields[field]
        except KeyError:
            raise ImproperlyConfigured("'%s.%s' refers to field '%s' that "
                "is missing from the form." % (cls.__name__, label, field))

def fetch_attr(cls, model, opts, label, field):
    try:
        return opts.get_field(field)
    except models.FieldDoesNotExist:
        pass
    try:
        return getattr(model, field)
    except AttributeError:
        raise ImproperlyConfigured("'%s.%s' refers to '%s' that is neither a field, method or property of model '%s'."
            % (cls.__name__, label, field, model.__name__))