from django.db.models.base import ModelBase
from django.db import connection
from django.db import models
from django.db.models.fields.files import ImageFieldFile


class SafeImageFieldFile(ImageFieldFile):

    @property
    def width(self):
        try:
            return self.width
        except:
            return None

    @property
    def height(self):
        try:
            return self.height
        except:
            return None


class SafeImageField(models.ImageField):
    attr_class = SafeImageFieldFile


class ModelFieldsNames(object):
    def __init__(self, model):
        self.alias = None
        self._meta = model._meta

    def __getattr__(self, name):
        alias = '__as__'
        if name.startswith(alias):
            self.alias = name[len(alias):]
            return '%s as %s' % (self._meta.db_table, self.alias)
        field = self._meta.get_field(name).get_attname_column()[1]
        if self.alias:
            return u"%s.%s" % (self.alias, field)
        else:
            return u"%s.%s" % (self._meta.db_table, field)

    def __str__(self):
        return '%s' % self._meta.db_table


def format_sql(sql, **kwargs):
    for name, value in kwargs.items():
        if issubclass(type(value), ModelBase):
            kwargs[name] = ModelFieldsNames(value)
        elif isinstance(value, (tuple, list)):
            kwargs[name] = ','.join(map(lambda x: repr(x) if isinstance(x, str) else str(x), value))
        elif not isinstance(value, str):
            kwargs[name] = value
    return sql.format(**kwargs)


def execute_sql(sql, args=()):
    cursor = connection.cursor()
    cursor.execute(sql, args)
    return cursor.fetchall()