from django.contrib import auth
from django.core import validators
from django.core.exceptions import ImproperlyConfigured
from django.db import models
from django.db.models.manager import EmptyManager
from django.contrib.contenttypes.models import ContentType
from django.utils.encoding import smart_str
from django.utils.translation import ugettext_lazy as _
import datetime
import urllib

UNUSABLE_PASSWORD = '!' # This will never be a valid hash

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

def get_hexdigest(algorithm, salt, raw_password):
    """
    Returns a string of the hexdigest of the given plaintext password and salt
    using the given algorithm ('md5', 'sha1' or 'crypt').
    """
    raw_password, salt = smart_str(raw_password), smart_str(salt)
    if algorithm == 'crypt':
        try:
            import crypt
        except ImportError:
            raise ValueError('"crypt" password algorithm not supported in this environment')
        return crypt.crypt(raw_password, salt)
    # The rest of the supported algorithms are supported by hashlib, but
    # hashlib is only available in Python 2.5.
    try:
        import hashlib
    except ImportError:
        if algorithm == 'md5':
            import md5
            return md5.new(salt + raw_password).hexdigest()
        elif algorithm == 'sha1':
            import sha
            return sha.new(salt + raw_password).hexdigest()
    else:
        if algorithm == 'md5':
            return hashlib.md5(salt + raw_password).hexdigest()
        elif algorithm == 'sha1':
            return hashlib.sha1(salt + raw_password).hexdigest()
    raise ValueError("Got unknown password algorithm type in password.")

def check_password(raw_password, enc_password):
    """
    Returns a boolean of whether the raw_password was correct. Handles
    encryption formats behind the scenes.
    """
    algo, salt, hsh = enc_password.split('$')
    return hsh == get_hexdigest(algo, salt, raw_password)

class SiteProfileNotAvailable(Exception):
    pass

class Permission(models.Model):
    """The permissions system provides a way to assign permissions to specific users and groups of users.

    The permission system is used by the Django admin site, but may also be useful in your own code. The Django admin site uses permissions as follows:

        - The "add" permission limits the user's ability to view the "add" form and add an object.
        - The "change" permission limits a user's ability to view the change list, view the "change" form and change an object.
        - The "delete" permission limits the ability to delete an object.

    Permissions are set globally per type of object, not per specific object instance. It is possible to say "Mary may change news stories," but it's not currently possible to say "Mary may change news stories, but only the ones she created herself" or "Mary may only change news stories that have a certain status or publication date."

    Three basic permissions -- add, change and delete -- are automatically created for each Django model.
    """
    name = models.CharField(_('name'), max_length=50)
    content_type = models.ForeignKey(ContentType)
    codename = models.CharField(_('codename'), max_length=100)

    class Meta:
        verbose_name = _('permission')
        verbose_name_plural = _('permissions')
        unique_together = (('content_type', 'codename'),)
        ordering = ('content_type', 'codename')

    def __unicode__(self):
        return u"%s | %s | %s" % (self.content_type.app_label, self.content_type, self.name)

class Group(models.Model):
    """Groups are a generic way of categorizing users to apply permissions, or some other label, to those users. A user can belong to any number of groups.

    A user in a group automatically has all the permissions granted to that group. For example, if the group Site editors has the permission can_edit_home_page, any user in that group will have that permission.

    Beyond permissions, groups are a convenient way to categorize users to apply some label, or extended functionality, to them. For example, you could create a group 'Special users', and you could write code that would do special things to those users -- such as giving them access to a members-only portion of your site, or sending them members-only e-mail messages.
    """
    name = models.CharField(_('name'), max_length=80, unique=True)
    permissions = models.ManyToManyField(Permission, verbose_name=_('permissions'), blank=True, filter_interface=models.HORIZONTAL)

    class Meta:
        verbose_name = _('group')
        verbose_name_plural = _('groups')
        ordering = ('name',)

    class Admin:
        search_fields = ('name',)

    def __unicode__(self):
        return self.name

class UserManager(models.Manager):
    def create_user(self, username, email, password=None):
        "Creates and saves a User with the given username, e-mail and password."
        now = datetime.datetime.now()
        user = self.model(None, username, '', '', email.strip().lower(), 'placeholder', False, True, False, now, now)
        if password:
            user.set_password(password)
        else:
            user.set_unusable_password()
        user.save()
        return user

    def create_superuser(self, username, email, password):
        u = self.create_user(username, email, password)
        u.is_staff = True
        u.is_active = True
        u.is_superuser = True
        u.save()

    def make_random_password(self, length=10, allowed_chars='abcdefghjkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789'):
        "Generates a random password with the given length and given allowed_chars"
        # Note that default value of allowed_chars does not have "I" or letters
        # that look like it -- just to avoid confusion.
        from random import choice
        return ''.join([choice(allowed_chars) for i in range(length)])

class User(models.Model):
    """Users within the Django authentication system are represented by this model.

    Username and password are required. Other fields are optional.
    """
    username = models.CharField(_('username'), max_length=30, unique=True, validator_list=[validators.isAlphaNumeric], help_text=_("Required. 30 characters or fewer. Alphanumeric characters only (letters, digits and underscores)."))
    first_name = models.CharField(_('first name'), max_length=30, blank=True)
    last_name = models.CharField(_('last name'), max_length=30, blank=True)
    email = models.EmailField(_('e-mail address'), blank=True)
    password = models.CharField(_('password'), max_length=128, help_text=_("Use '[algo]$[salt]$[hexdigest]' or use the <a href=\"password/\">change password form</a>."))
    is_staff = models.BooleanField(_('staff status'), default=False, help_text=_("Designates whether the user can log into this admin site."))
    is_active = models.BooleanField(_('active'), default=True, help_text=_("Designates whether this user should be treated as active. Unselect this instead of deleting accounts."))
    is_superuser = models.BooleanField(_('superuser status'), default=False, help_text=_("Designates that this user has all permissions without explicitly assigning them."))
    last_login = models.DateTimeField(_('last login'), default=datetime.datetime.now)
    date_joined = models.DateTimeField(_('date joined'), default=datetime.datetime.now)
    groups = models.ManyToManyField(Group, verbose_name=_('groups'), blank=True,
        help_text=_("In addition to the permissions manually assigned, this user will also get all permissions granted to each group he/she is in."))
    user_permissions = models.ManyToManyField(Permission, verbose_name=_('user permissions'), blank=True, filter_interface=models.HORIZONTAL)
    objects = UserManager()

    class Meta:
        verbose_name = _('user')