import smtplib
from random import choice

from django.contrib.auth.hashers import make_password
from django.contrib.auth.models import (
    AbstractBaseUser,
    BaseUserManager,
    Group as DjangoGroup,
    GroupManager as _GroupManager,
    Permission,
    PermissionsMixin,
)
from django.core import mail
from django.core.exceptions import ObjectDoesNotExist, ValidationError
from django.db import models
from django.db.models import Prefetch
from django.utils import timezone
from jsonfield import JSONField

from .access_permissions import (
    GroupAccessPermissions,
    PersonalNoteAccessPermissions,
    UserAccessPermissions,
)
from ..core.config import config
from ..utils.auth import GROUP_ADMIN_PK
from ..utils.models import CASCADE_AND_AUTOUODATE, RESTModelMixin


class UserManager(BaseUserManager):
    """
    Customized manager that creates new users only with a password and a
    username. It also supports our get_full_queryset method.
    """

    def get_full_queryset(self):
        """
        Returns the normal queryset with all users. In the background all
        groups are prefetched from the database together with all permissions
        and content types.
        """
        return self.get_queryset().prefetch_related(
            Prefetch(
                "groups",
                queryset=Group.objects.select_related("group_ptr").prefetch_related(
                    Prefetch(
                        "permissions",
                        queryset=Permission.objects.select_related("content_type"),
                    )
                ),
            )
        )

    def create_user(self, username, password, skip_autoupdate=False, **kwargs):
        """
        Creates a new user only with a password and a username.
        """
        user = self.model(username=username, **kwargs)
        user.set_password(password)
        user.save(skip_autoupdate=skip_autoupdate, using=self._db)
        return user

    def create_or_reset_admin_user(self):
        """
        Creates an user with the username 'admin'. If such a user already
        exists, resets it. The password is (re)set to 'admin'. The user
        becomes member of the group 'Admin'.
        """
        created = False
        try:
            admin = self.get(username="admin")
        except ObjectDoesNotExist:
            admin = self.model(username="admin", last_name="Administrator")
            created = True
        admin.default_password = "admin"
        admin.password = make_password(admin.default_password)
        admin.save(skip_autoupdate=True)
        admin.groups.add(GROUP_ADMIN_PK)
        return created

    def generate_username(self, first_name, last_name):
        """
        Generates a username from first name and last name.
        """
        first_name = first_name.strip()
        last_name = last_name.strip()

        if first_name and last_name:
            base_name = " ".join((first_name, last_name))
        else:
            base_name = first_name or last_name
            if not base_name:
                raise ValueError(
                    "Either 'first_name' or 'last_name' must not be " "empty."
                )

        if not self.filter(username=base_name).exists():
            generated_username = base_name
        else:
            counter = 0
            while True:
                counter += 1
                test_name = f"{base_name} {counter}"
                if not self.filter(username=test_name).exists():
                    generated_username = test_name
                    break

        return generated_username

    def generate_password(self):
        """
        Generates a random passwort. Do not use l, o, I, O, 1 or 0.
        """
        chars = "abcdefghijkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789"
        size = 8
        return "".join([choice(chars) for i in range(size)])


class User(RESTModelMixin, PermissionsMixin, AbstractBaseUser):
    """
    Model for users in OpenSlides. A client can login as an user with
    credentials. An user can also just be used as representation for a person
    in other OpenSlides apps like motion submitter or (assignment) election
    candidates.
    """

    access_permissions = UserAccessPermissions()

    USERNAME_FIELD = "username"

    username = models.CharField(max_length=255, unique=True, blank=True)

    first_name = models.CharField(max_length=255, blank=True)

    last_name = models.CharField(max_length=255, blank=True)

    gender = models.CharField(max_length=255, blank=True)

    email = models.EmailField(blank=True)

    last_email_send = models.DateTimeField(blank=True, null=True)

    # TODO: Try to remove the default argument in the following fields.

    structure_level = models.CharField(max_length=255, blank=True, default="")

    title = models.CharField(max_length=50, blank=True, default="")

    number = models.CharField(max_length=50, blank=True, default="")

    about_me = models.TextField(blank=True, default="")

    comment = models.TextField(blank=True, default="")

    default_password = models.CharField(max_length=100, blank=True, default="")

    is_active = models.BooleanField(default=True)

    is_present = models.BooleanField(default=False)

    is_committee = models.BooleanField(default=False)

    objects = UserManager()

    class Meta:
        default_permissions = ()
        permissions = (
            ("can_see_name", "Can see names of users"),
            (
                "can_see_extra_data",
                "Can see extra data of users (e.g. present and comment)",
            ),
            ("can_change_password", "Can change its own password"),
            ("can_manage", "Can manage users"),
        )
        ordering = ("last_name", "first_name", "username")

    def __str__(self):
        # Strip white spaces from the name parts
        first_name = self.first_name.strip()
        last_name = self.last_name.strip()

        # The user has a last_name and a first_name
        if first_name and last_name:
            name = " ".join((self.first_name, self.last_name))
        # The user has only a first_name or a last_name or no name
        else:
            name = first_name or last_name or self.username

        # Return result
        return name

    def save(self, *args, **kwargs):
        """
        Overridden method to skip autoupdate if only last_login field was
        updated as it is done during login.
        """
        if kwargs.get("update_fields") == ["last_login"]:
            kwargs["skip_autoupdate"] = True
        return super().save(*args, **kwargs)

    def has_perm(self, perm):
        """
        This method is closed. Do not use it but use openslides.utils.auth.has_perm.
        """
        raise RuntimeError(
            "Do not use user.has_perm() but use openslides.utils.auth.has_perm"
        )

    def send_invitation_email(
        self, connection, subject, message, skip_autoupdate=False
    ):
        """
        Sends an invitation email to the users. Returns True on success, False on failiure.
        May raise an ValidationError, if something went wrong.
        """
        if not self.email:
            return False

        # Custom dict class that for formatstrings with entries like {not_existent}
        # no error is raised and this is replaced with ''.
        class format_dict(dict):
            def __missing__(self, key):
                return ""

        message_format = format_dict(
            {
                "name": str(self),
                "event_name": config["general_event_name"],
                "url": config["users_pdf_url"],
                "username": self.username,
                "password": self.default_password,
            }
        )
        try:
            message = message.format(**message_format)
        except KeyError as err:
            raise ValidationError({"detail": f"Invalid property {err}."})

        subject_format = format_dict(
            {"event_name": config["general_event_name"], "username": self.username}
        )
        try:
            subject = subject.format(**subject_format)
        except KeyError as err:
            raise ValidationError({"detail": f"Invalid property {err}."})

        # Create an email and send it.
        email = mail.EmailMessage(
            subject, message, config["users_email_sender"], [self.email]
        )
        try:
            count = connection.send_messages([email])
        except smtplib.SMTPDataError as e:
            error = e.smtp_code
            helptext = ""
            if error == 554:
                helptext = " Is the email sender correct?"
            connection.close()
            raise ValidationError(
                {"detail": f"Error {error}. Cannot send email.{helptext}"}
            )
        except smtplib.SMTPRecipientsRefused:
            pass  # Run into returning false later
        else:
            if count == 1:
                self.email_send = True
                self.last_email_send = timezone.now()
                self.save(skip_autoupdate=skip_autoupdate)
                return True

        return False

    @property
    def session_auth_hash(self):
        """
        Returns the session auth hash of a user as attribute.

        Needed for the django rest framework.
        """
        return self.get_session_auth_hash()


class GroupManager(_GroupManager):
    """
    Customized manager that supports our get_full_queryset method.
    """

    def get_full_queryset(self):
        """
        Returns the normal queryset with all groups. In the background all
        permissions with the content types are prefetched from the database.
        """
        return (
            self.get_queryset()
            .select_related("group_ptr")
            .prefetch_related(
                Prefetch(
                    "permissions",
                    queryset=Permission.objects.select_related("content_type"),
                )
            )
        )


class Group(RESTModelMixin, DjangoGroup):
    """
    Extend the django group with support of our REST and caching system.
    """

    access_permissions = GroupAccessPermissions()
    objects = GroupManager()

    class Meta:
        default_permissions = ()


class PersonalNoteManager(models.Manager):
    """
    Customized model manager to support our get_full_queryset method.
    """

    def get_full_queryset(self):
        """
        Returns the normal queryset with all personal notes. In the background all
        users are prefetched from the database.
        """
        return self.get_queryset().select_related("user")


class PersonalNote(RESTModelMixin, models.Model):
    """
    Model for personal notes (e. g. likes/stars) of a user concerning different
    openslides objects like motions.
    """

    access_permissions = PersonalNoteAccessPermissions()

    objects = PersonalNoteManager()

    user = models.OneToOneField(User, on_delete=CASCADE_AND_AUTOUODATE)
    notes = JSONField()

    class Meta:
        default_permissions = ()