"""Service to handle user_token operations."""
import uuid
from datetime import datetime
from typing import Optional, Dict, Callable, Any

from flask_sqlalchemy import Pagination
from iso8601 import iso8601, ParseError

from corvus.db import db
from corvus.model import User, UserToken
from corvus.service.transformation_service import (
    BaseTransformer,
    register_transformer
)
from corvus import errors


@register_transformer
class UserTokenTransformer(BaseTransformer):
    """Serialize User model."""

    type = UserToken

    def _deserializers(
            self) -> Dict[str, Callable[[UserToken, Any], None]]:
        """Define the fields and the accompanying serializer factory."""
        return {
            'token': self.deserialize_token,
            'note': self.deserialize_note,
            'enabled': self.deserialize_enabled,
            'expirationTime': self.deserialize_expiration_time,
            'creationTime': self.deserialize_creation_time,
            'lastUsageTime': self.deserialize_last_usage_time,
            'version': self.deserialize_version
        }

    def _serializers(self) -> Dict[str, Callable[[], Any]]:
        """Define the fields and the accompanying serializer factory."""
        return {
            'token': self.serialize_token,
            'note': self.serialize_note,
            'enabled': self.serialize_enabled,
            'expirationTime': self.serialize_expiration_time,
            'creationTime': self.serialize_creation_time,
            'lastUsageTime': self.serialize_last_usage_time,
            'isValid': self.serialize_is_valid,
            'version': self.serialize_version
        }

    def serialize_token(self) -> str:
        """User token."""
        return self.model.token

    @staticmethod
    def deserialize_token(model: UserToken, token: str) -> None:
        """User token."""
        model.token = token

    def serialize_note(self) -> str:
        """User token note."""
        return self.model.note

    @staticmethod
    def deserialize_note(model: UserToken, note: str) -> None:
        """User token note."""
        model.note = note

    def serialize_enabled(self) -> bool:
        """User token enabled."""
        return self.model.enabled

    @staticmethod
    def deserialize_enabled(model: UserToken, enabled: bool) -> None:
        """User token enabled."""
        model.enabled = enabled

    def serialize_expiration_time(self) -> datetime:
        """User token expiration time."""
        return self.model.expiration_time

    @staticmethod
    def deserialize_expiration_time(
            model: UserToken, expiration_time: datetime) -> None:
        """User token expiration time."""
        try:
            model.expiration_time = iso8601.parse_date(expiration_time)
        except ParseError:
            raise errors.ValidationError(
                'Cannot parse datetime from %s' % expiration_time)

    def serialize_creation_time(self) -> datetime:
        """User token creation time."""
        return self.model.creation_time

    @staticmethod
    def deserialize_creation_time(
            model: UserToken, creation_time: datetime) -> None:
        """User token creation time."""
        try:
            model.creation_time = iso8601.parse_date(creation_time)
        except ParseError:
            raise errors.ValidationError(
                'Cannot parse datetime from %s' % creation_time)

    def serialize_last_usage_time(self) -> datetime:
        """User token last usage time."""
        return self.model.last_usage_time

    @staticmethod
    def deserialize_last_usage_time(
            model: UserToken, last_usage_time: datetime) -> None:
        """User token last usage time."""
        model.last_usage_time = iso8601.parse_date(last_usage_time)

    def serialize_is_valid(self):
        """User token is_valid computed value."""
        return is_valid_token(self.model)

    def serialize_version(self) -> int:
        """User token version."""
        return self.model.version

    @staticmethod
    def deserialize_version(model: UserToken, version: int) -> None:
        """User token version."""
        model.version = version


def generate_token() -> uuid.UUID:
    """
    Generate a unique token.

    :return:
    """
    return uuid.uuid4()


def create(
        user: User,
        note: Optional[str] = None,
        enabled: bool = True,
        expiration_time: Optional[datetime] = None) -> UserToken:
    """
    Create and save a UserToken.

    :param user: The User object to bind the token to
    :param note: An optional field to store additional information about a
    token
    :param enabled: A boolean to indicate whether a token can be considered
    eligible for authentication
    :param expiration_time: An optional argument to determine when the token
    becomes invalid as a means of authentication. Defaults to None, which means
    no expiration
    :return:
    """
    token = generate_token()
    user_token = UserToken(
        user_id=user.id,
        token=token.__str__(),
        note=note,
        enabled=enabled,
        creation_time=datetime.now(),
        expiration_time=expiration_time,
        version=0)

    db.session.add(user_token)
    db.session.commit()

    return user_token


def is_valid_token(user_token: Optional[UserToken]) -> bool:
    """
    Validate a token.

    Token must be enabled and if it has an expiration, it must be greater
    than now.

    :param user_token:
    :return:
    """
    if user_token is None:
        return False
    if not user_token.enabled:
        return False
    if (user_token.expiration_time is not None
            and user_token.expiration_time < datetime.utcnow()):
        return False
    return True


def delete(user_token: UserToken) -> bool:
    """
    Delete a user_token.

    :param user_token:
    :return:
    """
    existing_user_token = db.session.delete(user_token)
    if existing_user_token is None:
        db.session.commit()
        return True
    return False


def find_by_user_and_token(user: User, token: str) -> Optional[UserToken]:
    """
    Lookup a user_token by user and token string.

    :param user:
    :param token:
    :return:
    """
    return UserToken.query.filter_by(user_id=user.id, token=token).first()


def find_by_user(user: User, page: int, per_page: int = 20,
                 max_per_page: int = 100) -> Pagination:
    """
    Find all tokens for a user

    :param user: The user to find tokens for
    :param page: The page to request
    :param per_page: The number to get per page
    :param max_per_page:
    :return:
    """
    return UserToken.query.filter_by(
        user_id=user.id).paginate(page, per_page, True, max_per_page)