import uuid
from typing import Mapping, Optional, Type

from databases import Database
from pydantic import UUID4
from sqlalchemy import Boolean, Column, ForeignKey, Integer, String, Table, select
from sqlalchemy.dialects.postgresql import UUID
from sqlalchemy.ext.declarative import declared_attr
from sqlalchemy.types import CHAR, TypeDecorator

from fastapi_users.db.base import BaseUserDatabase
from fastapi_users.models import UD


class GUID(TypeDecorator):  # pragma: no cover
    """Platform-independent GUID type.

    Uses PostgreSQL's UUID type, otherwise uses
    CHAR(36), storing as regular strings.
    """

    impl = CHAR

    def load_dialect_impl(self, dialect):
        if dialect.name == "postgresql":
            return dialect.type_descriptor(UUID())
        else:
            return dialect.type_descriptor(CHAR(36))

    def process_bind_param(self, value, dialect):
        if value is None:
            return value
        elif dialect.name == "postgresql":
            return str(value)
        else:
            if not isinstance(value, uuid.UUID):
                return str(uuid.UUID(value))
            else:
                return str(value)

    def process_result_value(self, value, dialect):
        if value is None:
            return value
        else:
            if not isinstance(value, uuid.UUID):
                value = uuid.UUID(value)
            return value


class SQLAlchemyBaseUserTable:
    """Base SQLAlchemy users table definition."""

    __tablename__ = "user"

    id = Column(GUID, primary_key=True)
    email = Column(String, unique=True, index=True, nullable=False)
    hashed_password = Column(String, nullable=False)
    is_active = Column(Boolean, default=True, nullable=False)
    is_superuser = Column(Boolean, default=False, nullable=False)


class SQLAlchemyBaseOAuthAccountTable:
    """Base SQLAlchemy OAuth account table definition."""

    __tablename__ = "oauth_account"

    id = Column(GUID, primary_key=True)
    oauth_name = Column(String, index=True, nullable=False)
    access_token = Column(String, nullable=False)
    expires_at = Column(Integer, nullable=False)
    refresh_token = Column(String, nullable=True)
    account_id = Column(String, index=True, nullable=False)
    account_email = Column(String, nullable=False)

    @declared_attr
    def user_id(cls):
        return Column(GUID, ForeignKey("user.id", ondelete="cascade"), nullable=False)


class NotSetOAuthAccountTableError(Exception):
    """
    OAuth table was not set in DB adapter but was needed.

    Raised when trying to create/update a user with OAuth accounts set
    but no table were specified in the DB adapter.
    """

    pass


class SQLAlchemyUserDatabase(BaseUserDatabase[UD]):
    """
    Database adapter for SQLAlchemy.

    :param user_db_model: Pydantic model of a DB representation of a user.
    :param database: `Database` instance from `encode/databases`.
    :param users: SQLAlchemy users table instance.
    :param oauth_accounts: Optional SQLAlchemy OAuth accounts table instance.
    """

    database: Database
    users: Table
    oauth_accounts: Optional[Table]

    def __init__(
        self,
        user_db_model: Type[UD],
        database: Database,
        users: Table,
        oauth_accounts: Optional[Table] = None,
    ):
        super().__init__(user_db_model)
        self.database = database
        self.users = users
        self.oauth_accounts = oauth_accounts

    async def get(self, id: UUID4) -> Optional[UD]:
        query = self.users.select().where(self.users.c.id == id)
        user = await self.database.fetch_one(query)
        return await self._make_user(user) if user else None

    async def get_by_email(self, email: str) -> Optional[UD]:
        query = self.users.select().where(self.users.c.email == email)
        user = await self.database.fetch_one(query)
        return await self._make_user(user) if user else None

    async def get_by_oauth_account(self, oauth: str, account_id: str) -> Optional[UD]:
        if self.oauth_accounts is not None:
            query = (
                select([self.users])
                .select_from(self.users.join(self.oauth_accounts))
                .where(self.oauth_accounts.c.oauth_name == oauth)
                .where(self.oauth_accounts.c.account_id == account_id)
            )
            user = await self.database.fetch_one(query)
            return await self._make_user(user) if user else None
        raise NotSetOAuthAccountTableError()

    async def create(self, user: UD) -> UD:
        user_dict = user.dict()
        oauth_accounts_values = None

        if "oauth_accounts" in user_dict:
            oauth_accounts_values = []

            oauth_accounts = user_dict.pop("oauth_accounts")
            for oauth_account in oauth_accounts:
                oauth_accounts_values.append({"user_id": user.id, **oauth_account})

        query = self.users.insert()
        await self.database.execute(query, user_dict)

        if oauth_accounts_values is not None:
            if self.oauth_accounts is None:
                raise NotSetOAuthAccountTableError()
            query = self.oauth_accounts.insert()
            await self.database.execute_many(query, oauth_accounts_values)

        return user

    async def update(self, user: UD) -> UD:
        user_dict = user.dict()

        if "oauth_accounts" in user_dict:
            if self.oauth_accounts is None:
                raise NotSetOAuthAccountTableError()

            query = self.oauth_accounts.delete().where(
                self.oauth_accounts.c.user_id == user.id
            )
            await self.database.execute(query)

            oauth_accounts_values = []
            oauth_accounts = user_dict.pop("oauth_accounts")
            for oauth_account in oauth_accounts:
                oauth_accounts_values.append({"user_id": user.id, **oauth_account})

            query = self.oauth_accounts.insert()
            await self.database.execute_many(query, oauth_accounts_values)

        query = self.users.update().where(self.users.c.id == user.id).values(user_dict)
        await self.database.execute(query)
        return user

    async def delete(self, user: UD) -> None:
        query = self.users.delete().where(self.users.c.id == user.id)
        await self.database.execute(query)

    async def _make_user(self, user: Mapping) -> UD:
        user_dict = {**user}

        if self.oauth_accounts is not None:
            query = self.oauth_accounts.select().where(
                self.oauth_accounts.c.user_id == user["id"]
            )
            oauth_accounts = await self.database.fetch_all(query)
            user_dict["oauth_accounts"] = oauth_accounts

        return self.user_db_model(**user_dict)