"""A long-lived key to a short-lived one.

An access token here lasts a day and cannot be withdrawn: it is a signed
statement, and nothing consults a table before believing it. That is workable
for a browser, which can send the person back to a login form, and no use at
all to an app on a phone — which would have to keep the password to survive a
day, and that is the one thing a client must never store.

So a refresh token is a row, not a signature. It can be listed, it can be
withdrawn, and it is stored the way a password is: only the hash, because a
database that leaks should not hand over live sessions with it.

Rotation on every use is what makes a stolen one survivable. Each refresh
issues a new token and marks the old one used; if a thief spends it first, the
real client's next attempt presents a token already spent, and the whole family
is withdrawn — the theft turns itself in.
"""
from datetime import datetime

from sqlalchemy import Column, DateTime, ForeignKey, Integer, String

from app.database import Base


class RefreshToken(Base):
    __tablename__ = "refresh_tokens"

    id = Column(Integer, primary_key=True, index=True)
    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
    #: SHA-256 of the token. The token itself is shown once, at issue.
    token_hash = Column(String(64), unique=True, nullable=False, index=True)
    #: Every token descended from one sign-in shares this. Withdrawing a family
    #: ends the session, however many times it has been rotated.
    family = Column(String(32), nullable=False, index=True)
    #: What asked for it, as the client described itself. For the list of
    #: sessions a person is shown when they ask where they are signed in.
    label = Column(String(120), nullable=True)
    created_at = Column(DateTime, default=datetime.utcnow)
    expires_at = Column(DateTime, nullable=False)
    #: Set when it is spent. A spent token presented again is theft or a bug,
    #: and both are handled the same way: end the family.
    used_at = Column(DateTime, nullable=True)
    revoked_at = Column(DateTime, nullable=True)
    last_ip = Column(String(64), nullable=True)