stackpilot/backend/routers/auth.py

"""Authentication routes + first-launch setup wizard."""
from __future__ import annotations

import time
from collections import defaultdict, deque

from fastapi import APIRouter, Depends, HTTPException, Request, Response, status
from sqlmodel import Session, select

import auth as auth_mod
from database import get_session
from models.user import (
    LoginRequest,
    RefreshRequest,
    TokenPair,
    User,
    UserCreate,
    UserRead,
    UserUpdate,
)
from config import settings
from services import audit_service

router = APIRouter(prefix="/api/auth", tags=["auth"])

# Simple in-memory rate limiter for login (max 10 / minute / IP).
_LOGIN_HITS: dict[str, deque] = defaultdict(deque)
_RATE_LIMIT = 10
_RATE_WINDOW = 60.0


def _check_rate_limit(ip: str) -> None:
    now = time.monotonic()
    hits = _LOGIN_HITS[ip]
    while hits and now - hits[0] > _RATE_WINDOW:
        hits.popleft()
    if len(hits) >= _RATE_LIMIT:
        raise HTTPException(
            status_code=status.HTTP_429_TOO_MANY_REQUESTS,
            detail="Too many login attempts, slow down.",
        )
    hits.append(now)


#: The refresh cookie is scoped to the two endpoints that consume it, so it is
#: not attached to every API call the way a "/" cookie would be.
REFRESH_COOKIE = "stackpilot_refresh"
REFRESH_COOKIE_PATH = "/api/auth"


def _issue(
    user: User, response: Response, request: Request, in_body: bool = False
) -> TokenPair:
    """Mint a token pair, putting the refresh token in an httpOnly cookie.

    Keeping the long-lived token out of JavaScript's reach means a successful
    XSS can no longer walk off with 30 days of access — it is limited to
    whatever it can do in the live page. The short-lived access token still
    goes to the client, which holds it in memory only.

    ``in_body`` returns it in the response as well, for scripted clients that
    have no cookie jar.
    """
    refresh = auth_mod.create_refresh_token(user)
    response.set_cookie(
        REFRESH_COOKIE,
        refresh,
        max_age=settings.REFRESH_TOKEN_EXPIRE_DAYS * 24 * 3600,
        httponly=True,
        # Lax rather than Strict so following a link into StackPilot keeps you
        # signed in; the cookie is only ever read by same-site POSTs anyway.
        samesite="lax",
        # Only when the request actually arrived over TLS — marking it Secure on
        # a plain-HTTP homelab deployment would make the browser drop it and
        # nobody could stay signed in. request.url.scheme is trustworthy here
        # because uvicorn runs with --proxy-headers.
        secure=request.url.scheme == "https",
        path=REFRESH_COOKIE_PATH,
    )
    return TokenPair(
        access_token=auth_mod.create_access_token(user),
        refresh_token=refresh if in_body else None,
    )


@router.get("/needs-setup")
def needs_setup(session: Session = Depends(get_session)) -> dict:
    """First-launch wizard check: True if no users exist yet."""
    return {"needs_setup": not auth_mod.users_exist(session)}


@router.post("/setup", response_model=TokenPair)
def setup(
    body: UserCreate,
    request: Request,
    response: Response,
    in_body: bool = False,
    session: Session = Depends(get_session),
) -> TokenPair:
    if auth_mod.users_exist(session):
        raise HTTPException(status_code=400, detail="Setup already completed")
    user = User(
        username=body.username,
        hashed_password=auth_mod.hash_password(body.password),
        role="admin",
    )
    session.add(user)
    session.commit()
    session.refresh(user)
    audit_service.record(
        session, user=user.username, action="user.setup", target=user.username
    )
    return _issue(user, response, request, in_body)


@router.post("/login", response_model=TokenPair)
def login(
    body: LoginRequest,
    request: Request,
    response: Response,
    in_body: bool = False,
    session: Session = Depends(get_session),
) -> TokenPair:
    ip = request.client.host if request.client else "unknown"
    _check_rate_limit(ip)
    user = auth_mod.authenticate(session, body.username, body.password)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect username or password",
        )
    audit_service.record(
        session, user=user.username, action="auth.login", target=user.username, ip=ip
    )
    return _issue(user, response, request, in_body)


@router.post("/refresh", response_model=TokenPair)
def refresh(
    request: Request,
    response: Response,
    body: RefreshRequest | None = None,
    in_body: bool = False,
    session: Session = Depends(get_session),
) -> TokenPair:
    """Exchange a refresh token for a fresh pair.

    Reads the httpOnly cookie; a body is accepted as a fallback for clients
    that cannot hold one. The token is re-validated against the live user, so a
    password reset or a disabled account takes effect here too rather than at
    the end of the token's 30-day life.
    """
    token = request.cookies.get(REFRESH_COOKIE) or (body.refresh_token if body else None)
    if not token:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED, detail="No refresh token"
        )
    payload = auth_mod.decode_token(token, "refresh")
    user = auth_mod.resolve_token_user(session, payload)
    if not user:
        response.delete_cookie(REFRESH_COOKIE, path=REFRESH_COOKIE_PATH)
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Session is no longer valid — sign in again",
        )
    return _issue(user, response, request, in_body)


@router.post("/logout")
def logout(request: Request, response: Response) -> dict:
    """End the session on this device by dropping the refresh cookie.

    Deliberately does not bump ``token_version``: signing out on your phone
    should not kill the session on your desktop. Use "sign out everywhere"
    for that. The access token is held in memory by the client and dies with
    the tab; it stays technically valid for the rest of its hour, which is why
    it is short-lived.
    """
    response.delete_cookie(REFRESH_COOKIE, path=REFRESH_COOKIE_PATH)
    return {"ok": True}


@router.post("/logout-everywhere")
def logout_everywhere(
    request: Request,
    response: Response,
    session: Session = Depends(get_session),
    user: User = Depends(auth_mod.get_current_user),
) -> dict:
    """Revoke every token this account holds, on every device."""
    auth_mod.bump_token_version(user)
    session.add(user)
    session.commit()
    response.delete_cookie(REFRESH_COOKIE, path=REFRESH_COOKIE_PATH)
    audit_service.record(
        session, user=user.username, action="auth.logout_everywhere",
        target=user.username, ip=_ip(request),
    )
    return {"ok": True}


@router.get("/me", response_model=UserRead)
def me(user: User = Depends(auth_mod.get_current_user)) -> User:
    return user


# --------------------------------------------------------------------------- #
# User management (admin only)
# --------------------------------------------------------------------------- #


def _ip(request: Request) -> str:
    return request.client.host if request.client else "unknown"


@router.get("/users", response_model=list[UserRead])
def list_users(
    session: Session = Depends(get_session),
    _admin: User = Depends(auth_mod.require_admin),
) -> list[User]:
    return session.exec(select(User).order_by(User.id)).all()


@router.post("/users", response_model=UserRead, status_code=201)
def create_user(
    body: UserCreate,
    request: Request,
    session: Session = Depends(get_session),
    admin: User = Depends(auth_mod.require_admin),
) -> User:
    if not body.username.strip() or not body.password:
        raise HTTPException(status_code=400, detail="Username and password required")
    if auth_mod.get_user(session, body.username):
        raise HTTPException(status_code=409, detail="Username already exists")
    role = body.role if body.role in ("admin", "user") else "user"
    user = User(
        username=body.username,
        hashed_password=auth_mod.hash_password(body.password),
        role=role,
    )
    session.add(user)
    session.commit()
    session.refresh(user)
    audit_service.record(
        session, user=admin.username, action="user.create", target=user.username,
        detail=f"role={role}", ip=_ip(request),
    )
    return user


@router.patch("/users/{user_id}", response_model=UserRead)
def update_user(
    user_id: int,
    body: UserUpdate,
    request: Request,
    session: Session = Depends(get_session),
    admin: User = Depends(auth_mod.require_admin),
) -> User:
    user = session.get(User, user_id)
    if not user:
        raise HTTPException(status_code=404, detail="User not found")
    # Guard against locking yourself out / demoting the last admin.
    demoting = (body.role is not None and body.role != "admin") or body.is_active is False
    if user.role == "admin" and demoting:
        other_admins = session.exec(
            select(User).where(User.role == "admin", User.is_active == True, User.id != user_id)  # noqa: E712
        ).first()
        if not other_admins:
            raise HTTPException(status_code=400, detail="Cannot demote or disable the last active admin")
    # Any of these three changes what this account is allowed to do, so the
    # tokens it already holds must stop working. Without the bump a password
    # reset was cosmetic: whoever had the old tokens kept full access for up to
    # 30 days, and a demotion or a disable only took effect once they expired.
    authority_changed = (
        bool(body.password)
        or (body.role is not None and body.role != user.role)
        or (body.is_active is not None and body.is_active != user.is_active)
    )
    if body.password:
        user.hashed_password = auth_mod.hash_password(body.password)
    if body.role is not None:
        if body.role not in ("admin", "user"):
            raise HTTPException(status_code=400, detail="Invalid role")
        user.role = body.role
    if body.is_active is not None:
        user.is_active = body.is_active
    if authority_changed:
        auth_mod.bump_token_version(user)
    session.add(user)
    session.commit()
    session.refresh(user)
    audit_service.record(
        session, user=admin.username, action="user.update", target=user.username,
        ip=_ip(request),
    )
    return user


@router.delete("/users/{user_id}")
def delete_user(
    user_id: int,
    request: Request,
    session: Session = Depends(get_session),
    admin: User = Depends(auth_mod.require_admin),
) -> dict:
    user = session.get(User, user_id)
    if not user:
        raise HTTPException(status_code=404, detail="User not found")
    if user.id == admin.id:
        raise HTTPException(status_code=400, detail="You cannot delete your own account")
    if user.role == "admin":
        other_admins = session.exec(
            select(User).where(User.role == "admin", User.is_active == True, User.id != user_id)  # noqa: E712
        ).first()
        if not other_admins:
            raise HTTPException(status_code=400, detail="Cannot delete the last active admin")
    username = user.username
    session.delete(user)
    session.commit()
    audit_service.record(
        session, user=admin.username, action="user.delete", target=username,
        ip=_ip(request),
    )
    return {"ok": True}