First product

app/auth/__init__.py

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+"""Authentication package for scholarr."""
+

app/auth/deps.py

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+from __future__ import annotations
+
+from functools import lru_cache
+
+from app.auth.rate_limit import SlidingWindowRateLimiter
+from app.auth.security import PasswordService
+from app.auth.service import AuthService
+from app.settings import settings
+
+
+@lru_cache
+def get_password_service() -> PasswordService:
+    return PasswordService()
+
+
+@lru_cache
+def get_auth_service() -> AuthService:
+    return AuthService(password_service=get_password_service())
+
+
+@lru_cache
+def get_login_rate_limiter() -> SlidingWindowRateLimiter:
+    return SlidingWindowRateLimiter(
+        max_attempts=settings.login_rate_limit_attempts,
+        window_seconds=settings.login_rate_limit_window_seconds,
+    )
+

app/auth/rate_limit.py

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+from __future__ import annotations
+
+from collections import defaultdict, deque
+from collections.abc import Callable
+from dataclasses import dataclass
+from math import ceil
+from threading import Lock
+from time import monotonic
+
+
+@dataclass(frozen=True)
+class RateLimitDecision:
+    allowed: bool
+    retry_after_seconds: int = 0
+
+
+class SlidingWindowRateLimiter:
+    def __init__(
+        self,
+        *,
+        max_attempts: int,
+        window_seconds: int,
+        now: Callable[[], float] = monotonic,
+    ) -> None:
+        self._max_attempts = max_attempts
+        self._window_seconds = window_seconds
+        self._now = now
+        self._attempts: dict[str, deque[float]] = defaultdict(deque)
+        self._lock = Lock()
+
+    def check(self, key: str) -> RateLimitDecision:
+        with self._lock:
+            now_value = self._now()
+            attempts = self._attempts[key]
+            self._trim_expired(attempts, now_value)
+            if len(attempts) >= self._max_attempts:
+                retry_after = self._window_seconds - (now_value - attempts[0])
+                return RateLimitDecision(
+                    allowed=False,
+                    retry_after_seconds=max(1, ceil(retry_after)),
+                )
+            return RateLimitDecision(allowed=True)
+
+    def record_failure(self, key: str) -> None:
+        with self._lock:
+            now_value = self._now()
+            attempts = self._attempts[key]
+            self._trim_expired(attempts, now_value)
+            attempts.append(now_value)
+
+    def reset(self, key: str) -> None:
+        with self._lock:
+            self._attempts.pop(key, None)
+
+    def clear_all(self) -> None:
+        with self._lock:
+            self._attempts.clear()
+
+    def _trim_expired(self, attempts: deque[float], now_value: float) -> None:
+        while attempts and now_value - attempts[0] >= self._window_seconds:
+            attempts.popleft()
+

app/auth/security.py

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+from __future__ import annotations
+
+from argon2 import PasswordHasher
+from argon2.exceptions import InvalidHashError, VerificationError
+
+
+class PasswordService:
+    def __init__(self, hasher: PasswordHasher | None = None) -> None:
+        self._hasher = hasher or PasswordHasher()
+
+    def hash_password(self, password: str) -> str:
+        return self._hasher.hash(password)
+
+    def verify_password(self, password_hash: str, password: str) -> bool:
+        try:
+            return bool(self._hasher.verify(password_hash, password))
+        except (InvalidHashError, VerificationError):
+            return False
+

app/auth/service.py

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+from __future__ import annotations
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.auth.security import PasswordService
+from app.db.models import User
+
+
+class AuthService:
+    def __init__(self, password_service: PasswordService) -> None:
+        self._password_service = password_service
+
+    async def authenticate_user(
+        self,
+        db_session: AsyncSession,
+        *,
+        email: str,
+        password: str,
+    ) -> User | None:
+        normalized_email = email.strip().lower()
+        if not normalized_email or not password:
+            return None
+        result = await db_session.execute(
+            select(User).where(User.email == normalized_email)
+        )
+        user = result.scalar_one_or_none()
+        if user is None or not user.is_active:
+            return None
+        if not self._password_service.verify_password(user.password_hash, password):
+            return None
+        return user
+
+    def hash_password(self, password: str) -> str:
+        return self._password_service.hash_password(password)
+
+    def verify_password(self, *, password_hash: str, password: str) -> bool:
+        return self._password_service.verify_password(password_hash, password)

app/auth/session.py

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+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from starlette.requests import Request
+
+
+SESSION_USER_ID_KEY = "auth_user_id"
+SESSION_USER_EMAIL_KEY = "auth_user_email"
+SESSION_USER_IS_ADMIN_KEY = "auth_user_is_admin"
+
+
+@dataclass(frozen=True)
+class SessionUser:
+    id: int
+    email: str
+    is_admin: bool
+
+
+def get_session_user(request: Request) -> SessionUser | None:
+    user_id = request.session.get(SESSION_USER_ID_KEY)
+    email = request.session.get(SESSION_USER_EMAIL_KEY)
+    is_admin = request.session.get(SESSION_USER_IS_ADMIN_KEY)
+    if user_id is None or email is None or is_admin is None:
+        return None
+    try:
+        parsed_user_id = int(user_id)
+    except (TypeError, ValueError):
+        return None
+    if not isinstance(email, str):
+        return None
+    return SessionUser(id=parsed_user_id, email=email, is_admin=bool(is_admin))
+
+
+def set_session_user(
+    request: Request,
+    *,
+    user_id: int,
+    email: str,
+    is_admin: bool,
+) -> None:
+    request.session[SESSION_USER_ID_KEY] = int(user_id)
+    request.session[SESSION_USER_EMAIL_KEY] = email
+    request.session[SESSION_USER_IS_ADMIN_KEY] = bool(is_admin)
+
+
+def clear_session_user(request: Request) -> None:
+    request.session.pop(SESSION_USER_ID_KEY, None)
+    request.session.pop(SESSION_USER_EMAIL_KEY, None)
+    request.session.pop(SESSION_USER_IS_ADMIN_KEY, None)