feat: add JWT creation, decoding and cookie helpers

app/core/auth.py

@@ -0,0 +1,47 @@
+from datetime import datetime, timedelta, timezone
+from typing import Optional
+
+from fastapi import Request, Response
+from jose import JWTError, jwt
+
+from app.core.config import get_settings
+
+settings = get_settings()
+
+COOKIE_NAME = "access_token"
+ALGORITHM = "HS256"
+TOKEN_EXPIRE_HOURS = 8
+
+
+def create_access_token(username: str, is_admin: bool) -> str:
+    expire = datetime.now(timezone.utc) + timedelta(hours=TOKEN_EXPIRE_HOURS)
+    return jwt.encode(
+        {"sub": username, "is_admin": is_admin, "exp": expire},
+        settings.SECRET_KEY,
+        algorithm=ALGORITHM,
+    )
+
+
+def decode_token(token: str) -> Optional[dict]:
+    try:
+        return jwt.decode(token, settings.SECRET_KEY, algorithms=[ALGORITHM])
+    except JWTError:
+        return None
+
+
+def get_token_from_request(request: Request) -> Optional[str]:
+    return request.cookies.get(COOKIE_NAME)
+
+
+def set_auth_cookie(response: Response, token: str) -> None:
+    response.set_cookie(
+        key=COOKIE_NAME,
+        value=token,
+        httponly=True,
+        samesite="lax",
+        secure=settings.APP_ENV == "production",
+    )
+
+
+def clear_auth_cookie(response: Response) -> None:
+    response.delete_cookie(key=COOKIE_NAME, httponly=True, samesite="lax")

tests/test_core_auth.py

@@ -0,0 +1,27 @@
+from app.core.auth import COOKIE_NAME, create_access_token, decode_token
+
+
+def test_create_and_decode_token():
+    token = create_access_token(username="alice", is_admin=False)
+    payload = decode_token(token)
+    assert payload is not None
+    assert payload["sub"] == "alice"
+    assert payload["is_admin"] is False
+
+
+def test_admin_claim():
+    token = create_access_token(username="admin", is_admin=True)
+    assert decode_token(token)["is_admin"] is True
+
+
+def test_decode_invalid_token():
+    assert decode_token("not.a.valid.token") is None
+
+
+def test_decode_tampered_token():
+    token = create_access_token(username="alice", is_admin=False)
+    assert decode_token(token[:-4] + "xxxx") is None
+
+
+def test_cookie_name():
+    assert COOKIE_NAME == "access_token"