feat: add token validation and auto-refresh functionality in frontend helpers

backend/app/routers/auth.py

@@ -4,6 +4,9 @@ import uuid
 from fastapi import APIRouter, HTTPException, status
 from jose import JWTError
 
+from fastapi import Depends
+
+from ..dependencies import get_current_user
 from ..models.auth import LoginRequest, RefreshRequest, RegisterRequest, TokenResponse
 from ..services.auth import (
     authenticate_user,
@@ -95,3 +98,11 @@ async def logout(body: RefreshRequest) -> None:
     jti = payload.get("jti", "")
     if jti:
         await revoke_refresh_token(jti)
+
+
+@router.get("/validate")
+async def validate(
+    current_user: dict = Depends(get_current_user),
+) -> dict:
+    """Return the token payload if the access token is valid."""
+    return current_user

frontend/app/helpers.py

@@ -76,6 +76,9 @@ def login_required(view):
     def wrapped(*args, **kwargs):
         if "access_token" not in session:
             return redirect(url_for("auth.login"))
+        # Validate, with auto-refresh on expiry
+        if not _validate_and_refresh():
+            return redirect(url_for("auth.login"))
         return view(*args, **kwargs)
     return wrapped
 
@@ -85,8 +88,61 @@ def admin_required(view):
     def wrapped(*args, **kwargs):
         if "access_token" not in session:
             return redirect(url_for("auth.login"))
+        if not _validate_and_refresh():
+            return redirect(url_for("auth.login"))
         if session.get("user_role") != "admin":
             flash("Admin access required.", "error")
             return redirect(url_for("dashboard.index"))
         return view(*args, **kwargs)
     return wrapped
+
+
+# ── Token validation & refresh ────────────────────────────────────────────
+
+def _validate_access_token(token: str) -> bool:
+    """Return True if the access token is still valid."""
+    try:
+        resp = _api("GET", "/auth/validate", token=token)
+        return resp.status_code == 200
+    except httpx.RequestError:
+        return False
+
+
+def _try_refresh() -> bool:
+    """Attempt to refresh an expired access token using the stored refresh token.
+
+    On success, updates session tokens in place. Returns True if a valid
+    access token exists after the attempt.
+    """
+    refresh_token = session.get("refresh_token")
+    if not refresh_token:
+        return False
+    try:
+        resp = _api("POST", "/auth/refresh",
+                    json={"refresh_token": refresh_token})
+    except httpx.RequestError:
+        return False
+    if resp.status_code != 200:
+        return False
+    data = resp.json()
+    session["access_token"] = data["access_token"]
+    session["refresh_token"] = data["refresh_token"]
+    return True
+
+
+def _validate_and_refresh() -> bool:
+    """Check access token validity; attempt refresh if expired.
+
+    Returns True if a valid session exists after the check.
+    """
+    token = session.get("access_token")
+    if not token:
+        return False
+    if _validate_access_token(token):
+        return True
+    # Access token expired — try to refresh
+    if _try_refresh():
+        return True
+    # Both tokens are dead — clear session
+    session.clear()
+    return False