Add backend support for users

backend/auth.py

@@ -0,0 +1,67 @@
+from datetime import datetime, timedelta
+from passlib.context import CryptContext
+from jose import JWTError, jwt
+import os
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from model import User, SessionLocal
+
+# JWT settings
+SECRET_KEY = os.getenv("SECRET_KEY", "")
+ALGORITHM = "HS256"
+ACCESS_TOKEN_EXPIRE_MINUTES = 60
+
+if SECRET_KEY == "":
+    raise ValueError("SECRET_KEY environment variable is not set")
+
+pwd_context = CryptContext(schemes=["argon2"], deprecated="auto")
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl="login")
+
+
+def verify_password(plain_password, hashed_password):
+    return pwd_context.verify(plain_password, hashed_password)
+
+
+def get_password_hash(password):
+    return pwd_context.hash(password)
+
+
+def create_access_token(data: dict, expires_delta: timedelta | None = None):
+    to_encode = data.copy()
+    expire = datetime.utcnow() + (
+        expires_delta or timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
+    )
+    to_encode.update({"exp": expire})
+    return jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
+
+
+def get_user(db, username: str):
+    return db.query(User).filter(User.username == username).first()
+
+
+def authenticate_user(db, username: str, password: str):
+    user = get_user(db, username)
+    if not user or not verify_password(password, user.password_hash):
+        return None
+    return user
+
+
+def get_current_user(token: str = Depends(oauth2_scheme)):
+    db = SessionLocal()
+    credentials_exception = HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Could not validate credentials",
+        headers={"WWW-Authenticate": "Bearer"},
+    )
+    try:
+        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
+        username: str | None = payload.get("sub")
+        if username is None:
+            raise credentials_exception
+    except JWTError:
+        raise credentials_exception
+    user = get_user(db, username)
+    db.close()
+    if user is None:
+        raise credentials_exception
+    return user