refactor and set up authentication

app/routers/user.py

@@ -0,0 +1,146 @@
+from datetime import datetime, timedelta, timezone
+from typing import Annotated
+
+from fastapi import Depends, APIRouter, HTTPException, Security, status
+from fastapi.security import OAuth2PasswordBearer, OAuth2PasswordRequestForm, SecurityScopes
+from jose import JWTError, jwt
+from passlib.context import CryptContext
+from pydantic import BaseModel, ValidationError
+
+from app.secrets import SECRET_KEY, fake_users_db
+# to get a string like this run:
+# openssl rand -hex 32
+
+ALGORITHM = "HS256"
+ACCESS_TOKEN_EXPIRE_MINUTES = 30
+
+
+class Token(BaseModel):
+    access_token: str
+    token_type: str
+
+
+class TokenData(BaseModel):
+    username: str | None = None
+    scopes: list[str] = []
+
+
+class User(BaseModel):
+    username: str
+    email: str | None = None
+    full_name: str | None = None
+    disabled: bool | None = None
+
+
+class UserInDB(User):
+    hashed_password: str
+    scopes: list[str] = []
+
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+oauth2_scheme = OAuth2PasswordBearer(
+    tokenUrl="user/token",
+    scopes={
+        "admin": "Perform admin actions."
+    }
+)
+
+router = APIRouter(
+    prefix="/user"
+)
+
+
+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 get_user(db, username: str):
+    if username in db:
+        user_dict = db[username]
+        return UserInDB(**user_dict)
+
+
+def authenticate_user(fake_db, username: str, password: str):
+    user = get_user(fake_db, username)
+    if not user:
+        return False
+    if not verify_password(password, user.hashed_password):
+        return False
+    return user
+
+
+def create_access_token(data: dict, expires_delta: timedelta | None = None):
+    to_encode = data.copy()
+    if expires_delta:
+        expire = datetime.now(timezone.utc) + expires_delta
+    else:
+        expire = datetime.now(timezone.utc) + timedelta(minutes=15)
+    to_encode.update({"exp": expire})
+    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
+    return encoded_jwt
+
+
+async def get_current_user(
+    security_scopes: SecurityScopes, token: Annotated[str, Depends(oauth2_scheme)]
+):
+    if security_scopes.scopes:
+        authenticate_value = f'Bearer scope="{security_scopes.scope_str}"'
+    else:
+        authenticate_value = "Bearer"
+    credentials_exception = HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Could not validate credentials",
+        headers={"WWW-Authenticate": authenticate_value},
+    )
+    try:
+        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
+        username: str = payload.get("sub")  # type: ignore
+        if username is None:
+            raise credentials_exception
+        token_scopes = payload.get("scopes", [])
+        token_data = TokenData(scopes=token_scopes, username=username)
+    except (JWTError, ValidationError):
+        raise credentials_exception
+    user = get_user(fake_users_db, username=token_data.username or "")
+    if user is None:
+        raise credentials_exception
+    for scope in security_scopes.scopes:
+        if scope not in token_data.scopes:
+            raise HTTPException(
+                status_code=status.HTTP_401_UNAUTHORIZED,
+                detail="Not enough permissions",
+                headers={"WWW-Authenticate": authenticate_value},
+            )
+    return user
+
+
+async def get_current_active_user(
+    current_user: Annotated[User, Security(get_current_user, scopes=["me"])],
+):
+    if current_user.disabled:
+        raise HTTPException(status_code=400, detail="Inactive user")
+    return current_user
+
+
+@router.post("/token")
+async def login_for_access_token(
+    form_data: Annotated[OAuth2PasswordRequestForm, Depends()],
+) -> Token:
+    user = authenticate_user(
+        fake_users_db, form_data.username, form_data.password)
+    if not user:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Incorrect username or password",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
+    access_token = create_access_token(
+        data={"sub": user.username, "scopes": user.scopes}, expires_delta=access_token_expires
+    )
+    return Token(access_token=access_token, token_type="bearer")