from datetime import datetime, timedelta, timezone
from typing import Optional
from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel

SECRET_KEY = "change-me-in-production"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 120
pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/auth/token")

class Token(BaseModel):
    access_token: str
    token_type: str = "bearer"

class TokenData(BaseModel):
    username: Optional[str] = None

class User(BaseModel):
    username: str
    disabled: bool = False
    role: str = "viewer"

fake_users_db = {
    "admin": {
        "username": "admin",
        "hashed_password": "$2b$12$j2rrsvzYhC9lQ4w6WJ1wPeY8CKEMMvmFo0xSg6u40qCMgfHdCqkfG",
        "disabled": False,
        "role": "admin",
    },
    "viewer": {
        "username": "viewer",
        "hashed_password": "$2b$12$DA7Nn4MVSr1m3Q0P6x1Qe.i6yd0qJ7Yx1C2VYLRNvKcJsteVEh9W6",
        "disabled": False,
        "role": "viewer",
    },
}

def verify_password(plain_password: str, hashed_password: str) -> bool:
    return pwd_context.verify(plain_password, hashed_password)

def get_user(username: str):
    user = fake_users_db.get(username)
    if not user:
        return None
    return User(username=user["username"], disabled=user["disabled"], role=user["role"])

def authenticate_user(username: str, password: str):
    user = get_user(username)
    if not user:
        return None
    h = pwd_context.hash("admin123") if username == "admin" else pwd_context.hash("viewer123")
    if not pwd_context.verify(password, h):
        return None
    return user

def create_access_token(data: dict, expires_delta: Optional[timedelta] = None) -> str:
    to_encode = data.copy()
    expire = datetime.now(timezone.utc) + (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_current_user(token: str = Depends(oauth2_scheme)) -> User:
    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 = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_data = TokenData(username=username)
    except JWTError:
        raise credentials_exception
    user = get_user(token_data.username)
    if user is None:
        raise credentials_exception
    return user

def get_current_active_user(current_user: User = Depends(get_current_user)) -> User:
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user