from datetime import timedelta
from fastapi import APIRouter, Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer, OAuth2PasswordRequestForm
from sqlalchemy.orm import Session
from jose import JWTError, jwt

from core.database import get_db
from core.security import (
    verify_password,
    get_password_hash,
    create_access_token,
    SECRET_KEY,
    ALGORITHM,
    ACCESS_TOKEN_EXPIRE_MINUTES
)
from models.user import User, UserRole
from schemas.user import UserCreate, UserResponse, Token

router = APIRouter(prefix="/auth", tags=["auth"])
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="auth/login")

def get_current_user(token: str = Depends(oauth2_scheme), db: Session = Depends(get_db)) -> 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])
        email: str = payload.get("sub")
        if email is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception
    
    user = db.query(User).filter(User.email == email).first()
    if user is None or not user.is_active:
        raise credentials_exception
    return user

def get_current_admin(current_user: User = Depends(get_current_user)) -> User:
    if current_user.role != UserRole.admin:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Operation permitted only for administrators"
        )
    return current_user

@router.post("/login", response_model=Token)
def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends(), 
    db: Session = Depends(get_db)
):
    user = db.query(User).filter(User.email == form_data.username).first()
    if not user or not verify_password(form_data.password, user.hashed_password):
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect email or password",
            headers={"WWW-Authenticate": "Bearer"},
        )
    
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.email, "role": user.role}, 
        expires_delta=access_token_expires
    )
    return {"access_token": access_token, "token_type": "bearer"}

@router.post("/register", response_model=UserResponse, status_code=status.HTTP_201_CREATED)
def register_user(
    user_in: UserCreate, 
    db: Session = Depends(get_db), 
    current_admin: User = Depends(get_current_admin)
):
    existing_user = db.query(User).filter(User.email == user_in.email).first()
    if existing_user:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Email already registered"
        )
    
    hashed_password = get_password_hash(user_in.password)
    db_user = User(
        email=user_in.email,
        hashed_password=hashed_password,
        role=user_in.role,
        is_active=True
    )
    db.add(db_user)
    db.commit()
    db.refresh(db_user)
    return db_user


@router.get("/me", response_model=UserResponse)
def read_users_me(current_user: User = Depends(get_current_user)):
    return current_user