from datetime import timedelta

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

from app.database import get_db
from app.schemas.user import User, UserCreate, Token, TokenData
from app.utils import (
    ACCESS_TOKEN_EXPIRE_MINUTES,
    ALGORITHM,
    SECRET_KEY,
    create_access_token,
    create_user,
    get_user,
    get_user_by_email,
    get_user_by_username,
    verify_password,
)

router = APIRouter(
    prefix="/users",
    tags=["users"],
)

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="users/token")


async def get_current_user(
    token: str = Depends(oauth2_scheme), db: Session = Depends(get_db)
):
    """Get the current user from the JWT token."""
    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_by_username(db, username=token_data.username)
    if user is None:
        raise credentials_exception
    return user


@router.post("/", response_model=User, status_code=status.HTTP_201_CREATED)
async def register_user(user: UserCreate, db: Session = Depends(get_db)):
    """Register a new user."""
    # Check if email already exists
    db_user = get_user_by_email(db, email=user.email)
    if db_user:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST, detail="Email already registered"
        )

    # Check if username already exists
    db_user = get_user_by_username(db, username=user.username)
    if db_user:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST, detail="Username already taken"
        )

    # Create user
    return create_user(db, user.email, user.username, user.password)


@router.post("/token", response_model=Token)
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends(), db: Session = Depends(get_db)
):
    """Get an access token from username and password."""
    user = get_user_by_username(db, username=form_data.username)
    if not user or not verify_password(form_data.password, user.hashed_password):
        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}, expires_delta=access_token_expires
    )
    return {"access_token": access_token, "token_type": "bearer"}


@router.get("/me", response_model=User)
async def read_users_me(current_user: User = Depends(get_current_user)):
    """Get the current authenticated user."""
    return current_user


@router.get("/{user_id}", response_model=User)
async def read_user(user_id: int, db: Session = Depends(get_db)):
    """Get a user by ID."""
    db_user = get_user(db, user_id=user_id)
    if db_user is None:
        raise HTTPException(status_code=404, detail="User not found")
    return db_user