from fastapi import APIRouter, Depends, HTTPException, status
from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
from sqlalchemy.orm import Session
from jose import JWTError, jwt
from app.db.session import get_db
from app.models.user import User
from app.schemas.user import UserCreate, UserLogin, User as UserSchema
from app.core.security import (
    verify_password, 
    get_password_hash, 
    create_access_token,
    SECRET_KEY,
    ALGORITHM
)

router = APIRouter()
security = HTTPBearer()


def get_user_by_email(db: Session, email: str):
    return db.query(User).filter(User.email == email).first()


def create_user(db: Session, user: UserCreate):
    hashed_password = get_password_hash(user.password)
    db_user = User(
        email=user.email,
        hashed_password=hashed_password,
        full_name=user.full_name,
    )
    db.add(db_user)
    db.commit()
    db.refresh(db_user)
    return db_user


def authenticate_user(db: Session, email: str, password: str):
    user = get_user_by_email(db, email)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def get_current_user(
    credentials: HTTPAuthorizationCredentials = Depends(security),
    db: Session = Depends(get_db)
):
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(credentials.credentials, SECRET_KEY, algorithms=[ALGORITHM])
        user_id: int = payload.get("sub")
        if user_id is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception
    
    user = db.query(User).filter(User.id == user_id).first()
    if user is None:
        raise credentials_exception
    return user


@router.post("/register", response_model=UserSchema)
def register(user: UserCreate, db: Session = Depends(get_db)):
    db_user = get_user_by_email(db, email=user.email)
    if db_user:
        raise HTTPException(
            status_code=400,
            detail="Email already registered"
        )
    return create_user(db=db, user=user)


@router.post("/login")
def login(user_credentials: UserLogin, db: Session = Depends(get_db)):
    user = authenticate_user(db, user_credentials.email, user_credentials.password)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect email or password",
            headers={"WWW-Authenticate": "Bearer"},
        )
    access_token = create_access_token(subject=user.id)
    return {"access_token": access_token, "token_type": "bearer"}


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