from datetime import datetime, timedelta, timezone
import os

import bcrypt
from jose import JWTError, jwt

# ── Config (override via environment variables) ───────────────────────────────
_raw_secret = os.getenv("JWT_SECRET_KEY", "")
if not _raw_secret:
    import warnings
    _raw_secret = "lms_dev_jwt_secret_change_in_production"
    warnings.warn(
        "JWT_SECRET_KEY is not set — using insecure default. "
        "Set it in .env before going to production.",
        RuntimeWarning,
        stacklevel=1,
    )
SECRET_KEY: str = _raw_secret
ALGORITHM: str = os.getenv("JWT_ALGORITHM", "HS256")
ACCESS_TOKEN_EXPIRE_MINUTES: int = int(
    os.getenv("ACCESS_TOKEN_EXPIRE_MINUTES", "60")
)

# ── Password hashing (use bcrypt directly — passlib has compat issues) ────────

def hash_password(plain: str) -> str:
    return bcrypt.hashpw(plain.encode(), bcrypt.gensalt()).decode()


def verify_password(plain: str, hashed: str) -> bool:
    return bcrypt.checkpw(plain.encode(), hashed.encode())


# ── JWT ───────────────────────────────────────────────────────────────────────

def create_access_token(user_id: int) -> str:
    expire = datetime.now(timezone.utc) + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    payload = {"sub": str(user_id), "exp": expire}
    return jwt.encode(payload, SECRET_KEY, algorithm=ALGORITHM)


def decode_access_token(token: str) -> int:
    """
    Decode the JWT and return the user_id (int).
    Raises JWTError on any validation failure.
    """
    payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
    sub = payload.get("sub")
    if sub is None:
        raise JWTError("Missing subject claim.")
    return int(sub)