import os
from datetime import datetime, timedelta, timezone
from typing import Optional, Dict, Any

from jose import jwt, JWTError
from passlib.context import CryptContext
from fastapi import HTTPException, status, Depends
from fastapi.security import OAuth2PasswordBearer


# =========================================================
# ENV CONFIG
# =========================================================

SECRET_KEY = os.getenv("SECRET_KEY")

if not SECRET_KEY:
    raise RuntimeError("SECRET_KEY environment variable missing")

ALGORITHM = os.getenv("ALGORITHM", "HS256")

ACCESS_TOKEN_EXPIRE_MINUTES = int(
    os.getenv("ACCESS_TOKEN_EXPIRE_MINUTES", "1440")
)


# =========================================================
# PASSWORD HASHING
# =========================================================
# IMPORTANT:
# pbkdf2_sha256 avoids:
# - bcrypt crashes
# - bcrypt native dependency issues
# - 72-byte limits
# - passlib backend bugs
# =========================================================

pwd_context = CryptContext(
    schemes=["pbkdf2_sha256"],
    deprecated="auto",
)


def hash_password(password: str) -> str:

    if not password:
        raise ValueError("Password required")

    if len(password) < 8:
        raise ValueError("Password too short")

    return pwd_context.hash(password)


def verify_password(
    plain_password: str,
    hashed_password: str,
) -> bool:

    try:
        return pwd_context.verify(
            plain_password,
            hashed_password,
        )
    except Exception:
        return False


# =========================================================
# JWT
# =========================================================

def create_access_token(
    data: Dict[str, Any],
    expires_delta: Optional[timedelta] = None,
) -> str:

    to_encode = data.copy()

    expire = datetime.now(timezone.utc) + (
        expires_delta
        if expires_delta
        else timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    )

    to_encode.update({"exp": expire})

    return jwt.encode(
        to_encode,
        SECRET_KEY,
        algorithm=ALGORITHM,
    )


def decode_token(token: str):

    try:
        return jwt.decode(
            token,
            SECRET_KEY,
            algorithms=[ALGORITHM],
        )

    except JWTError:

        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid token",
            headers={"WWW-Authenticate": "Bearer"},
        )


# =========================================================
# AUTH DEPENDENCY
# =========================================================

oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl="/api/auth/login"
)


def get_current_user(
    token: str = Depends(oauth2_scheme)
):

    payload = decode_token(token)

    user_id = payload.get("sub")

    if not user_id:

        raise HTTPException(
            status_code=401,
            detail="Invalid authentication",
        )

    return payload