import hashlib
import re
from datetime import datetime, timedelta
from typing import Optional

from fastapi import Cookie, Depends, Header, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt
from sqlmodel import Session, select

from app.config import settings

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/v1/auth/login")

ALGORITHM = "HS256"


def create_access_token(subject: str) -> str:
    expire = datetime.utcnow() + timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
    return jwt.encode({"sub": subject, "exp": expire}, settings.SECRET_KEY, algorithm=ALGORITHM)


def hash_token(token: str) -> str:
    return hashlib.sha256(token.encode()).hexdigest()


def _validate_token(token: str) -> str:
    """Validate JWT and return subject, or raise 401."""
    try:
        payload = jwt.decode(token, settings.SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED)
        return username
    except JWTError:
        pass

    # Fallback: check API token
    from app.db import get_session
    from app.models.models import APIToken

    token_hash = hash_token(token)
    with next(get_session()) as session:
        api_token = session.exec(
            select(APIToken).where(
                APIToken.token_hash == token_hash,
                APIToken.is_active == True,
            )
        ).first()
        if api_token:
            if api_token.expires_at and api_token.expires_at < datetime.utcnow():
                raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Token expired")
            return f"api:{api_token.name}"

    raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED)


def get_current_user_cookie_or_bearer(
    authorization: Optional[str] = Header(default=None),
    ws_token: Optional[str] = Cookie(default=None),
) -> str:
    """Accepts httpOnly cookie (SPA) or Bearer token (API clients / n8n)."""
    token: Optional[str] = None
    if authorization and authorization.lower().startswith("bearer "):
        token = authorization.split(" ", 1)[1].strip()
    elif ws_token:
        token = ws_token
    if not token:
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED)
    return _validate_token(token)


def get_current_user(
    authorization: Optional[str] = Header(default=None),
    ws_token: Optional[str] = Cookie(default=None),
) -> str:
    """SPA cookie or Bearer token. Single dependency for all v1 endpoints."""
    return get_current_user_cookie_or_bearer(authorization, ws_token)