import os
import jwt
import datetime
import uuid
from fastapi import Request, HTTPException, Depends
from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
from src.utils.logger import setup_logger

logger = setup_logger("Auth")
security = HTTPBearer(auto_error=False)

# Default patient fallback is allowed only in development when explicitly enabled
DEFAULT_PATIENT_ID = os.getenv("DEFAULT_PATIENT_UUID")
DEV_ALLOW_DEFAULT_PATIENT = os.getenv("DEV_ALLOW_DEFAULT_PATIENT", "false").lower() in ("1", "true", "yes")


def get_current_user(credentials: HTTPAuthorizationCredentials = Depends(security)):
    """
    Verifies the Supabase JWT and returns the user ID (sub).
    """
    if not credentials:
        raise HTTPException(status_code=401, detail="Missing credentials")

    token = credentials.credentials
    jwt_secret = os.getenv("SUPABASE_JWT_SECRET")

    if not jwt_secret:
        logger.error("SUPABASE_JWT_SECRET not found in environment")
        raise HTTPException(status_code=500, detail="JWT secret missing")

    try:
        # Supabase uses HS256 for signing JWTs with the project secret
        payload = jwt.decode(token, jwt_secret, algorithms=["HS256"], audience="authenticated")
        user_id = payload.get("sub")
        if not user_id:
            raise HTTPException(status_code=401, detail="Invalid token: missing sub")
        return user_id
    except jwt.ExpiredSignatureError:
        raise HTTPException(status_code=401, detail="Token has expired")
    except jwt.InvalidTokenError as e:
        logger.warning(f"Invalid token: {e}")
        raise HTTPException(status_code=401, detail="Invalid token")


def get_active_user(credentials: HTTPAuthorizationCredentials = Depends(security)):
    """
    Returns the user ID from the token if valid.
    In development mode (DEV_ALLOW_DEFAULT_PATIENT) it falls back to DEFAULT_PATIENT_ID when no token provided.
    In production it will raise 401 for missing/invalid tokens.
    """
    if not credentials:
        if DEV_ALLOW_DEFAULT_PATIENT and DEFAULT_PATIENT_ID:
            logger.info("No credentials provided; falling back to DEFAULT_PATIENT_ID (dev mode)")
            return DEFAULT_PATIENT_ID
        raise HTTPException(status_code=401, detail="Missing credentials")

    try:
        return get_current_user(credentials)
    except HTTPException as e:
        # In dev mode we may still fall back
        if DEV_ALLOW_DEFAULT_PATIENT and DEFAULT_PATIENT_ID:
            logger.info("Invalid credentials; falling back to DEFAULT_PATIENT_ID (dev mode)")
            return DEFAULT_PATIENT_ID
        raise e


def create_dev_token(patient_id: str, expires_minutes: int = 60):
    """Create a development JWT signed with SUPABASE_JWT_SECRET for local dev/testing.

    The token uses `sub` to store the patient/user id and `aud` of 'authenticated' to match validation.
    """
    jwt_secret = os.getenv("SUPABASE_JWT_SECRET")
    if not jwt_secret:
        raise RuntimeError("SUPABASE_JWT_SECRET not set; cannot create token")

    now = datetime.datetime.utcnow()
    payload = {
        "sub": patient_id,
        "iat": now,
        "exp": now + datetime.timedelta(minutes=expires_minutes),
        "aud": "authenticated",
    }
    token = jwt.encode(payload, jwt_secret, algorithm="HS256")
    return token