"""Authentication utilities for JWT token management."""

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

import bcrypt
import jwt
from jwt.exceptions import InvalidTokenError

# JWT configuration - get from environment or use defaults
SECRET_KEY = os.getenv("JWT_SECRET_KEY", "your-secret-key-change-in-production")
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = int(os.getenv("JWT_ACCESS_TOKEN_EXPIRE_MINUTES", "1440"))  # 24 hours default


# ---------------------------------------------------------------------------
# Password hashing and verification
# ---------------------------------------------------------------------------

def hash_password(plain_password: str) -> str:
    """Hash a plain text password using bcrypt.

    Args:
        plain_password: Plain text password to hash

    Returns:
        bcrypt hash string
    """
    return bcrypt.hashpw(plain_password.encode("utf-8"), bcrypt.gensalt()).decode("utf-8")


def verify_password(plain_password: str, hashed_password: str) -> bool:
    """Verify a plain text password against a bcrypt hash.

    Args:
        plain_password: Plain text password to verify
        hashed_password: bcrypt hash from the database

    Returns:
        True if password matches, False otherwise
    """
    return bcrypt.checkpw(plain_password.encode("utf-8"), hashed_password.encode("utf-8"))


# ---------------------------------------------------------------------------
# JWT token management
# ---------------------------------------------------------------------------

def create_access_token(data: dict, expires_delta: Optional[timedelta] = None) -> str:
    """Create a JWT access token.

    Args:
        data: Payload data to encode in token (typically {"sub": username})
        expires_delta: Optional custom expiration time

    Returns:
        Encoded JWT token string
    """
    to_encode = data.copy()

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

    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)

    return encoded_jwt


def decode_access_token(token: str) -> Optional[dict]:
    """Decode and verify a JWT access token.

    Args:
        token: JWT token string

    Returns:
        Decoded token payload if valid, None if invalid or expired
    """
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        return payload
    except InvalidTokenError:
        return None


def get_username_from_token(token: str) -> Optional[str]:
    """Extract username from JWT token.

    Args:
        token: JWT token string

    Returns:
        Username if token is valid, None otherwise
    """
    payload = decode_access_token(token)
    if payload:
        return payload.get("sub")
    return None