import secrets
import hashlib
from datetime import datetime, timedelta, timezone
from typing import Optional, Any
import jwt
import bcrypt
from app.core.config import settings

def get_password_hash(password: str) -> str:
    """Hashes a password with bcrypt."""
    salt = bcrypt.gensalt()
    return bcrypt.hashpw(password.encode("utf-8"), salt).decode("utf-8")

def verify_password(plain_password: str, hashed_password: str) -> bool:
    """Verifies a plain password against a bcrypt hash."""
    try:
        return bcrypt.checkpw(plain_password.encode("utf-8"), hashed_password.encode("utf-8"))
    except Exception:
        return False

def create_access_token(subject: Any, role: str = "ADMIN", expires_delta: Optional[timedelta] = None) -> str:
    """Creates a JWT access token for authentication."""
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
    
    to_encode = {
        "exp": expire,
        "sub": str(subject),
        "role": role,
        "iat": datetime.now(timezone.utc)
    }
    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
    return encoded_jwt

def decode_access_token(token: str) -> Optional[dict]:
    """Decodes and validates a JWT token."""
    try:
        payload = jwt.decode(token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM])
        return payload
    except Exception:
        return None

def generate_registration_code() -> str:
    """Generates an agent registration code formatted as OED-XXXX-XXXX."""
    part1 = secrets.token_hex(2).upper()
    part2 = secrets.token_hex(2).upper()
    return f"OED-{part1}-{part2}"

def generate_device_token() -> str:
    """Generates a high-entropy secret token for an agent device."""
    return f"oed_sec_{secrets.token_urlsafe(32)}"

def hash_token(token: str) -> str:
    """Returns the SHA-256 hex digest of a token for secure database lookup."""
    return hashlib.sha256(token.encode("utf-8")).hexdigest()