from dataclasses import dataclass
from hashlib import sha256

from fastapi import Request


@dataclass(frozen=True)
class AgentCredential:
    key_hash: str
    key_fingerprint: str


def hash_agent_key(token: str) -> str:
    return sha256(token.encode("utf-8")).hexdigest()


def fingerprint_from_hash(key_hash: str) -> str:
    return key_hash[:16]


def credential_from_token(token: str) -> AgentCredential:
    key_hash = hash_agent_key(token)
    return AgentCredential(key_hash=key_hash, key_fingerprint=fingerprint_from_hash(key_hash))


def get_agent_credential(request: Request) -> AgentCredential:
    cred = getattr(request.state, "agent_credential", None)
    if not isinstance(cred, AgentCredential):
        raise RuntimeError("agent credential missing")
    return cred