from hashlib import sha256

_AUDIT_IDENTITY_DOMAIN = b"company-ai-platform:feishu-audit-identity:v1\0"


def feishu_audit_identity_hash(tenant_key: str, open_id: str) -> str:
    """Return the erasable pseudonymous subject used by pre-registration audits."""

    tenant_bytes = tenant_key.encode("utf-8")
    open_id_bytes = open_id.encode("utf-8")
    identity = b"".join(
        (
            len(tenant_bytes).to_bytes(4, "big"),
            tenant_bytes,
            len(open_id_bytes).to_bytes(4, "big"),
            open_id_bytes,
        )
    )
    digest = sha256(_AUDIT_IDENTITY_DOMAIN + identity).hexdigest()
    return f"feishu-identity-sha256-{digest}"