#!/usr/bin/env python3
"""Bounded-memory stream helpers for the Hermes SCM broker."""

from __future__ import annotations

import tempfile
import time
from typing import BinaryIO

from gitea_api_policy import PolicyError


def spool_response(
    response,
    maximum: int,
    forbidden: tuple[bytes, ...],
    *,
    memory_limit: int,
    chunk_size: int,
    deadline_seconds: float,
) -> tuple[BinaryIO, int]:
    """Spool an upstream response to disk while scanning chunk boundaries."""
    spool = tempfile.SpooledTemporaryFile(max_size=memory_limit, dir="/tmp")
    carry = b""
    total = 0
    deadline = time.monotonic() + deadline_seconds
    try:
        while True:
            remaining = deadline - time.monotonic()
            if remaining <= 0:
                raise PolicyError("SCM upstream response deadline exceeded")
            raw = getattr(getattr(response, "fp", None), "raw", None)
            sock = getattr(raw, "_sock", raw)
            if hasattr(sock, "settimeout"):
                sock.settimeout(remaining)
            chunk = response.read(chunk_size)
            if not chunk:
                break
            total += len(chunk)
            if total > maximum:
                raise PolicyError("SCM upstream response exceeds the safe size limit")
            candidate = carry + chunk
            if any(value in candidate for value in forbidden):
                raise PolicyError(
                    "Git upstream response contains runtime credential material"
                )
            width = max(len(value) for value in forbidden) - 1
            carry = candidate[-width:] if width else b""
            spool.write(chunk)
        spool.seek(0)
        return spool, total
    except Exception:
        spool.close()
        raise