"""Decide whether a request body is too large to read.

Nothing else caps request size: uvicorn has no default, and the handlers read
the whole body before looking at it.
"""

from collections.abc import Mapping

MAX_BYTES = 512 * 1024      # far more than a 10-message history or 5 000-char TTS text
MAX_FRAME_BYTES = 256 * 1024  # a single websocket frame; mic frames are a few KB

_BODY_METHODS = frozenset({"POST", "PUT", "PATCH"})


def is_too_large(method: str, headers: Mapping[str, str]) -> bool:
    """True when the request should be refused before its body is read.

    A declared length over the cap is refused, and so is a body with no
    declared length at all — that is a chunked upload, which would otherwise
    stream past the check unmeasured. No browser sends chunked JSON here.

    A request with neither header carries no body (a bodyless POST) and is
    fine: rejecting those broke /api/benchmark the first time round.
    """
    if method.upper() not in _BODY_METHODS:
        return False
    declared = headers.get("content-length")
    if declared is None:
        return bool(headers.get("transfer-encoding"))
    if not declared.isdigit():
        return True
    return int(declared) > MAX_BYTES