import json
import math

from fastapi.responses import JSONResponse


def _sanitize(obj):
    """Replace NaN/Infinity with None so every payload remains valid JSON."""
    if isinstance(obj, float):
        if math.isnan(obj) or math.isinf(obj):
            return None
    if isinstance(obj, dict):
        return {k: _sanitize(v) for k, v in obj.items()}
    if isinstance(obj, list):
        return [_sanitize(i) for i in obj]
    return obj


class SafeJSONResponse(JSONResponse):
    """JSONResponse variant that normalizes non-JSON float values."""

    def render(self, content) -> bytes:
        return json.dumps(_sanitize(content), ensure_ascii=False).encode("utf-8")