external_demand/app/gap_script_demand/llm_json.py

"""LLM 回复 JSON 解析工具。"""

from __future__ import annotations

import json
import re
from typing import Any

from app.gap_script_demand.exceptions import GapScriptDemandError


def strip_markdown_fence(text: str) -> str:
    raw = text.strip()
    if not raw.startswith("```"):
        return raw
    raw = re.sub(r"^```(?:json)?\s*", "", raw, flags=re.IGNORECASE)
    raw = re.sub(r"\s*```\s*$", "", raw)
    return raw.strip()


def extract_json_object(text: str) -> dict[str, Any]:
    """从 LLM 回复中提取第一个 JSON 对象（容忍尾部多余文字）。"""
    raw = strip_markdown_fence(text)
    decoder = json.JSONDecoder()

    def _try_decode(candidate: str) -> dict[str, Any] | None:
        stripped = candidate.strip()
        if not stripped:
            return None
        try:
            parsed = json.loads(stripped)
            if isinstance(parsed, dict):
                return parsed
        except json.JSONDecodeError:
            pass
        try:
            parsed, _end = decoder.raw_decode(stripped)
            if isinstance(parsed, dict):
                return parsed
        except json.JSONDecodeError:
            pass
        return None

    direct = _try_decode(raw)
    if direct is not None:
        return direct

    start = 0
    while True:
        start = raw.find("{", start)
        if start == -1:
            break
        decoded = _try_decode(raw[start:])
        if decoded is not None:
            return decoded
        start += 1

    raise GapScriptDemandError("llm output is not json object")