"""灵台引擎薄封装（Python 宿主接入，ADR-016）。

- 懒初始化进程级单例；初始化或调用失败一律抛 LingtaiUnavailable，
  由调用方 fail closed（禁止在宿主内用第二实现降级）。
- 仅做类型转换与错误映射，不缓存权威状态、不复制业务语义。
"""

import json
import threading
from typing import Any

import lingtai

_lock = threading.Lock()
_engine: lingtai.LingtaiEngine | None = None


class LingtaiUnavailable(RuntimeError):
    """引擎缺失、初始化失败或调用失败：依赖方必须显式失败。"""


def get_engine() -> lingtai.LingtaiEngine:
    global _engine
    with _lock:
        if _engine is None:
            try:
                _engine = lingtai.LingtaiEngine()
            except Exception as exc:  # nanobind LingtaiError 等
                raise LingtaiUnavailable(f"灵台引擎初始化失败：{exc}") from exc
        return _engine


def reset_engine() -> None:
    """测试辅助：丢弃单例，下次访问重新初始化。"""
    global _engine
    with _lock:
        _engine = None


def transform_markdown(text: str) -> dict[str, Any]:
    """Markdown → canonical ContentBlock（dict：parser_version + blocks）。"""
    try:
        engine = get_engine()
    except LingtaiUnavailable:
        raise
    try:
        raw = engine.transform_markdown(text)
    except Exception as exc:
        raise LingtaiUnavailable(f"灵台引擎调用失败：{exc}") from exc
    parsed: dict[str, Any] = json.loads(raw)
    for block in parsed["blocks"]:
        block.setdefault("id", None)
    return parsed


def transform_version() -> str:
    return str(lingtai.transform_version())