"""Stable JSON serialization helpers for v2 models."""

from __future__ import annotations

import json
from dataclasses import asdict, is_dataclass
from datetime import datetime
from pathlib import Path
from typing import Any, TypeVar

T = TypeVar("T")


def _normalize(obj: Any) -> Any:
    if obj is None or isinstance(obj, (str, int, float, bool)):
        return obj
    if isinstance(obj, datetime):
        return obj.isoformat()
    if isinstance(obj, Path):
        return str(obj).replace("\\", "/")
    if is_dataclass(obj) and not isinstance(obj, type):
        return {k: _normalize(v) for k, v in asdict(obj).items()}
    if isinstance(obj, dict):
        return {str(k): _normalize(v) for k, v in obj.items()}
    if isinstance(obj, (list, tuple)):
        return [_normalize(x) for x in obj]
    return str(obj)


def to_dict(obj: Any) -> dict[str, Any]:
    data = _normalize(obj)
    if not isinstance(data, dict):
        raise TypeError(f"expected dataclass/dict, got {type(obj)!r}")
    return data


def from_dict(cls: type[T], data: dict[str, Any]) -> T:
    """Best-effort dataclass reconstruction (ignores unknown keys)."""
    if not is_dataclass(cls):
        raise TypeError(f"{cls!r} is not a dataclass")
    import dataclasses

    fields = {f.name for f in dataclasses.fields(cls)}
    kwargs = {k: v for k, v in (data or {}).items() if k in fields}
    return cls(**kwargs)  # type: ignore[call-arg]


def dumps_json(obj: Any, *, indent: int = 2) -> str:
    return json.dumps(
        to_dict(obj) if is_dataclass(obj) and not isinstance(obj, type) else _normalize(obj),
        ensure_ascii=False,
        indent=indent,
        sort_keys=False,
    ) + "\n"


def write_model_json(path: Path, obj: Any) -> None:
    path = Path(path)
    path.parent.mkdir(parents=True, exist_ok=True)
    path.write_text(dumps_json(obj), encoding="utf-8")


def read_json(path: Path) -> Any:
    return json.loads(Path(path).read_text(encoding="utf-8"))