from __future__ import annotations

from datetime import datetime, timezone
import json
from pathlib import Path
from typing import Any

from app.persistence import atomic_write_bytes

OTA_STATE_SCHEMA_VERSION = 1


def utc_now() -> str:
    return datetime.now(timezone.utc).isoformat(timespec="seconds").replace("+00:00", "Z")


def read_json(path: Path) -> dict[str, Any] | None:
    try:
        value = json.loads(Path(path).read_text(encoding="utf-8"))
    except (OSError, UnicodeError, json.JSONDecodeError):
        return None
    return value if isinstance(value, dict) else None


def write_json(path: Path, document: dict[str, Any]) -> None:
    atomic_write_bytes(
        Path(path),
        (json.dumps(document, ensure_ascii=False, indent=2, sort_keys=True) + "\n").encode("utf-8"),
    )


def read_last_result(data_root: Path) -> dict[str, Any] | None:
    document = read_json(Path(data_root) / "ota" / "state.json")
    if not document or document.get("schema_version") != OTA_STATE_SCHEMA_VERSION:
        return None
    result = document.get("last_result")
    return dict(result) if isinstance(result, dict) else None


def write_last_result(data_root: Path, result: dict[str, Any]) -> None:
    write_json(
        Path(data_root) / "ota" / "state.json",
        {"schema_version": OTA_STATE_SCHEMA_VERSION, "last_result": dict(result)},
    )