from __future__ import annotations

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


def now_iso() -> str:
    return datetime.now(timezone.utc).isoformat()


@dataclass(frozen=True)
class CachedSnapshot:
    provider_key: str
    updated_at: str
    data: dict[str, Any]


class SnapshotCache:
    def __init__(self, cache_dir: Path) -> None:
        self.cache_dir = cache_dir

    def path_for(self, provider_key: str) -> Path:
        return self.cache_dir / f"{provider_key}.json"

    def write(self, provider_key: str, data: dict[str, Any]) -> Path:
        self.cache_dir.mkdir(parents=True, exist_ok=True)
        payload = {
            "provider_key": provider_key,
            "updated_at": now_iso(),
            "data": data,
        }
        path = self.path_for(provider_key)
        path.write_text(json.dumps(payload, indent=2, ensure_ascii=False) + "\n", encoding="utf-8")
        return path

    def read(self, provider_key: str) -> CachedSnapshot | None:
        path = self.path_for(provider_key)
        if not path.exists():
            return None
        payload = json.loads(path.read_text(encoding="utf-8"))
        return CachedSnapshot(
            provider_key=payload["provider_key"],
            updated_at=payload["updated_at"],
            data=payload["data"],
        )