"""TTL-aware cache for mDNS resolutions. JSON-backed for portability."""
import json
import os
import time
from pathlib import Path

CACHE_PATH = Path(os.environ.get(
    "MDNS_CACHE_PATH",
    Path.home() / ".cache" / "mdns" / "hosts.json",
))


def _load() -> dict:
    if not CACHE_PATH.exists():
        return {}
    try:
        return json.loads(CACHE_PATH.read_text())
    except Exception:
        return {}


def _save(data: dict) -> None:
    CACHE_PATH.parent.mkdir(parents=True, exist_ok=True)
    tmp = CACHE_PATH.with_suffix(".tmp")
    tmp.write_text(json.dumps(data, indent=2, sort_keys=True))
    tmp.replace(CACHE_PATH)


def get(host: str, family: str = "v4") -> str | None:
    """Return IP if fresh, None if missing or expired."""
    entry = _load().get(f"{host}|{family}")
    if not entry:
        return None
    if entry.get("expires", 0) < time.time():
        return None
    return entry.get("ip")


def get_stale(host: str, family: str = "v4") -> str | None:
    """Return IP even if expired (last-resort fallback)."""
    entry = _load().get(f"{host}|{family}")
    return entry.get("ip") if entry else None


def put(host: str, ip: str, family: str = "v4", ttl: int = 120) -> None:
    data = _load()
    ttl = max(30, min(ttl, 3600))
    data[f"{host}|{family}"] = {
        "ip": ip,
        "ttl": ttl,
        "expires": time.time() + ttl,
        "updated": time.time(),
    }
    _save(data)


def clear(host: str | None = None) -> int:
    """Clear entries. Returns number of entries removed."""
    if host is None:
        n = len(_load())
        if CACHE_PATH.exists():
            CACHE_PATH.unlink()
        return n
    data = _load()
    removed = [k for k in list(data) if k.split("|")[0] == host]
    for k in removed:
        data.pop(k)
    _save(data)
    return len(removed)


def all_entries() -> dict:
    return _load()