"""Lightweight server-side rate limiter (no external deps).

Per-key (user/IP + action) sliding-window counter, persisted to disk so restarts
don't fully reset abuse protection. In-memory fast path + on-disk snapshot.
"""
from __future__ import annotations

import json
import os
import threading
import time

from ..config import Config

_lock = threading.Lock()
_mem: dict[str, list[float]] = {}  # key -> list of recent timestamps


def _key(action: str, ident: str) -> str:
    return f"{action}:{ident}"


def _load():
    p = Config.DATA_DIR / "ratelimit.json"
    try:
        if p.exists():
            with open(p, encoding="utf-8") as fh:
                return json.load(fh)
    except Exception:
        pass
    return {}


def _save():
    try:
        p = Config.DATA_DIR / "ratelimit.json"
        p.parent.mkdir(parents=True, exist_ok=True)
        tmp = p.with_suffix(".json.tmp")
        with open(tmp, "w", encoding="utf-8") as fh:
            json.dump(_mem, fh)
        os.replace(tmp, p)
    except Exception:
        pass


def check(action: str, ident: str, *, limit: int, window: int) -> bool:
    """Return True if allowed; False if the limit in `window` seconds was exceeded."""
    key = _key(action, ident)
    now = time.time()
    with _lock:
        rec = list(_mem.get(key) or _load().get(key) or [])
        rec = [t for t in rec if now - t < window]
        if len(rec) >= limit:
            _mem[key] = rec
            return False
        rec.append(now)
        _mem[key] = rec
    # opportunistically persist (bounded writes)
    try:
        if int(now) % 5 == 0:
            _save()
    except Exception:
        pass
    return True