"""Idempotency for autonomous mode: don't create the same event twice.

As more messages stream into a chat, re-running the agent over a rolling window
re-surfaces events already captured. ``filter_new`` returns only events not seen
before, keyed by normalized title + minute-rounded start. Durable JSON store
mirrors ``server/impact.py`` (env path + lock; no DB — local-first).
"""
from __future__ import annotations

import json
import os
import threading
from pathlib import Path

from dateutil import parser as dtparser

from .schema import Event

_lock = threading.Lock()


def _path() -> Path:
    return Path(os.environ.get("DEDUP_PATH", "/tmp/agent_seen.json"))


def event_key(ev: Event) -> str:
    """Normalized identity: lowercased title + start rounded to the minute.

    Conservative by design — if the model rewords a title between messages we may
    miss a dedup (a duplicate event), which is safer than dropping a real event.
    """
    title = (ev.title or "").strip().lower()
    try:
        start = dtparser.isoparse(ev.start).replace(second=0, microsecond=0).isoformat()
    except (ValueError, TypeError):
        start = (ev.start or "").strip()
    return f"{title}|{start}"


def _load() -> list[str]:
    try:
        return json.loads(_path().read_text())
    except Exception:  # noqa: BLE001  missing/corrupt -> start fresh
        return []


def filter_new(events: list[Event], record: bool = True) -> list[Event]:
    """Return only events whose key hasn't been recorded.

    ``record=False`` filters WITHOUT persisting — callers delivering the events
    somewhere fallible (e.g. a calendar push) should filter first and
    ``mark_seen`` only after delivery succeeds; otherwise a transient failure
    permanently swallows the events ("seen" but never delivered)."""
    with _lock:
        seen = set(_load())
        fresh = []
        for ev in events:
            k = event_key(ev)
            if k in seen:
                continue
            seen.add(k)
            fresh.append(ev)
        if fresh and record:
            _path().write_text(json.dumps(sorted(seen), indent=2))
        return fresh


def mark_seen(events: list[Event]) -> None:
    """Persist the keys of successfully delivered events."""
    if not events:
        return
    with _lock:
        seen = set(_load())
        seen.update(event_key(ev) for ev in events)
        _path().write_text(json.dumps(sorted(seen), indent=2))


def reset() -> None:
    """Drop the seen-set (test helper)."""
    with _lock:
        try:
            _path().unlink()
        except FileNotFoundError:
            pass