"""
경량 모니터링 이벤트(JSONL) 기록 및 읽기 유틸
 - worker 스케일 업/다운
 - 세션 생성/회수
"""
from __future__ import annotations

import os
import time
import json
from typing import Dict, Any, List


LOG_DIR = "logs"
os.makedirs(LOG_DIR, exist_ok=True)

EVENT_LOG_PATH = os.path.join(LOG_DIR, "scale_events.jsonl")
MAX_BYTES = 10 * 1024 * 1024  # 10MB
BACKUP = 10


def _rotate_if_needed():
    try:
        if os.path.exists(EVENT_LOG_PATH) and os.path.getsize(EVENT_LOG_PATH) > MAX_BYTES:
            ts = time.strftime("%Y%m%d-%H%M%S")
            os.replace(EVENT_LOG_PATH, os.path.join(LOG_DIR, f"scale_events_{ts}.jsonl"))
            rotated = [os.path.join(LOG_DIR, f) for f in os.listdir(LOG_DIR) if f.startswith("scale_events_")]
            rotated.sort(key=lambda p: os.path.getmtime(p), reverse=True)
            for p in rotated[BACKUP:]:
                try:
                    os.remove(p)
                except Exception:
                    pass
    except Exception:
        pass


def append_event(event: Dict[str, Any]) -> None:
    try:
        _rotate_if_needed()
        if "timestamp" not in event:
            event["timestamp"] = time.time()
        with open(EVENT_LOG_PATH, "a", encoding="utf-8") as f:
            f.write(json.dumps(event, ensure_ascii=False) + "\n")
    except Exception:
        pass


def read_recent_events(limit: int = 300) -> List[Dict[str, Any]]:
    try:
        if not os.path.exists(EVENT_LOG_PATH):
            return []
        events: List[Dict[str, Any]] = []
        with open(EVENT_LOG_PATH, "r", encoding="utf-8") as f:
            # 간단히 끝에서 limit줄만 읽기 (파일이 크지 않다고 가정)
            lines = f.readlines()[-limit:]
        for line in lines:
            line = line.strip()
            if not line:
                continue
            try:
                events.append(json.loads(line))
            except Exception:
                continue
        return events
    except Exception:
        return []