# src/metrics.py
"""Lightweight metrics collection: counters and timers to JSON file."""

import json
import os
import time

from .common import LOG_DIR

METRICS_FILE = os.path.join(LOG_DIR, "metrics.json")


class Metrics:
    def __init__(self) -> None:
        self._counters: dict[str, int] = {}
        self._timers: dict[str, float] = {}

    def inc(self, key: str, n: int = 1) -> None:
        self._counters[key] = self._counters.get(key, 0) + n

    def observe(self, key: str, value: float) -> None:
        # Store last observed value
        self._timers[key] = float(value)

    def dump(self) -> None:
        os.makedirs(LOG_DIR, exist_ok=True)
        payload = {
            "ts": time.time(),
            "counters": self._counters,
            "timers": self._timers,
        }
        try:
            with open(METRICS_FILE, "w", encoding="utf-8") as f:
                json.dump(payload, f, ensure_ascii=False, indent=2)
        except Exception:
            # Metrics should never crash app
            pass


metrics = Metrics()