from __future__ import annotations

import time
from collections import defaultdict
from typing import Dict


class MetricsRecorder:
    """Lightweight in-process metrics aggregator."""

    def __init__(self) -> None:
        self.counters: Dict[str, int] = defaultdict(int)
        self.timers: Dict[str, dict[str, float]] = defaultdict(lambda: {"count": 0, "total": 0.0})
        self.last_reset: float = time.time()

    def inc(self, key: str, amount: int = 1) -> None:
        self.counters[key] += amount

    def observe(self, key: str, value: float) -> None:
        bucket = self.timers[key]
        bucket["count"] += 1
        bucket["total"] += value

    def snapshot(self) -> dict:
        snap = {
            "counters": dict(self.counters),
            "timers": {
                name: {
                    "count": data["count"],
                    "avg": (data["total"] / data["count"]) if data["count"] else 0.0,
                }
                for name, data in self.timers.items()
            },
            "uptime": time.time() - self.last_reset,
        }
        return snap

    def format_snapshot(self) -> str:
        snap = self.snapshot()
        counter_parts = [f"{k}={v}" for k, v in sorted(snap["counters"].items())]
        timer_parts = [
            f"{name}:count={data['count']},avg_ms={data['avg']:.1f}"
            for name, data in sorted(snap["timers"].items())
        ]
        parts = []
        if counter_parts:
            parts.append("counters[" + ", ".join(counter_parts) + "]")
        if timer_parts:
            parts.append("timers[" + ", ".join(timer_parts) + "]")
        parts.append(f"uptime={snap['uptime']:.1f}s")
        return " ".join(parts)