"""Fleet-wide metric aggregation from Agent heartbeat payloads."""

from __future__ import annotations

import json
from dataclasses import dataclass
from typing import Any


def _safe_pct(value: Any) -> float | None:
    if value is None:
        return None
    try:
        num = float(value)
    except (TypeError, ValueError):
        return None
    if num < 0 or num > 100:
        return None
    return num


def _metric_from_system_info(system_info: dict[str, Any], primary: str, fallback: str) -> float | None:
    return _safe_pct(system_info.get(primary) if system_info.get(primary) is not None else system_info.get(fallback))


@dataclass(frozen=True)
class FleetMetricAggregate:
    online_count: int
    sample_count: int
    cpu_avg: int | None
    mem_avg: int | None
    disk_avg: int | None


def aggregate_fleet_metrics(heartbeats: list[dict[str, Any]]) -> FleetMetricAggregate:
    """Aggregate Redis heartbeat hash rows (is_online + system_info JSON string)."""
    online_count = 0
    cpu_vals: list[float] = []
    mem_vals: list[float] = []
    disk_vals: list[float] = []

    for row in heartbeats:
        if row.get("is_online") in (True, "True"):
            online_count += 1
        raw = row.get("system_info") or "{}"
        try:
            info = json.loads(raw) if isinstance(raw, str) else (raw or {})
        except json.JSONDecodeError:
            info = {}
        if not isinstance(info, dict):
            continue
        cpu = _metric_from_system_info(info, "cpu_usage", "cpu")
        mem = _metric_from_system_info(info, "mem_usage", "mem")
        disk = _metric_from_system_info(info, "disk_usage", "disk")
        if cpu is not None:
            cpu_vals.append(cpu)
        if mem is not None:
            mem_vals.append(mem)
        if disk is not None:
            disk_vals.append(disk)

    sample_count = max(len(cpu_vals), len(mem_vals), len(disk_vals))

    def _avg(vals: list[float]) -> int | None:
        if not vals:
            return None
        return round(sum(vals) / len(vals))

    return FleetMetricAggregate(
        online_count=online_count,
        sample_count=sample_count,
        cpu_avg=_avg(cpu_vals),
        mem_avg=_avg(mem_vals),
        disk_avg=_avg(disk_vals),
    )