<?php

namespace App\Services;

use App\Models\MetricSample;
use App\Models\Server;

/**
 * Turns persisted per-minute metric samples into a bucketed cpu/mem/disk (% average) + load series
 * for the Server-Details history chart. Each bucket is the AVERAGE of the samples that fall in it
 * (gauges, not counters); a bucket with no samples is null so the chart shows a gap instead of
 * fabricating a value. Mirrors the WireGuard traffic-series shape.
 */
class MetricHistory
{
    /**
     * @return array{window:int, points:array<int,array{t:int,cpu:?int,mem:?int,disk:?int,load:?float}>}
     */
    public function series(Server $server, int $windowSeconds, int $buckets = 80): array
    {
        $windowSeconds = max(60, $windowSeconds);
        $buckets = max(1, $buckets);
        $now = time();
        $from = $now - $windowSeconds;
        $width = $windowSeconds / $buckets;

        $sum = array_fill(0, $buckets, ['cpu' => 0, 'mem' => 0, 'disk' => 0, 'load' => 0.0, 'n' => 0]);

        $rows = MetricSample::query()
            ->where('server_id', $server->id)
            ->where('sampled_at', '>=', now()->subSeconds($windowSeconds))
            ->orderBy('sampled_at')
            ->get(['cpu', 'mem', 'disk', 'load', 'sampled_at']);

        foreach ($rows as $r) {
            $idx = (int) floor(($r->sampled_at->getTimestamp() - $from) / $width);
            if ($idx < 0) {
                continue;
            }
            if ($idx >= $buckets) {
                $idx = $buckets - 1; // a sample exactly on the right edge belongs to the last bucket
            }
            $sum[$idx]['cpu'] += (int) $r->cpu;
            $sum[$idx]['mem'] += (int) $r->mem;
            $sum[$idx]['disk'] += (int) $r->disk;
            $sum[$idx]['load'] += (float) $r->load;
            $sum[$idx]['n']++;
        }

        $points = [];
        for ($i = 0; $i < $buckets; $i++) {
            $n = $sum[$i]['n'];
            $points[] = [
                't' => (int) round($from + ($i + 0.5) * $width),
                'cpu' => $n ? (int) round($sum[$i]['cpu'] / $n) : null,
                'mem' => $n ? (int) round($sum[$i]['mem'] / $n) : null,
                'disk' => $n ? (int) round($sum[$i]['disk'] / $n) : null,
                'load' => $n ? round($sum[$i]['load'] / $n, 2) : null,
            ];
        }

        return ['window' => $windowSeconds, 'points' => $points];
    }
}