<?php

namespace App\Xapi;

/**
 * The answer of /rrd_updates (XML): columns named "AVERAGE:host:<uuid>:cpu0", "AVERAGE:vm:<uuid>:memory"... and rows of values.
 * series('vm', $uuid, 'cpu0') = [[t, value], ...] oldest first.
 */
final class Rrd
{
    /** @param array<string, list<array{0: int, 1: float}>> $columns legend => points */
    public function __construct(public array $columns = [], public int $end = 0, public int $step = 5)
    {
    }

    public static function parse(string $xml): self
    {
        preg_match_all('#<entry>([^<]*)</entry>#', $xml, $legend);
        $names = $legend[1];
        $end = preg_match('#<end>(\d+)</end>#', $xml, $m) ? (int)$m[1] : 0;
        $step = preg_match('#<step>(\d+)</step>#', $xml, $m) ? (int)$m[1] : 5;
        $columns = array_fill_keys($names, []);
        preg_match_all('#<row>(.*?)</row>#s', $xml, $rows);
        foreach ($rows[1] as $row) {
            $t = preg_match('#<t>(\d+)</t>#', $row, $m) ? (int)$m[1] : 0;
            preg_match_all('#<v>([^<]*)</v>#', $row, $values);
            foreach ($values[1] as $i => $value) {
                if (isset($names[$i]) && is_numeric($value)) {
                    $columns[$names[$i]][] = [$t, (float)$value];
                }
            }
        }
        foreach ($columns as &$points) {
            usort($points, fn ($a, $b) => $a[0] <=> $b[0]);
        }
        return new self($columns, $end, $step);
    }

    /** @return list<array{0: int, 1: float}> */
    public function series(string $kind, string $uuid, string $name): array
    {
        return $this->columns["AVERAGE:$kind:$uuid:$name"] ?? [];
    }

    /** @return list<string> the data source names of one object: cpu0, memory, vif_0_rx... */
    public function names(string $kind, string $uuid): array
    {
        $out = [];
        $prefix = "AVERAGE:$kind:$uuid:";
        foreach (array_keys($this->columns) as $legend) {
            if (str_starts_with($legend, $prefix)) {
                $out[] = substr($legend, strlen($prefix));
            }
        }
        return $out;
    }

    /** The sum of several series, point by point (all CPUs, all network cards). @param list<string> $names */
    public function sum(string $kind, string $uuid, array $names, float $scale = 1.0): array
    {
        $by = [];
        foreach ($names as $name) {
            foreach ($this->series($kind, $uuid, $name) as [$t, $v]) {
                $by[$t] = ($by[$t] ?? 0) + $v * $scale;
            }
        }
        ksort($by);
        $out = [];
        foreach ($by as $t => $v) {
            $out[] = [(int)$t, $v];
        }
        return $out;
    }

    /** @param list<string> $names */
    public function average(string $kind, string $uuid, array $names, float $scale = 1.0): array
    {
        $sum = $this->sum($kind, $uuid, $names, $scale);
        $n = max(1, count($names));
        return array_map(fn ($p) => [$p[0], $p[1] / $n], $sum);
    }
}