<?php

declare(strict_types=1);

namespace Belevo\EnelixEMS;

use InvalidArgumentException;

/** Read-only active-import counter sum, independent of the legacy energy counter.
 * Observation timestamps are NOT proof of a billing-quarter boundary or history.
 */
final class NetzfahrplanV4Bezugszaehler
{
    public static function quellen(array $sources): array
    {
        if ($sources === [] || count($sources) > 8
            || array_keys($sources) !== range(0, count($sources) - 1)) {
            throw new InvalidArgumentException('V4 benoetigt 1 bis 8 explizite Wirkenergie-Bezugsquellen.');
        }
        $result = [];
        $parent = null;
        foreach ($sources as $source) {
            if (!is_array($source) || count($source) !== 5
                || ($source['Messgroesse'] ?? null) !== 'WirkenergieBezug') {
                throw new InvalidArgumentException('V4 Bezugszaehler: Messgroesse oder Quellenschema ungueltig.');
            }
            $id = $source['VariableID'] ?? null;
            $pid = $source['ElternID'] ?? null;
            $ident = $source['Ident'] ?? null;
            $factor = $source['FaktorZuKWh'] ?? null;
            if (!is_int($id) || $id <= 0 || !is_int($pid) || $pid <= 0
                || !is_string($ident) || !preg_match('/^[A-Za-z][A-Za-z0-9_]{0,63}$/D', $ident)
                || (!is_int($factor) && !is_float($factor)) || !is_finite((float) $factor)
                || $factor <= 0 || $factor > 1.0e6 || isset($result[$id])) {
                throw new InvalidArgumentException('V4 Bezugszaehler: ID, Ident, Einheit oder doppelte Quelle ungueltig.');
            }
            if ($parent !== null && $parent !== $pid) {
                throw new InvalidArgumentException('V4 T1/T2 muessen zum selben physischen Bezugszaehler gehoeren.');
            }
            $parent = $pid;
            foreach ($result as $existing) {
                if ($existing['Ident'] === $ident) {
                    throw new InvalidArgumentException('V4 Bezugszaehler: Register doppelt angegeben.');
                }
            }
            $result[$id] = ['VariableID' => $id, 'ElternID' => $pid, 'Ident' => $ident,
                'FaktorZuKWh' => (float) $factor, 'Messgroesse' => 'WirkenergieBezug'];
        }
        ksort($result, SORT_NUMERIC);
        return array_values($result);
    }

    public static function identitaet(array $sources): string
    {
        // Source/factor changes invalidate old measurement evidence; names do not matter.
        return 'symcon-active-import:' . hash('sha256', json_encode(self::quellen($sources),
            JSON_THROW_ON_ERROR | JSON_PRESERVE_ZERO_FRACTION));
    }

    private static function probe(array $source, callable $read, int $now, int $maxAge): array
    {
        $m = $read($source['VariableID']);
        if (!is_array($m) || ($m['parentID'] ?? null) !== $source['ElternID']
            || ($m['ident'] ?? null) !== $source['Ident']) {
            throw new InvalidArgumentException('V4 Bezugszaehler: Variable passt nicht zum konfigurierten Register.');
        }
        $value = $m['value'] ?? null;
        $updated = $m['updated'] ?? null;
        if ((!is_int($value) && !is_float($value)) || !is_finite((float) $value) || $value < 0
            || !is_int($updated) || $updated <= 0 || $updated > $now || $now - $updated > $maxAge) {
            throw new InvalidArgumentException('V4 Bezugszaehler: Teilwert fehlt, ist veraltet oder ungueltig.');
        }
        $kwh = (float) $value * $source['FaktorZuKWh'];
        if (!is_finite($kwh) || $kwh > 1.0e12) {
            throw new InvalidArgumentException('V4 Bezugszaehler: Energie ausserhalb des Messbereichs.');
        }
        return ['variableId' => $source['VariableID'], 'rawValue' => (float) $value,
            'totalKwh' => $kwh, 'updatedAt' => $updated];
    }

    /** $read must return only value, updated, ident, parentID. Never uses an archive fallback. */
    public static function lesen(array $sources, callable $read, int $now, int $maxAge = 60, int $maxSkew = 2): array
    {
        if ($now <= 0 || $maxAge < 1 || $maxAge > 300 || $maxSkew < 0 || $maxSkew > 5) {
            throw new InvalidArgumentException('V4 Bezugszaehler: Zeitfenster ungueltig.');
        }
        $sources = self::quellen($sources);
        $samples = [];
        foreach ($sources as $source) {
            $samples[] = self::probe($source, $read, $now, $maxAge);
        }
        // Reread all channels to reject concurrent updates, including changes in the same second.
        foreach ($sources as $i => $source) {
            if ($samples[$i] !== self::probe($source, $read, $now, $maxAge)) {
                throw new InvalidArgumentException('V4 Bezugszaehler wurde waehrend des Lesens aktualisiert.');
            }
        }
        $times = array_column($samples, 'updatedAt');
        if (max($times) - min($times) > $maxSkew) {
            throw new InvalidArgumentException('V4 Bezugszaehler: T1/T2-Zeitpunkte liegen zu weit auseinander.');
        }
        return ['meterId' => self::identitaet($sources), 'quantity' => 'active_import', 'unit' => 'kWh',
            'totalKwh' => array_sum(array_column($samples, 'totalKwh')),
            'observedAt' => gmdate('c', $now), 'sourceObservationFrom' => gmdate('c', min($times)),
            'sourceObservationUntil' => gmdate('c', max($times)), 'components' => $samples,
            'billingEvidence' => false, 'historyComplete' => false];
    }
}