<?php

namespace App\Services;

use Carbon\CarbonImmutable;
use Illuminate\Support\Facades\Redis;

/**
 * Read-only access to device-control-service's Device Shadow in Redis.
 * Laravel never writes these keys — device-control-service owns them; this
 * is purely for the dashboard/device pages to show live state.
 */
class DeviceShadow
{
    /**
     * Full shadow snapshot for one device, one round-trip via pipeline.
     *
     * @return array{status: string, last_seen: ?CarbonImmutable, desired_state: array<string, mixed>, reported_state: array<string, mixed>}
     */
    public function snapshot(string $externalId): array
    {
        $results = Redis::pipeline(function ($pipe) use ($externalId) {
            $pipe->get("device:{$externalId}:status");
            $pipe->get("device:{$externalId}:last_seen");
            $pipe->get("device:{$externalId}:desired_state");
            $pipe->get("device:{$externalId}:reported_state");
        });

        [$status, $lastSeen, $desired, $reported] = $results;

        return [
            'status' => $status ?: 'unknown',
            'last_seen' => $lastSeen ? CarbonImmutable::createFromTimestamp((int) $lastSeen) : null,
            'desired_state' => $desired ? json_decode($desired, true) : [],
            'reported_state' => $reported ? json_decode($reported, true) : [],
        ];
    }

    /**
     * Status for many devices in a single round-trip (MGET), so the device
     * list doesn't do one Redis call per row.
     *
     * @param  array<int, string>  $externalIds
     * @return array<string, string> external_id => status ("online"/"offline"/"unknown")
     */
    public function statuses(array $externalIds): array
    {
        if (empty($externalIds)) {
            return [];
        }

        $keys = array_map(fn (string $id) => "device:{$id}:status", $externalIds);
        $values = Redis::mget($keys);

        return array_combine($externalIds, array_map(fn ($v) => $v ?: 'unknown', $values));
    }

    /**
     * external_id of every device device-control-service has ever heard
     * from over MQTT (`devices:known`, a Redis Set it maintains) — includes
     * devices that sent telemetry/ack before anyone registered them in
     * Postgres. Used to suggest an external_id when adding a device instead
     * of requiring it to be typed exactly from memory.
     *
     * @return array<int, string>
     */
    public function knownExternalIds(): array
    {
        return Redis::smembers('devices:known');
    }
}