<?php

namespace TFGraphics\SmartImport\DomainEngine;

/**
 * An ordered list of provider names for a given domain.
 * First entry = primary. Subsequent entries = fallback chain.
 *
 * Parallel mode is retained as a generic chain capability.
 * the parallel flag signals the ProviderManager to query both concurrently.
 */
final class ProviderChain
{
    /** @var string[] */
    private array $providers;
    private bool  $parallel;

    /**
     * @param string[] $providers  Ordered: [primary, fallback1, fallback2, ...]
     * @param bool     $parallel   If true, the first N providers are queried in parallel
     */
    public function __construct(array $providers, bool $parallel = false)
    {
        $this->providers = array_values(array_filter($providers, 'is_string'));
        $this->parallel  = $parallel;
    }

    /** @return string[] */
    public function getProviders(): array { return $this->providers; }

    public function getPrimary(): ?string { return $this->providers[0] ?? null; }

    /** @return string[] All except primary */
    public function getFallbacks(): array { return array_slice($this->providers, 1); }

    public function isParallel(): bool { return $this->parallel; }

    public function isEmpty(): bool { return $this->providers === []; }
}