<?php

declare(strict_types=1);
/**
 * This file is part of Hyperf.
 *
 * @link     https://www.hyperf.io
 * @document https://hyperf.wiki
 * @contact  group@hyperf.io
 * @license  https://github.com/hyperf/hyperf/blob/master/LICENSE
 */

namespace Hyperf\LoadBalancer;

use Hyperf\LoadBalancer\Exception\NoNodesAvailableException;

class WeightedRandom extends AbstractLoadBalancer
{
    /**
     * Select an item via the load balancer.
     */
    public function select(array ...$parameters): Node
    {
        $totalWeight = 0;
        $isSameWeight = true;
        $lastWeight = null;
        $nodes = $this->nodes;
        foreach ($nodes as $node) {
            if (! $node instanceof Node) {
                continue;
            }
            $weight = $node->weight;
            $totalWeight += $weight;
            if ($lastWeight !== null && $isSameWeight && $weight !== $lastWeight) {
                $isSameWeight = false;
            }
            $lastWeight = $weight;
        }
        if ($totalWeight > 0 && ! $isSameWeight) {
            $offset = mt_rand(0, $totalWeight - 1);
            foreach ($nodes as $node) {
                $offset -= $node->weight;
                if ($offset < 0) {
                    return $node;
                }
            }
        }

        if (! $nodes) {
            throw new NoNodesAvailableException('Cannot select any node from load balancer.');
        }

        return $nodes[array_rand($nodes)];
    }
}