<?php

namespace Kreait\Firebase\ServiceAccount\Discovery;

use Kreait\Firebase\Exception\ServiceAccountDiscoveryFailed;
use Kreait\Firebase\ServiceAccount;

class FromEnvironmentVariable
{
    /**
     * @var string
     */
    private $value;

    public function __construct(string $value)
    {
        $this->value = $value;
    }

    /**
     * @throws ServiceAccountDiscoveryFailed
     *
     * @return ServiceAccount
     */
    public function __invoke(): ServiceAccount
    {
        $msg = sprintf('%s: The environment variable "%s"', static::class, $this->value);

        if (!($path = getenv($this->value))) {
            throw new ServiceAccountDiscoveryFailed(sprintf('%s is not set.', $msg));
        }

        $msg .= sprintf(' points to "%s"', $path);

        try {
            return (new FromPath($path))();
        } catch (ServiceAccountDiscoveryFailed $e) {
            throw new ServiceAccountDiscoveryFailed(
                sprintf('%s, but has errors: %s', $msg, $e->getMessage())
            );
        }
    }
}