ExampleApiClient example

api_client_example.services.yml

services:
  module_name.example.client:
    class: Drupal\api_client_example\Service\ExampleApiClient
    arguments:
      - '@http_client'

ExampleApiClient.php

<?php

namespace Drupal\api_client_example\Service;

use Drupal\Component\Serialization\Json;
use Drupal\Core\Site\Settings;
use GuzzleHttp\ClientInterface;

/**
 * Class ApiClientInterface.
 */
class ExampleApiClient {

  // Endpoints.
  const USERS_ENDPOINT = 'api/users';
  const TOKEN_ENDPOINT = 'api/token';

  // Domains.
  const PROD_DOMAIN = 'https://domain.api.com';
  const TEST_DOMAIN = 'https://domain.test.api.com';

  const API_VERSION = '1.0';

  /**
   * Client configurations.
   *
   * @var array
   */
  private array $configurations;

  /**
   * API token.
   */
  private string $token;

  /**
   * ExampleApiClient constructor.
   */
  public function __construct(private ClientInterface $httpClient) {
    // Get from settings.php, env or any other storage.
    $this->configurations = Settings::get('module_api_config', []);
  }

  /**
   * Do request.
   */
  private function doRequest(string $url, array $parameters = [], string $method = 'GET', array $success_codes = [200, 201]): array {
    $parameters = $this->processParameters($parameters, $method);
    try {
      $response = $this->httpClient->request($method, $url, $parameters);
      if (in_array($response->getStatusCode(), $success_codes)) {
        $contents = $response->getBody()->getContents();
        $json = Json::decode($contents);
        return $json['data'];
      }

    }
    catch (\Throwable $throwable) {

    }
    // Not good if we get here.
    return [];
  }

  /**
   * Get domain.
   */
  private function getApiDomain(): string {
    $domain = self::TEST_DOMAIN;
    if ($this->configurations['prod_mode']) {
      $domain = self::PROD_DOMAIN;
    }

    return sprintf('%s/%s', $domain, $this->getApiVersion());
  }

  /**
   * Get api version.
   */
  private function getApiVersion(): string {
    return self::API_VERSION;
  }

  /**
   * Process reauest parameters.
   */
  private function processParameters(array $parameters, string $method): array {
    $parameters['token'] = $this->getToken();
    return $parameters;
  }

  /**
   * Get users api data.
   */
  public function getUsers(): array {
    $url = sprintf('%s/%s', $this->getApiDomain(), self::USERS_ENDPOINT);
    return $this->doRequest($url);
  }

  /**
   * Refresh token.
   */
  private function refreshToken(): string {
    $url = sprintf('%s/%s', $this->getApiDomain(), self::TOKEN_ENDPOINT);
    $response = $this->doRequest($url);
    return $response['token'] ?? '';
  }

  /**
   * Get token.
   */
  private function getToken(): string {
    // Check if token is expired here.
    if (!$this->token) {
      $this->token = $this->refreshToken();
    }
    return $this->token;
  }

}