d8_commerce_stock.php

<?php

// Working with commerce stock 8.x-1.x

// ****** Usfull commerce code. ******

    // Get the curent store and user 
    $currentStore = \Drupal::service('commerce_store.current_store')->getStore();
    $currentUser =   \Drupal::currentUser();
    // Load the user object
    $user = \Drupal\user\Entity\User::load($current_user->id());

    // Get a context
    $context = new Context($user, $currentStore);

// Load an order by ID
  /** @var \Drupal\commerce_order\Entity\OrderInterface $order */
  $order = \Drupal::entityTypeManager()
    ->getStorage('commerce_order')
    ->load($order_id);

// Cycle order lie items.
  foreach ($order->getItems() as $id => $order_item) {
  }

// Check if an order item is associated with (has) a Purchasable Entity.
  // Do not use if (!$order_item->hasPurchasedEntity()) {
  $purchased_entity = $order_item->getPurchasedEntity;
  if (!$purchased_entity) {
     // Get it's name
    $name = $purchased_entity->getTitle();
  }

// ******  Stock commands ******


// Get the Stock service manager
    /** @var \Drupal\commerce_stock\StockServiceManagerInterface $stockServiceManager */
    $stockServiceManager = \Drupal::service('commerce_stock.service_manager');

// Get the stock service (from the manager)
    /** @var \Drupal\commerce_stock\StockServiceInterface $stockService */
    $stock_service = $stockServiceManager->getService($entity);
    $stock_service_name = $stockServiceManager->getService($entity)->getName();

// Get the stock checker (from the service)
    $stock_checker = $stock_service->getStockChecker();

// Get the stock updater (from the service)
    $stock_updater = $stock_service->getStockUpdater();

// Get the context from a purchasable entity using the stock trait
use Drupal\commerce_stock\ContextCreatorTrait;

class X .. {
  use ContextCreatorTrait;
  .....
  $context = $this->getContext($entity);


  // Get the list of locations for a purchasable entity.
    $context = new Context($user, $currentStore);
    $locations = $stockService->getConfiguration()->getAvailabilityLocations($context, $entity);


// Get information on all active locations    
        /** @var \Drupal\commerce_stock_local\StockLocationStorage $locationStorage */
    $locationStorage = \Drupal::entityTypeManager()->getStorage('commerce_stock_location');
    $locations = $locationStorage->loadEnabled($product_variation);

    foreach ($locations as $location) {
      $id = $location->getId();
      $type = $location->getType();
      $status = $location->status->value;
      $name = $location->name->value;
      $api_id = $location->field_external_api_id->value; // a custom field
    }
    
// Common oparations

  // Check stock level    
  $stockServiceManager = \Drupal::service('commerce_stock.service_manager');
  $stock = $stockServiceManager->getStockLevel($product_variation_entity);
    

stock_updater_demo.php

<?php
namespace Drupal\stock_demo_code;

use Drupal\commerce_stock\ContextCreatorTrait;


class StockUpdateDemo {

  use ContextCreatorTrait;


  public function setStockLevel($variation, $free_stock) {
    /** @var \Drupal\commerce_stock\StockServiceManagerInterface $stockServiceManager */
    $stockServiceManager = \Drupal::service('commerce_stock.service_manager');  
    // Get the current website stock level.
    $stock_level = $stockServiceManager->getStockLevel($variation);
    // If stock level changed.
    if ($free_stock != $stock_level) {
      // Calculate the transaction stock.
      $t_stock = $free_stock - $stock_level;
      // Get the location of the transaction.
      $context = $this->getContext($variation);
      $location = $stockServiceManager->getTransactionLocation($context, $variation, $t_stock);
      // Determine the type of transaction.
      if ($t_stock > 0) {
        $transaction_type_id = StockTransactionsInterface::STOCK_IN;
      }
      else {
        $transaction_type_id = StockTransactionsInterface::STOCK_OUT;
      }
      $metadata = [
        'data' => [
          'message' => 'set by updater_demo',
        ],
      ];
      // Create the transaction
      $this->stockServiceManager->createTransaction($variation, $location->getId(), '', $t_stock, NULL, $currency_code = NULL, $transaction_type_id, $metadata);
    }
  }
}