Convert WorkflowStepValidator to node-visitor-based rules

[MAILPOET-4659]

mailpoet/lib/Automation/Engine/Validation/WorkflowRules/UnknownStepRule.php

@@ -0,0 +1,64 @@
+<?php declare(strict_types = 1);
+
+namespace MailPoet\Automation\Engine\Validation\WorkflowRules;
+
+use MailPoet\Automation\Engine\Data\Workflow;
+use MailPoet\Automation\Engine\Exceptions;
+use MailPoet\Automation\Engine\Exceptions\InvalidStateException;
+use MailPoet\Automation\Engine\Registry;
+use MailPoet\Automation\Engine\Storage\WorkflowStorage;
+use MailPoet\Automation\Engine\Validation\WorkflowGraph\WorkflowNode;
+use MailPoet\Automation\Engine\Validation\WorkflowGraph\WorkflowNodeVisitor;
+
+class UnknownStepRule implements WorkflowNodeVisitor {
+  /** @var Registry */
+  private $registry;
+
+  /** @var WorkflowStorage */
+  private $workflowStorage;
+
+  /** @var Workflow|null|false */
+  private $cachedExistingWorkflow = false;
+
+  public function __construct(
+    Registry $registry,
+    WorkflowStorage $workflowStorage
+  ) {
+    $this->registry = $registry;
+    $this->workflowStorage = $workflowStorage;
+  }
+
+  public function initialize(Workflow $workflow): void {
+    $this->cachedExistingWorkflow = false;
+  }
+
+  public function visitNode(Workflow $workflow, WorkflowNode $node): void {
+    $step = $node->getStep();
+    $registryStep = $this->registry->getStep($step->getKey());
+
+    // step not registered (e.g. plugin was deactivated) - allow saving it only if it hasn't changed
+    if (!$registryStep) {
+      $currentWorkflow = $this->getCurrentWorkflow($workflow);
+      $currentStep = $currentWorkflow ? ($currentWorkflow->getSteps()[$step->getId()] ?? null) : null;
+      if (!$currentStep || $step->toArray() !== $currentStep->toArray()) {
+        throw Exceptions::workflowStepModifiedWhenUnknown($step);
+      }
+    }
+  }
+
+  public function complete(Workflow $workflow): void {
+  }
+
+  private function getCurrentWorkflow(Workflow $workflow): ?Workflow {
+    try {
+      $id = $workflow->getId();
+      if ($this->cachedExistingWorkflow === false) {
+        $this->cachedExistingWorkflow = $this->workflowStorage->getWorkflow($id);
+      }
+    } catch (InvalidStateException $e) {
+      // for new workflows, no workflow ID is set
+      $this->cachedExistingWorkflow = null;
+    }
+    return $this->cachedExistingWorkflow;
+  }
+}