Use "automation" instead of "workflow"

[MAILPOET-4793]

mailpoet/lib/Automation/Engine/Validation/AutomationRules/ValidStepValidationRule.php

@@ -0,0 +1,71 @@
+<?php declare(strict_types = 1);
+
+namespace MailPoet\Automation\Engine\Validation\AutomationRules;
+
+use MailPoet\Automation\Engine\Data\Automation;
+use MailPoet\Automation\Engine\Data\Step;
+use MailPoet\Automation\Engine\Data\StepValidationArgs;
+use MailPoet\Automation\Engine\Exceptions;
+use MailPoet\Automation\Engine\Integration\Payload;
+use MailPoet\Automation\Engine\Integration\Subject;
+use MailPoet\Automation\Engine\Registry;
+use MailPoet\Automation\Engine\Validation\AutomationGraph\AutomationNode;
+use MailPoet\Automation\Engine\Validation\AutomationGraph\AutomationNodeVisitor;
+
+class ValidStepValidationRule implements AutomationNodeVisitor {
+  /** @var Registry */
+  private $registry;
+
+  public function __construct(
+    Registry $registry
+  ) {
+    $this->registry = $registry;
+  }
+
+  public function initialize(Automation $automation): void {
+  }
+
+  public function visitNode(Automation $automation, AutomationNode $node): void {
+    $step = $node->getStep();
+    $registryStep = $this->registry->getStep($step->getKey());
+    if (!$registryStep) {
+      return;
+    }
+
+    $subjects = $this->collectSubjects($automation, $node->getParents());
+    $args = new StepValidationArgs($automation, $step, $subjects);
+    $registryStep->validate($args);
+  }
+
+  public function complete(Automation $automation): void {
+  }
+
+  /**
+   * @param Step[] $parents
+   * @return Subject<Payload>[]
+   */
+  private function collectSubjects(Automation $automation, array $parents): array {
+    $triggers = array_filter($parents, function (Step $step) {
+      return $step->getType() === Step::TYPE_TRIGGER;
+    });
+
+    $subjectKeys = [];
+    foreach ($triggers as $trigger) {
+      $registryTrigger = $this->registry->getTrigger($trigger->getKey());
+      if (!$registryTrigger) {
+        throw Exceptions::automationTriggerNotFound($automation->getId(), $trigger->getKey());
+      }
+      $subjectKeys = array_merge($subjectKeys, $registryTrigger->getSubjectKeys());
+    }
+
+    $subjects = [];
+    foreach (array_unique($subjectKeys) as $key) {
+      $subject = $this->registry->getSubject($key);
+      if (!$subject) {
+        throw Exceptions::subjectNotFound($key);
+      }
+      $subjects[] = $subject;
+    }
+    return $subjects;
+  }
+}