wip

packages/domain/services/PageStateValidator.ts

@@ -0,0 +1,91 @@
+import { Result } from '../../shared/result/Result';
+
+/**
+ * Configuration for page state validation.
+ * Defines expected and forbidden elements on the current page.
+ */
+export interface PageStateValidation {
+  /** Expected wizard step name (e.g., 'cars', 'track') */
+  expectedStep: string;
+  /** Selectors that MUST be present on the page */
+  requiredSelectors: string[];
+  /** Selectors that MUST NOT be present on the page */
+  forbiddenSelectors?: string[];
+}
+
+/**
+ * Result of page state validation.
+ */
+export interface PageStateValidationResult {
+  isValid: boolean;
+  message: string;
+  expectedStep: string;
+  missingSelectors?: string[];
+  unexpectedSelectors?: string[];
+}
+
+/**
+ * Domain service for validating page state during wizard navigation.
+ * 
+ * Purpose: Prevent navigation bugs by ensuring each step executes on the correct page.
+ * 
+ * Clean Architecture: This is pure domain logic with no infrastructure dependencies.
+ * It validates state based on selector presence/absence without knowing HOW to check them.
+ */
+export class PageStateValidator {
+  /**
+   * Validate that the page state matches expected conditions.
+   * 
+   * @param actualState Function that checks if selectors exist on the page
+   * @param validation Expected page state configuration
+   * @returns Result with validation outcome
+   */
+  validateState(
+    actualState: (selector: string) => boolean,
+    validation: PageStateValidation
+  ): Result<PageStateValidationResult, Error> {
+    try {
+      const { expectedStep, requiredSelectors, forbiddenSelectors = [] } = validation;
+
+      // Check required selectors are present
+      const missingSelectors = requiredSelectors.filter(selector => !actualState(selector));
+      
+      if (missingSelectors.length > 0) {
+        const result: PageStateValidationResult = {
+          isValid: false,
+          message: `Page state mismatch: Expected to be on "${expectedStep}" page but missing required elements`,
+          expectedStep,
+          missingSelectors
+        };
+        return Result.ok(result);
+      }
+
+      // Check forbidden selectors are absent
+      const unexpectedSelectors = forbiddenSelectors.filter(selector => actualState(selector));
+      
+      if (unexpectedSelectors.length > 0) {
+        const result: PageStateValidationResult = {
+          isValid: false,
+          message: `Page state mismatch: Found unexpected elements on "${expectedStep}" page`,
+          expectedStep,
+          unexpectedSelectors
+        };
+        return Result.ok(result);
+      }
+
+      // All checks passed
+      const result: PageStateValidationResult = {
+        isValid: true,
+        message: `Page state valid for "${expectedStep}"`,
+        expectedStep
+      };
+      return Result.ok(result);
+    } catch (error) {
+      return Result.err(
+        error instanceof Error 
+          ? error 
+          : new Error(`Page state validation failed: ${String(error)}`)
+      );
+    }
+  }
+}