feat(validation): add validators

ts/formats/base.validator.ts

@@ -0,0 +1,64 @@
+import { ValidationLevel } from '../interfaces.js';
+import type { ValidationResult, ValidationError } from '../interfaces.js';
+
+/**
+ * Base validator class that defines common validation functionality
+ * for all invoice format validators
+ */
+export abstract class BaseValidator {
+  protected xml: string;
+  protected errors: ValidationError[] = [];
+
+  constructor(xml: string) {
+    this.xml = xml;
+  }
+
+  /**
+   * Validates XML against the specified level of validation
+   * @param level Validation level (syntax, semantic, business)
+   * @returns Result of validation
+   */
+  abstract validate(level?: ValidationLevel): ValidationResult;
+
+  /**
+   * Gets all validation errors found during validation
+   * @returns Array of validation errors
+   */
+  public getValidationErrors(): ValidationError[] {
+    return this.errors;
+  }
+
+  /**
+   * Checks if the document is valid
+   * @returns True if no validation errors were found
+   */
+  public isValid(): boolean {
+    return this.errors.length === 0;
+  }
+
+  /**
+   * Validates XML against schema
+   * @returns True if schema validation passed
+   */
+  protected abstract validateSchema(): boolean;
+
+  /**
+   * Validates business rules
+   * @returns True if business rule validation passed
+   */
+  protected abstract validateBusinessRules(): boolean;
+
+  /**
+   * Adds an error to the validation errors list
+   * @param code Error code
+   * @param message Error message
+   * @param location Location in the XML where the error occurred
+   */
+  protected addError(code: string, message: string, location: string = ''): void {
+    this.errors.push({
+      code,
+      message,
+      location
+    });
+  }
+}