@bernierllc/email-template-engine/src/validation.ts

Email template processing engine with compilation, rendering, and text generation

/*
Copyright (c) 2025 Bernier LLC

This file is licensed to the client under a limited-use license.
The client may use and modify this code *only within the scope of the project it was delivered for*.
Redistribution or use in other products or commercial offerings is not permitted without written consent from Bernier LLC.
*/

/**
 * Check if template has balanced braces
 */
export function checkBalancedBraces(template: string): { balanced: boolean; position?: number } {
  let count = 0;
  for (let i = 0; i < template.length; i++) {
    if (template[i] === '{' && template[i + 1] === '{') {
      count++;
      i++; // Skip next brace
    } else if (template[i] === '}' && template[i + 1] === '}') {
      count--;
      i++; // Skip next brace
      if (count < 0) {
        return { balanced: false, position: i };
      }
    }
  }
  return { balanced: count === 0, position: count !== 0 ? template.length : undefined };
}

/**
 * Check for unclosed block helpers
 */
export function checkUnclosedBlocks(template: string): string[] {
  const unclosed: string[] = [];
  const blockStack: string[] = [];
  const blockRegex = /\{\{#(\w+).*?\}\}|\{\{\/(\w+)\}\}/g;
  let match;

  while ((match = blockRegex.exec(template)) !== null) {
    if (match[1]) {
      // Opening block
      blockStack.push(match[1]);
    } else if (match[2]) {
      // Closing block
      const last = blockStack.pop();
      if (last !== match[2]) {
        unclosed.push(match[2]);
      }
    }
  }

  // Any remaining blocks are unclosed
  return [...unclosed, ...blockStack];
}

/**
 * Check if a variable name is a built-in Handlebars helper
 */
export function isBuiltInHelper(variable: string): boolean {
  const builtIns = ['if', 'unless', 'each', 'with', 'log', 'lookup', 'else'];
  const firstWord = variable.split(/[\s.]/)[0];
  return builtIns.includes(firstWord);
}

/**
 * Infer variable type from path
 */
export function inferVariableType(path: string): 'string' | 'number' | 'boolean' | 'object' | 'array' {
  // Simple heuristic based on variable name
  if (path.includes('.length') || path.includes('.count')) return 'number';
  if (path.includes('.is') || path.includes('.has')) return 'boolean';
  if (path.includes('.items') || path.includes('.list')) return 'array';
  if (path.includes('.')) return 'object';
  return 'string';
}