1. /**
  2. * Instruments JSON payloads for validation checks.
  3. * Adds a 'validate' method to objects and checks against predefined schemas.
  4. *
  5. * @param {object} obj The object to instrument.
  6. * @param {object} schema The validation schema. Keys are field names, values are validation rules.
  7. * Example: { name: 'string', age: 'number >= 0' }
  8. * @returns {object} The instrumented object.
  9. */
  10. function instrumentJsonPayload(obj, schema) {
  11. if (typeof obj !== 'object' || obj === null) {
  12. return obj; // No validation needed for non-objects
  13. }
  15. const validate = function() {
  16. for (const key in schema) {
  17. if (schema.hasOwnProperty(key)) {
  18. const value = obj[key];
  19. const rule = schema[key];
  21. if (!validateValue(value, rule)) {
  22. throw new Error(`Validation failed for field '${key}': ${rule}`);
  23. }
  24. }
  25. }
  26. };
  28. obj.validate = validate; // Add validate method to the object
  30. return obj;
  31. }
  34. /**
  35. * Validates a single value against a validation rule.
  36. * @param {*} value The value to validate.
  37. * @param {string} rule The validation rule. Example: 'string', 'number >= 0', 'array'
  38. * @returns {boolean} True if the value is valid, false otherwise.
  39. */
  40. function validateValue(value, rule) {
  41. if (rule === 'string') {
  42. return typeof value === 'string';
  43. } else if (rule === 'number >= 0') {
  44. return typeof value === 'number' && value >= 0;
  45. } else if (rule === 'number <= 100') {
  46. return typeof value === 'number' && value <= 100;
  47. } else if (rule === 'array') {
  48. return Array.isArray(value);
  49. } else if (rule.startsWith('array')) {
  50. const parts = rule.split(' ');
  51. if (parts.length === 2 && parts[0] === 'array') {
  52. return Array.isArray(value) && value.length > 0;
  53. }
  54. } else if (rule.startsWith('object')) {
  55. const parts = rule.split(' ');
  56. if (parts.length === 2 && parts[0] === 'object') {
  57. return typeof value === 'object' && value !== null && !Array.isArray(value);
  58. }
  59. }
  60. else if (rule === 'required') {
  61. return value !== undefined && value !== null;
  62. }
  63. else {
  64. // Add more rules here as needed. Default to truthiness
  65. return value;
  66. }
  67. }

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