validate method

String? validate(String phoneNumber)

Validates a phone number based on the provided options.

Implementation

String? validate(String phoneNumber) {
  final cleanedPhone = phoneNumber.trim();

  String? validateCountryCode(String phoneNumber) {
    for (var code in options.allowedCountryCodes ?? []) {
      if (phoneNumber.startsWith('+${code.code}')) {
        // Add '+' during validation
        return phoneNumber
            .substring(code.code.length + 1); // Remove country code
      }
    }
    return null; // No valid country code found
  }

  // Validate country code if required.
  String? phoneWithoutCountryCode = cleanedPhone;
  if (options.checkCountryCode) {
    phoneWithoutCountryCode = validateCountryCode(cleanedPhone);
    if (phoneWithoutCountryCode == null) {
      return 'Invalid country code !';
    }
  }

  // Check for minimum length.
  if (options.rules.contains(PhoneValidationRule.checkMinLength)) {
    if (phoneWithoutCountryCode.length < options.minLength) {
      return 'Phone number must be at least ${options.minLength} characters long.';
    }
  }

  // Check for maximum length.
  if (options.rules.contains(PhoneValidationRule.checkMaxLength)) {
    if (phoneWithoutCountryCode.length > options.maxLength) {
      return 'Phone number must not exceed ${options.maxLength} characters.';
    }
  }

  // Prevent special characters.
  if (options.rules.contains(PhoneValidationRule.preventSpecialCharacters) &&
      !options.allowSpecialCharacters) {
    if (RegExp(r'[^\d\+]').hasMatch(phoneWithoutCountryCode)) {
      return 'Phone number must not contain special characters.';
    }
  }

  // Check format (E.164 standard).
  if (options.rules.contains(PhoneValidationRule.checkFormat)) {
    final phoneRegex = RegExp(r'^\+?[1-9]\d{1,14}$');
    if (!phoneRegex.hasMatch(cleanedPhone)) {
      return 'Please enter a valid phone number.';
    }
  }

  return null; // All validations passed.
}