kreiseck_validator 0.1.0

Zero-dependency validation, normalization and formatting for email, phone, URL, IBAN and credit-card input. DACH-aware. By Kreiseck.

[Kreiseck — Software Solutions]

kreiseck_validator

Validate, normalize and pretty-format the input every app collects —
email, phone, URL, IBAN and credit-card — in a few lines of Dart.
Zero dependencies. Hand-written algorithms. DACH-aware.

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kreiseck_validator is a small, zero-dependency Dart package for validating, normalizing and formatting the kinds of user input almost every app collects: email addresses, phone numbers, URLs/domains, IBANs and credit-card numbers. Every type follows the same four-operation API — isValid, validate, normalize, format — so once you learn one, you know them all.

It is built and maintained by Kreiseck Software Solutions, an Austrian software company. Every algorithm (Luhn, IBAN Mod-97, E.164 phone parsing, an offline typo-distance heuristic) is hand-written in pure Dart — no third-party dependencies, no network calls, no telemetry.

✨ Features

• 📧 Email — pragmatic syntax validation, trim + lower-case normalization, and an offline typo-domain suggestion ([e-mail] → suggests [e-mail], no DNS lookup)
• ☎️ Phone — E.164 validation and normalization, national ↔ international formatting for the DACH region (🇩🇪 DE / 🇦🇹 AT / 🇨🇭 CH), tolerant of +43 (0)… business-card notation
• 🔗 URL / Domain — scheme/host/TLD plausibility check (accepts :port, ?query, #fragment), canonical normalization, and a compact display form (https://www.example.com/ → example.com)
• 🏦 IBAN — ISO 13616 Mod-97 checksum, exact DACH length checks, pretty 4-group formatting
• 💳 Credit card — Luhn checksum, network detection (Visa / Mastercard / Amex / Discover), network-aware grouping (Amex 4-6-5, else 4-4-4-4)
• 🧱 One consistent API — isValid / validate / normalize / format (+ tryFormat) on every type
• 🪶 Zero dependencies · Apache-2.0 · null-safe · works on all Dart & Flutter platforms

📦 Install

dart pub add kreiseck_validator

import 'package:kreiseck_validator/kreiseck_validator.dart';

🚀 Quick start

📧 Email

Email.isValid('[e-mail]');           // true
Email.normalize(' [e-mail] ');       // '[e-mail]'

final result = Email.validate('[e-mail]');
switch (result) {
  case Valid(:final normalized, :final suggestions):
    print(normalized);              // '[e-mail]'
    print(suggestions.first.value); // '[e-mail]'  (offline typo hint)
  case Invalid(:final issues):
    print(issues.first.code);       // e.g. IssueCode.emailMissingAt
}

☎️ Phone

Phone.isValid('[phone]');                     // true
Phone.normalize('0660 1234567', country: Country.at); // '[phone]'
Phone.normalize('[phone]');               // '[phone]'
Phone.format('06601234567', country: Country.at);     // '[phone]'
Phone.format('[phone]', international: false);   // '0660 1234567'

National input (no +, no country code) requires the country: argument; without it, validate returns Invalid with IssueCode.phoneAmbiguousCountry. Phone.format uses a simple readable grouping (a 3-digit prefix, then the remainder), not geographic area-code-aware grouping — real DACH area codes vary in length and are out of scope here.

🔗 URL

Url.isValid('example.com');                   // true
Url.isValid('example.com:8080');              // true
Url.normalize('Example.com/path/');           // 'https://example.com/path'
Url.format('https://www.example.com/');       // 'example.com'

🏦 IBAN

Iban.isValid('AT61 1904 3002 3457 3201');     // true
Iban.normalize('at611904300234573201');       // 'AT611904300234573201'
Iban.format('AT611904300234573201');          // 'AT61 1904 3002 3457 3201'

💳 Credit card

CreditCard.isValid('4111 1111 1111 1111');    // true
CreditCard.normalize('4111-1111-1111-1111');  // '4111111111111111'
CreditCard.format('378282246310005');         // '3782 822463 10005'  (Amex 4-6-5)
CreditCard.network('4111111111111111');       // CardNetwork.visa

All format/normalize calls throw FormatException on invalid input, with one exception: Email.normalize doesn't validate at all — it's a pure trim + lower-case transform, so it never throws. Use tryFormat for a null-returning variant instead of a try/catch on the types that do throw.

🧾 The result model

validate returns a sealed ValidationResult, so a switch is exhaustive:

sealed class ValidationResult {}
class Valid   extends ValidationResult { String normalized; List<Suggestion> suggestions; }
class Invalid extends ValidationResult { List<ValidationIssue> issues; }
// ValidationIssue(IssueCode code, String message) — codes are a stable, translatable enum.

isValid(x) is shorthand for validate(x) is Valid. Error codes (IssueCode) are stable enums you can switch on and translate; the English message is only a default.

🧩 Feature matrix

Type	isValid	validate	normalize	format	tryFormat	Country scope
Email	✅	✅	✅	– (display = normalized)	–	none; offline typo suggestions only
Phone	✅	✅	✅	✅	✅	DACH (DE/AT/CH): +49/+43/+41 + national formats; other calling codes → phoneUnknownCountry
Url	✅	✅	✅	✅	✅	none (scheme/host/TLD check is global)
Iban	✅	✅	✅	✅	✅	DACH: checksum + exact length; other countries: checksum only
CreditCard	✅	✅	✅	✅	✅	none (Luhn + network detection is global)

🪶 Zero dependencies, Apache-2.0

kreiseck_validator has zero runtime dependencies — every algorithm (Luhn, Mod-97, E.164 parsing, the Damerau/OSA typo-distance heuristic) is hand-written in lib/ and documented in doc/algorithms.md. It is licensed under Apache-2.0 (see LICENSE) — free for commercial and closed-source use, with patent protection and attribution.

🌍 How behavior is pinned (cross-language)

The exact expected result of every operation, for representative inputs, is captured once as data in the language-independent JSON files under test/vectors/ (one per type). test/vectors_test.dart is a thin Dart runner that checks this package against them. A planned npm port will load the very same JSON files with its own runner, so the two implementations cannot quietly drift apart — the vectors, not either runner, are the source of truth for behavior.

🧭 About Kreiseck

[Kreiseck Software Solutions]

Kreiseck Software Solutions is an Austrian software company building practical tools for developers and businesses — from point-of-sale and payment systems to open-source developer libraries like this one. We favour lightweight, dependency-free, well-documented code that is easy to audit and easy to trust.

• 🌐 Website — kreiseck.com
• ✉️ Contact — [e-mail]
• 💙 If this package saves you time, a like on pub.dev or a ⭐ on GitHub helps others find it.

🗂️ Versioning

Semantic versioning — see the CHANGELOG.

📄 License

Apache-2.0 — see LICENSE. © 2026 Kreiseck Software Solutions.

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_{Made with care by Kreiseck Software Solutions · Austria 🇦🇹}