fix: add south african vat validator

[koblas]

fixes #130

[gemini-code-assist]

Hello @koblas, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

Summary of Changes

This pull request addresses issue #130 by adding a validator for South African VAT numbers. The changes include updating the README to include the new VAT entry, adding the VAT validator to the list of South African validators in src/index.ts, creating a new vat.ts file with the validation logic, and adding a corresponding test file vat.spec.ts.

Highlights

• New Validator: Adds a validator for South African VAT numbers.
• README Update: Updates the README file to include the new VAT validator.
• Integration: Integrates the new VAT validator into the existing validation framework.

Changelog

• README.md
  • Added a new row to the table describing the South African VAT validator, including its country code (ZA), type (VAT), entity (Company), and a description.
• src/index.ts
  • Added the South African VAT validator (ZA.vat) to the list of validators for the ZA country code.
• src/za/index.ts
  • Exported the new VAT validator from the src/za/index.ts file.
• src/za/vat.spec.ts
  • Created a new test file src/za/vat.spec.ts to test the VAT validator, including tests for formatting, valid VAT numbers, invalid lengths, and invalid formats.
• src/za/vat.ts
  • Created a new file src/za/vat.ts containing the VAT validator implementation, including functions for cleaning, compacting, formatting, and validating the VAT number. The VAT number must be 10 digits long, start with a 4, and contain only digits.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point in your pull request via creating an issue comment (i.e. comment on the pull request page) using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in issue comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist is currently in preview and may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments to provide feedback.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request introduces a validator for South African VAT numbers. The implementation appears correct and includes a test suite. The addition of the VAT validator to the README and index file is also well-handled. However, there are a few areas that could be improved for clarity and maintainability.

Summary of Findings

• Test case for invalid characters: The test suite includes a test case for invalid characters ('49a 9999 999'), but the assertion compares the result against InvalidFormat. It should be validated against InvalidFormat.
• Missing checksum validation: The VAT number validation logic does not include a checksum validation step. While the current implementation checks for length, format, and the starting digit, it does not verify the number's integrity using a checksum. This could lead to the acceptance of invalid VAT numbers.
• Inconsistent error message in test case: The test case 'validate:49a 9999 999' uses the same input value as 'validate:399 9999 999'. This might be a copy-paste error and should be corrected to use the correct input value for the test case.

Merge Readiness

The pull request introduces a new VAT validator for South Africa, which is a valuable addition to the library. However, the absence of checksum validation and the issues identified in the test suite should be addressed before merging. I am unable to approve this pull request, and recommend that it not be merged until the identified issues are resolved. Another reviewer should also review this code before merging.