refactor: simplify encoding mode detection logic

[vlakoff]

Refactor Encoder::chooseMode to simplify and optimize the checks for numeric and alphanumeric content.

ctype_digit() can check the entire string at once, so we can check it upfront:

if (ctype_digit($content)) {
    return Mode::NUMERIC();
}

This allows us to remove the logic related to $hasNumeric, streamlining the rest of the function.

[vlakoff]

The refactor introduced a regression: an empty string ('') was incorrectly encoded as Mode::ALPHANUMERIC() instead of Mode::BYTE().

While technically valid—since all modes can represent an empty string—Mode::BYTE() better reflects general-purpose encoding and avoids unnecessary constraints tied to the alphanumeric character set.

The most appropriate fix is to add an explicit check at the beginning:

if ('' === $content) {
    return Mode::BYTE();
}

This restores the correct behavior and clarifies the intent—helping prevent future regressions.

edit: PR has been updated with the correction.

[DASPRiD]

Very nice implementaiton, thanks! Though at the moment we still ahve failing unit tests in main, which prevents me from being able to evaluate any PRs. That needs to be fixed first.

[DASPRiD]

Please rebase against main to get the tests working.

[vlakoff]

Rebased. Please let me know what you would like to see improved (including commit messages) before considering this for merging.

[vlakoff]

A faster version of isOnlyAlphanumeric(), which takes advantage of strspn():

private static function isOnlyAlphanumeric(string $content) : bool
{
    $allowed = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:';

    return strspn($content, $allowed) === strlen($content);
}

It is much, much faster (hundreds or even thousands of times) and highly scalable, as it appears to run in close to O(1).

Edit: committed — would’ve been a shame not to use it.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.51%. Comparing base (bd2370d) to head (d6d5428).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #201      +/-   ##
============================================
- Coverage     70.58%   70.51%   -0.08%     
+ Complexity      995      993       -2     
============================================
  Files            49       49              
  Lines          3182     3174       -8     
============================================
- Hits           2246     2238       -8     
  Misses          936      936              

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[DASPRiD]

Instead of assigning this variable on every call, would it make sense to have this as a private const on the class?

[vlakoff]

Done. It looks cleaner this way.

[vlakoff]

Aside: The previous “iterate and analyze byte‑by‑byte” approach would have made sense if we were implementing a “multiple modes” algorithm (see #111). However, we are still far from that. The algorithms are already known and can be generated in PHP, but they remain complex and not straightforward to put in place.