exercism-php/protein-translation/ProteinTranslation.php

<?php

/*
 * By adding type hints and enabling strict type checking, code can become
 * easier to read, self-documenting and reduce the number of potential bugs.
 * By default, type declarations are non-strict, which means they will attempt
 * to change the original type to match the type specified by the
 * type-declaration.
 *
 * In other words, if you pass a string to a function requiring a float,
 * it will attempt to convert the string value to a float.
 *
 * To enable strict mode, a single declare directive must be placed at the top
 * of the file.
 * This means that the strictness of typing is configured on a per-file basis.
 * This directive not only affects the type declarations of parameters, but also
 * a function's return type.
 *
 * For more info review the Concept on strict type checking in the PHP track
 * <link>.
 *
 * To disable strict typing, comment out the directive below.
 */

declare(strict_types=1);

class ProteinError {

  protected string $msg;

  public function __construct(string $msg) {
    $this->msg = $msg;
  }

  public function Error(): string {
    return $this->msg;
  }

}

const STOP = "STOP";
const ErrStop = new ProteinError(STOP);
const ErrInvalidCodon = new ProteinError("Invalid codon");

class ProteinTranslation {

  public function getProteins(string $rna) {
    return $this->FromRNA($rna);
  }

  private function FromRNA(string $rna): array|ProteinError {
    $names = [];
    for ($i = 0; $i < strlen($rna); $i += 3) {
      $codon = substr($rna, $i, 3);
      $nameOrError = $this->FromCodon($codon);
      if (is_string($nameOrError)) {
        $names[] = $nameOrError;
        continue;
      }
      if ($nameOrError == ErrStop) {
        return $names;
      }
      throw new InvalidArgumentException($nameOrError->Error());
    }
    return $names;
  }

  private function FromCodon(string $codon): string|ProteinError {
    $names = [
      "AUG" => "Methionine",
      "UUU" => "Phenylalanine",
      "UUC" => "Phenylalanine",
      "UUA" => "Leucine",
      "UUG" => "Leucine",
      "UCU" => "Serine",
      "UCC" => "Serine",
      "UCA" => "Serine",
      "UCG" => "Serine",
      "UAU" => "Tyrosine",
      "UAC" => "Tyrosine",
      "UGU" => "Cysteine",
      "UGC" => "Cysteine",
      "UGG" => "Tryptophan",
      "UAA" => STOP,
      "UAG" => STOP,
      "UGA" => STOP,
    ];
    @$name = $names[$codon];
    if (empty($name)) {
      return ErrInvalidCodon;
    }
    if ($name == STOP) {
      return ErrStop;
    }
    return $name;
  }

}