public static function parsePatch()

in src/shipit/repo/ShipItRepo.php [138:213]
62 lines of code
15 McCabe index (conditional complexity)

  public static function parsePatch(string $patch): Iterator<string> {
    $contents = '';

    $minus_lines = 0;
    $plus_lines = 0;
    $seen_range_header = false;

    foreach (Str\split($patch, "\n") as $line) {
      $line = Regex\replace($line, re"/(\r\n|\n)/", "\n");

      if (
        Regex\matches(
          Str\trim_right($line),
          re"@^diff --git \"?[ab]/(.*?)\"? \"?[ab]/(.*?)\"?$@",
        )
      ) {
        if ($contents !== '') {
          yield $contents;
        }
        $seen_range_header = false;
        $contents = $line."\n";
        continue;
      }
      $matches = Regex\first_match(
        $line,
        re"/^@@ -\d+(,(?<minus_lines>\d+))? \+\d+(,(?<plus_lines>\d+))? @@/",
      );
      if ($matches !== null) {
        $minus_lines = $matches['minus_lines'] ?? '';
        $minus_lines = $minus_lines === '' ? 1 : (int)$minus_lines;
        $plus_lines = $matches['plus_lines'] ?? '';
        $plus_lines = $plus_lines === '' ? 1 : (int)$plus_lines;

        $contents .= $line."\n";
        $seen_range_header = true;
        continue;
      }

      if (!$seen_range_header) {
        $contents .= $line."\n";
        continue;
      }

      $leftmost = Str\slice($line, 0, 1);
      if ($leftmost === "\\") {
        $contents .= $line."\n";
        // Doesn't count as a + or - line whatever happens; if NL at EOF
        // changes, there is a + and - for the last line of content
        continue;
      }

      if ($minus_lines <= 0 && $plus_lines <= 0) {
        continue;
      }

      $leftmost = Str\slice($line, 0, 1);
      if ($leftmost === '+') {
        --$plus_lines;
      } else if ($leftmost === '-') {
        --$minus_lines;
      } else if ($leftmost === ' ') {
        // Context goes from both.
        --$plus_lines;
        --$minus_lines;
      } else {
        invariant_violation("Can't parse hunk line: %s", $line);
      }
      $contents .= $line."\n";
    }

    if ($contents !== '') {
      // If we got the patch from git-diff, there won't be the signature line
      // from format-patch
      yield $contents;
    }
  }