class AbstractChunkOutputBuilder

abstract class AbstractChunkOutputBuilder implements DiffOutputBuilderInterface {
    
    /**
     * Takes input of the diff array and returns the common parts.
     * Iterates through diff line by line.
     */
    protected function getCommonChunks(array $diff, int $lineThreshold = 5) : array {
        $diffSize = count($diff);
        $capturing = false;
        $chunkStart = 0;
        $chunkSize = 0;
        $commonChunks = [];
        for ($i = 0; $i < $diffSize; $i++) {
            if ($diff[$i][1] === 0) {
                if ($capturing === false) {
                    $capturing = true;
                    $chunkStart = $i;
                    $chunkSize = 0;
                }
                else {
                    $chunkSize++;
                }
            }
            elseif ($capturing !== false) {
                if ($chunkSize >= $lineThreshold) {
                    $commonChunks[$chunkStart] = $chunkStart + $chunkSize;
                }
                $capturing = false;
            }
        }
        if ($capturing !== false && $chunkSize >= $lineThreshold) {
            $commonChunks[$chunkStart] = $chunkStart + $chunkSize;
        }
        return $commonChunks;
    }

}