class DiffOnlyOutputBuilder

final class DiffOnlyOutputBuilder implements DiffOutputBuilderInterface {
    private string $header;
    public function __construct(string $header = "--- Original\n+++ New\n") {
        $this->header = $header;
    }
    public function getDiff(array $diff) : string {
        $buffer = fopen('php://memory', 'r+b');
        if ('' !== $this->header) {
            fwrite($buffer, $this->header);
            if (!str_ends_with($this->header, "\n")) {
                fwrite($buffer, "\n");
            }
        }
        foreach ($diff as $diffEntry) {
            if ($diffEntry[1] === Differ::ADDED) {
                fwrite($buffer, '+' . $diffEntry[0]);
            }
            elseif ($diffEntry[1] === Differ::REMOVED) {
                fwrite($buffer, '-' . $diffEntry[0]);
            }
            elseif ($diffEntry[1] === Differ::DIFF_LINE_END_WARNING) {
                fwrite($buffer, ' ' . $diffEntry[0]);
                continue;
                // Warnings should not be tested for line break, it will always be there
            }
            else {
                
                /* Not changed (old) 0 */
                continue;
                // we didn't write the not-changed line, so do not add a line break either
            }
            $lc = substr($diffEntry[0], -1);
            if ($lc !== "\n" && $lc !== "\r") {
                fwrite($buffer, "\n");
                // \No newline at end of file
            }
        }
        $diff = stream_get_contents($buffer, -1, 0);
        fclose($buffer);
        return $diff;
    }

}