rdlowrey/uri-dot-segment-removal.php

/**
 * https://gist.github.com/rdlowrey/5f56cc540099de9d5006.
 *
 * Remove dot segments from a URI path according to RFC3986 Section 5.2.4
 *
 * @return string
 *
 * @see http://www.ietf.org/rfc/rfc3986.txt
 */
function normalizePath(string $path)
{
    if (!str_contains($path, '.')) {
        return $path;
    }

    $inputBuffer = $path;
    $outputStack = [];

    // 2.  While the input buffer is not empty, loop as follows:
    while ('' !== $inputBuffer) {
        /*
         * A.  If the input buffer begins with a prefix of "../" or "./",
         *     then remove that prefix from the input buffer; otherwise,
         */
        if (str_starts_with($inputBuffer, './')) {
            $inputBuffer = substr($inputBuffer, 2);

            continue;
        }
        if (str_starts_with($inputBuffer, '../')) {
            $inputBuffer = substr($inputBuffer, 3);

            continue;
        }

        /*
         * B.  if the input buffer begins with a prefix of "/./" or "/.",
         *     where "." is a complete path segment, then replace that
         *     prefix with "/" in the input buffer; otherwise,
         */
        if ('/.' === $inputBuffer) {
            $outputStack[] = '/';

            break;
        }
        if (str_starts_with($inputBuffer, '/./')) {
            $inputBuffer = substr($inputBuffer, 2);

            continue;
        }

        /*
         * C.  if the input buffer begins with a prefix of "/../" or "/..",
         *     where ".." is a complete path segment, then replace that
         *     prefix with "/" in the input buffer and remove the last
         *     segment and its preceding "/" (if any) from the output
         *     buffer; otherwise,
         */
        if ('/..' === $inputBuffer) {
            array_pop($outputStack);
            $outputStack[] = '/';

            break;
        }
        if (str_starts_with($inputBuffer, '/../')) {
            array_pop($outputStack);
            $inputBuffer = substr($inputBuffer, 3);

            continue;
        }

        /*
         * D.  if the input buffer consists only of "." or "..", then remove
         *     that from the input buffer; otherwise,
         */
        if ('.' === $inputBuffer || '..' === $inputBuffer) {
            break;
        }

        /*
         * E.  move the first path segment in the input buffer to the end of
         *     the output buffer, including the initial "/" character (if
         *     any) and any subsequent characters up to, but not including,
         *     the next "/" character or the end of the input buffer.
         */
        if (($slashPos = stripos($inputBuffer, '/', 1)) === false) {
            $outputStack[] = $inputBuffer;

            break;
        }
        $outputStack[] = substr($inputBuffer, 0, $slashPos);
        $inputBuffer = substr($inputBuffer, $slashPos);
    }

    return implode('', $outputStack);
}