All files / path / _common / normalize_string.ts

// Copyright 2018-2025 the Deno authors. MIT license.
// Copyright the Browserify authors. MIT License.
// Ported from https://github.com/browserify/path-browserify/
// This module is browser compatible.

import { CHAR_DOT, CHAR_FORWARD_SLASH } from "./constants.ts";

// Resolves . and .. elements in a path with directory names
export function normalizeString(
  path: string,
  allowAboveRoot: boolean,
  separator: string,
  isPathSeparator: (code: number) => boolean,
): string {
  let res = "";
  let lastSegmentLength = 0;
  let lastSlash = -1;
  let dots = 0;
  let code: number | undefined;
  for (let i = 0; i <= path.length; ++i) {
    if (i < path.length) code = path.charCodeAt(i);
    else if (isPathSeparator(code!)) break;
    else code = CHAR_FORWARD_SLASH;

    if (isPathSeparator(code!)) {
      if (lastSlash === i - 1 || dots === 1) {
        // NOOP
      } else if (lastSlash !== i - 1 && dots === 2) {
        if (
          res.length < 2 ||
          lastSegmentLength !== 2 ||
          res.charCodeAt(res.length - 1) !== CHAR_DOT ||
          res.charCodeAt(res.length - 2) !== CHAR_DOT
        ) {
          if (res.length > 2) {
            const lastSlashIndex = res.lastIndexOf(separator);
            if (lastSlashIndex === -1) {
              res = "";
              lastSegmentLength = 0;
            } else {
              res = res.slice(0, lastSlashIndex);
              lastSegmentLength = res.length - 1 - res.lastIndexOf(separator);
            }
            lastSlash = i;
            dots = 0;
            continue;
          } else if (res.length === 2 || res.length === 1) {
            res = "";
            lastSegmentLength = 0;
            lastSlash = i;
            dots = 0;
            continue;
          }
        }
        if (allowAboveRoot) {
          if (res.length > 0) res += `${separator}..`;
          else res = "..";
          lastSegmentLength = 2;
        }
      } else {
        if (res.length > 0) res += separator + path.slice(lastSlash + 1, i);
        else res = path.slice(lastSlash + 1, i);
        lastSegmentLength = i - lastSlash - 1;
      }
      lastSlash = i;
      dots = 0;
    } else if (code === CHAR_DOT && dots !== -1) {
      ++dots;
    } else {
      dots = -1;
    }
  }
  return res;
}