const _DRIVE_LETTER_START_RE = /^[A-Za-z]:\//;
function normalizeWindowsPath(input = "") {
  if (!input) {
    return input;
  }
  return input.replace(/\\/g, "/").replace(_DRIVE_LETTER_START_RE, (r) => r.toUpperCase());
}

const _UNC_REGEX = /^[/\\]{2}/;
const _IS_ABSOLUTE_RE = /^[/\\](?![/\\])|^[/\\]{2}(?!\.)|^[A-Za-z]:[/\\]/;
const _DRIVE_LETTER_RE = /^[A-Za-z]:$/;
const normalize = function(path) {
  if (path.length === 0) {
    return ".";
  }
  path = normalizeWindowsPath(path);
  const isUNCPath = path.match(_UNC_REGEX);
  const isPathAbsolute = isAbsolute(path);
  const trailingSeparator = path[path.length - 1] === "/";
  path = normalizeString(path, !isPathAbsolute);
  if (path.length === 0) {
    if (isPathAbsolute) {
      return "/";
    }
    return trailingSeparator ? "./" : ".";
  }
  if (trailingSeparator) {
    path += "/";
  }
  if (_DRIVE_LETTER_RE.test(path)) {
    path += "/";
  }
  if (isUNCPath) {
    if (!isPathAbsolute) {
      return `//./${path}`;
    }
    return `//${path}`;
  }
  return isPathAbsolute && !isAbsolute(path) ? `/${path}` : path;
};
function normalizeString(path, allowAboveRoot) {
  let res = "";
  let lastSegmentLength = 0;
  let lastSlash = -1;
  let dots = 0;
  let char = null;
  for (let index = 0; index <= path.length; ++index) {
    if (index < path.length) {
      char = path[index];
    } else if (char === "/") {
      break;
    } else {
      char = "/";
    }
    if (char === "/") {
      if (lastSlash === index - 1 || dots === 1) ; else if (dots === 2) {
        if (res.length < 2 || lastSegmentLength !== 2 || res[res.length - 1] !== "." || res[res.length - 2] !== ".") {
          if (res.length > 2) {
            const lastSlashIndex = res.lastIndexOf("/");
            if (lastSlashIndex === -1) {
              res = "";
              lastSegmentLength = 0;
            } else {
              res = res.slice(0, lastSlashIndex);
              lastSegmentLength = res.length - 1 - res.lastIndexOf("/");
            }
            lastSlash = index;
            dots = 0;
            continue;
          } else if (res.length > 0) {
            res = "";
            lastSegmentLength = 0;
            lastSlash = index;
            dots = 0;
            continue;
          }
        }
        if (allowAboveRoot) {
          res += res.length > 0 ? "/.." : "..";
          lastSegmentLength = 2;
        }
      } else {
        if (res.length > 0) {
          res += `/${path.slice(lastSlash + 1, index)}`;
        } else {
          res = path.slice(lastSlash + 1, index);
        }
        lastSegmentLength = index - lastSlash - 1;
      }
      lastSlash = index;
      dots = 0;
    } else if (char === "." && dots !== -1) {
      ++dots;
    } else {
      dots = -1;
    }
  }
  return res;
}
const isAbsolute = function(p) {
  return _IS_ABSOLUTE_RE.test(p);
};

export { normalize as n };