// a port of Go's filepath.Walk

import { promises as fs } from "fs";
import path from "path";

var Walk = {};
var _withFileTypes = { withFileTypes: true };
var _skipDir = new Error("skip this directory");
var _noopts = {};

function pass(err) {
  return err;
}

function skipOrThrow(err) {
  if (!(err instanceof Error)) {
    // go
    return false;
  }
  if (_skipDir === err) {
    // skip
    return true;
  }
  // throw
  throw err;
}

Walk.skipDir = _skipDir;

Walk.walk = async function _walk(root, walker, opts) {
  if (!opts) {
    opts = _noopts;
  }

  // Special case of the very first item, root
  var err;
  var stat = await fs.lstat(root).catch(function (e) {
    err = e;
    return null;
  });
  if (stat) {
    stat.name = path.basename(path.resolve(root));
  }

  /* similar to function in main walk loop */
  var uerr = await walker(err, root, stat).then(pass).catch(pass);
  if (skipOrThrow(uerr) || err) {
    return;
  }

  if (false === opts.withFileTypes) {
    stat = stat.name;
  }
  if (opts.sort) {
    stat = (opts.sort([stat]) || [])[0];
  }

  if (stat && stat.isDirectory()) {
    return _walkHelper(root, stat, walker, opts);
  }
  /* end */
};

async function _walkHelper(root, prevEnt, walker, opts) {
  var err;
  var _readdirOpts;
  if (false !== opts.withFileTypes) {
    _readdirOpts = _withFileTypes;
  }
  var dirents = await fs.readdir(root, _readdirOpts).catch(function (e) {
    err = e;
  });
  if (err) {
    return walker(err, root, prevEnt);
  }
  if (opts.sort) {
    dirents = opts.sort(dirents);
  }

  var dirent;
  var pathname;
  for (dirent of dirents) {
    if ("string" === typeof dirent) {
      pathname = path.join(root, dirent);
      dirent = await fs.lstat(path.join(root)).catch(function (e) {
        err = e;
      });
    } else {
      pathname = path.join(root, dirent.name);
    }

    /* main inner loop */
    err = await walker(err, pathname, dirent).then(pass).catch(pass);
    if (skipOrThrow(err)) {
      continue;
    }

    // "walk does not follow symbolic links"
    if (dirent.isDirectory()) {
      await _walkHelper(path.join(root, dirent.name), dirent, walker, opts);
    }
    /* end */
  }
}

export default Walk;