stringPermissionToOctal function

String stringPermissionToOctal(String value, { bool withType = false, })

ex: stringPermissionToOctal('-rwxrwxrwx') => 777 value input '-rwxrwxrwx' => 777

Implementation

String stringPermissionToOctal(String value, {bool withType = false}) {
  // drwxr-xr-x
  // skip first d
  // go through remaining in sets of 3
  var output = '';
  var grouping = 0;
  int permission = 0;
  var combinedPermission = 0;
  var fileType = '';
  var charPosition = 1;
  for (var i = 0; i < value.length; i++) {
    var alpha = value[i]; //charCodeAt

    // leading '-', ie. files, not directories
    if (i == 0 && alpha == '-') {
      grouping = 0;
      if (withType) {
        fileType = 'File: ';
      }
      continue;
    }

    // If first char entered is 'd' we're dealing with a directory
    if (i == 0 && alpha == 'd') {
      grouping = 0;
      if (withType) {
        fileType = 'Directory: ';
      }
      continue;
    }

    // Valid characters entered
    if (i >= 1 && (alpha.allMatches('[rwx-]').toList().isEmpty == true)) {
      return "Invalid";
    }

    // update character position validator when user starts with read
    if (i == 0 && alpha == 'r') {
      charPosition = 0;
    }

    // char positions matter drwx-rxw-x
    if ((i == charPosition || i == (charPosition + 3) || i == (charPosition + 6)) &&
        (alpha.allMatches('[r-]').toList().isEmpty == true)) {
      return "Invalid";
    }
    if ((i == (charPosition + 1) || i == (charPosition + 4) || i == (charPosition + 7)) &&
        (alpha.allMatches('[w-]').toList().isEmpty == true)) {
      return "Invalid";
    }
    if ((i == (charPosition + 2) || i == (charPosition + 5) || i == (charPosition + 8)) &&
        (alpha.allMatches('[x-]').toList().isEmpty == true)) {
      return "Invalid";
    }

    switch (alpha) {
      case 'r':
        permission = 4;
        grouping++;
        break;
      case 'w':
        permission = 2;
        grouping++;
        break;
      case 'x':
        permission = 1;
        grouping++;
        break;
      case '-':
        permission = 0;
        grouping++;
        break;
      default:
      //permission = "Invalid";
    }

    combinedPermission += permission;

    // Process in groups of three, then reset and continue to the next batch
    if (grouping % 3 == 0) {
      output = '$output$combinedPermission';
      grouping = 0;
      combinedPermission = 0;
      permission = 0;
    }
  }
  return fileType + output;
}