refactored

lib/src/map3terms_scrambler.dart

@@ -0,0 +1,154 @@
+import 'dart:math';
+import 'map3terms_map.dart';
+
+final Map<String, String> ilist = 
+    wlist.map((key, value) => MapEntry(value, key));
+
+String f(String L, String R) {
+  int x = int.parse(L);
+  int y = int.parse(R);
+  List<String> block = [
+    "1032547698",
+    "7215839046",
+    "9532817640",
+    "1094365872",
+    "6895730412",
+    "1074389256",
+    "5749208163",
+    "8976543201",
+    "2807694315",
+    "8746293105"
+  ];
+  
+  if (x < 0 || x >= 10 || y < 0 || y >= 10) {
+    throw RangeError("Index out of bounds: x=$x, y=$y");
+  }
+  
+  return block[y][x];
+}
+
+String F(String L, String K) {
+  int x = int.parse(L);
+  int k = int.parse(K);
+  String temp = "${x * x * x * k * 3 + 23 * k * k * x * x * x + k * (x + k) + 3}";
+
+  temp = temp.padLeft(10, '0');
+
+  return temp.substring(4, 10);
+}
+
+String feistPass(String input, String k) {
+  assert(input.length == 12, "Input to feistPass must be 12 characters long");
+  
+  String L = input.substring(0, 6);
+  String R = input.substring(6, 12);
+  String Rout = "";
+  String temp = F(R, k);
+  for (int i = 0; i < 6; i++) {
+    Rout += f(L[i], temp[i]);
+  }
+  return R + Rout;
+}
+
+String key = "248473";
+
+String scrambler(String input) {
+  for (int i = 0; i < key.length; i++) {
+    input = feistPass(input, key[i]);
+  }
+  return input;
+}
+
+String unscrambler(String input) {
+  input = input.substring(6, 12) + input.substring(0, 6);
+  for (int i = 0; i < key.length; i++) {
+    input = feistPass(input, key[key.length - 1 - i]);
+  }
+  return input.substring(6, 12) + input.substring(0, 6);
+}
+
+Future<String> coordToWords(List<double> coordinate) async {
+  if (coordinate.length != 2 ||
+      coordinate[0] < -90 || coordinate[0] > 90 ||
+      coordinate[1] < -180 || coordinate[1] > 180) {
+    throw ArgumentError("Invalid coordinate values: $coordinate");
+  }
+  
+  int lat = (coordinate[0] * 10000).round() + 900000;
+  int lon = (coordinate[1] * 10000).round() + 1800000;
+
+  String latStr = lat.toString().padLeft(7, '0');
+  String lonStr = lon.toString().padLeft(7, '0');
+
+  String lat0 = latStr[0];
+  String lon0 = lonStr[0];
+
+  String latlonRest = scrambler(latStr.substring(1, 7) + lonStr.substring(1, 7));
+
+  lat = int.parse(lat0 + latlonRest.substring(0, 6).padRight(6, '0'));
+  lon = int.parse(lon0 + latlonRest.substring(6, 12).padRight(6, '0'));
+
+  String latString = lat.toString().padLeft(7, '0');
+  String lonString = lon.toString().padLeft(7, '0');
+
+  if (latString.length < 7 || lonString.length < 7) {
+    throw ArgumentError("Coordinate string lengths are incorrect: lat=$latString, lon=$lonString");
+  }
+
+  String ind1 = latString.substring(0, 5);
+  String ind2 = lonString.substring(0, 5);
+  String ind3 = "0" + latString.substring(5, 7) + lonString.substring(5, 7);
+
+  return "${wlist[ind1]}.${wlist[ind2]}.${wlist[ind3]}";
+}
+
+Future<List<double>> wordsToCoord(String words) async {
+  List<String> word = words.split(".");
+
+  // Ensure exactly 3 words are provided and each exists in the dictionary
+  if (word.length != 3 || !ilist.containsKey(word[0]) || !ilist.containsKey(word[1]) || !ilist.containsKey(word[2])) {
+    throw ArgumentError("Invalid words format: $words");
+  }
+
+  String? ind1 = ilist[word[0]];
+  String? ind2 = ilist[word[1]];
+  String? ind3 = ilist[word[2]];
+
+  if (ind1 == null || ind2 == null || ind3 == null || ind3.length < 5) {
+    throw ArgumentError("Invalid word mapping for words: $words");
+  }
+
+  String lat = ind1 + ind3.substring(1, 3);
+  String lon = ind2 + ind3.substring(3, 5);
+
+  if (lat.length < 7 || lon.length < 7) {
+    throw ArgumentError("Malformed coordinate indices: lat=$lat, lon=$lon");
+  }
+
+  String latlonRest = lat.substring(1, 7) + lon.substring(1, 7);
+  latlonRest = unscrambler(latlonRest);
+
+  lat = lat[0] + latlonRest.substring(0, 6);
+  lon = lon[0] + latlonRest.substring(6, 12);
+
+  double latitude = (int.parse(lat) - 900000) / 10000.0;
+  double longitude = (int.parse(lon) - 1800000) / 10000.0;
+
+  // Additional validation: Ensure valid latitude/longitude range
+  if (latitude < -90 || latitude > 90 || longitude < -180 || longitude > 180) {
+    throw ArgumentError("Computed coordinates out of range: lat=$latitude, lon=$longitude");
+  }
+
+  return [latitude, longitude];
+}
+
+
+void main() async {
+  List<double> coordinate = [51.50844113, -0.116708278];
+  
+  String words = await coordToWords(coordinate);
+  print("Words: $words");
+  
+  List<double> backToCoord = await wordsToCoord(words);
+  print("Coordinates: ${backToCoord[0]}, ${backToCoord[1]}");
+}