fix empty start/end

lib/mudder_dart.dart

@@ -84,8 +84,9 @@ class SymbolTable {
       throw Exception('end param must be of type String or List<String>');
     }
 
-    start ??= num2sym[0];
-    end ??= JSShim.repeat(num2sym[num2sym.length - 1], start.length + 6);
+    start = notEmptyString(start) ?? num2sym[0];
+    end = notEmptyString(end) ??
+        JSShim.repeat(num2sym[num2sym.length - 1], start.length + 6);
     numStrings ??= 1;
     base ??= maxBase;
     numDivisions ??= numStrings + 1;

lib/src/helpers.dart

@@ -49,6 +49,22 @@ bool _isPrefixCodeLogLinear(List<String> _strings) {
 
 bool Function(List<String>) isPrefixCode = _isPrefixCodeLogLinear;
 
+bool isValidString(dynamic string) {
+  return string is List<String>
+      ? string.isNotEmpty
+      : string is String
+          ? string.trim().isNotEmpty
+          : false;
+}
+
+dynamic notEmptyString(dynamic string) {
+  return isValidString(string)
+      ? string is String
+          ? string.trim()
+          : string
+      : null;
+}
+
 List<String> iter(String char, int len) => List.generate(
       len,
       (i) => String.fromCharCode(char.codeUnitAt(0) + i),

pubspec.yaml

@@ -1,6 +1,6 @@
 name: mudder_dart
 
-version: 0.1.0
+version: 0.1.1
 
 description: >-
   Dart version of mudderjs (https://github.com/fasiha/mudderjs).

test/helpers_test.dart

@@ -5,6 +5,26 @@ void main() {
   group('helpers tests', () {
     final digits = <int>[1, 2, 3];
 
+    test('test isValidString', () {
+      expect(isValidString(null), false);
+      expect(isValidString(""), false);
+      expect(isValidString(" "), false);
+      expect(isValidString([]), false);
+      expect(isValidString("a"), true);
+      expect(isValidString(" a "), true);
+      expect(isValidString(["a"]), true);
+    });
+
+    test('test notEmptyString', () {
+      expect(notEmptyString(null), null);
+      expect(notEmptyString(""), null);
+      expect(notEmptyString(" "), null);
+      expect(notEmptyString("a"), "a");
+      expect(notEmptyString(" a "), "a");
+      expect(notEmptyString([]), null);
+      expect(notEmptyString(["a"]), ["a"]);
+    });
+
     test('test iter', () {
       final result = iter('0', 3);
       expect(result, ['0', '1', '2']);

test/mudder_test.dart

@@ -160,9 +160,9 @@ void main() {
 
   group('mudder tests', () {
     group('test mudder', () {
-      test('test invalid prev and next', () {
-        expect(() => base62.mudder(start: 1), throwsException);
+      test('test invalid start and end', () {
         expect(() => base62.mudder(start: 1), throwsException);
+        expect(() => base62.mudder(end: 1), throwsException);
       });
 
       test('test alphabet mudder simple ', () {
@@ -177,19 +177,35 @@ void main() {
         expect(result[0], "U");
       });
 
-      test('test base62 mudder prev 1', () {
+      test('test base62 mudder start v and empty end string', () {
+        expect(base62.mudder(start: "v", end: ""), ["x"]);
+      });
+
+      test('test base62 mudder start v only', () {
+        expect(base62.mudder(start: "v"), ["x"]);
+      });
+
+      test('test base62 mudder empty start and end v', () {
+        expect(base62.mudder(start: "", end: "v"), ["S"]);
+      });
+
+      test('test base62 mudder end v only', () {
+        expect(base62.mudder(end: "v"), ["S"]);
+      });
+
+      test('test base62 mudder start 1', () {
         expect(base62.mudder(start: "1"), ["V"]);
       });
 
-      test('test base62 mudder prev [1]', () {
+      test('test base62 mudder start [1]', () {
         expect(base62.mudder(start: ["1"]), ["V"]);
       });
 
-      test('test base62 mudder next 1', () {
+      test('test base62 mudder end 1', () {
         expect(base62.mudder(end: "1"), ["0V"]);
       });
 
-      test('test base62 mudder next [1]', () {
+      test('test base62 mudder end [1]', () {
         expect(base62.mudder(end: ["1"]), ["0V"]);
       });