Fixed invalid constant for long length (#66)

 Fixes #64

Author: KeterSCP

src/Hashids.net/Hashids.cs

@@ -16,7 +16,7 @@ public partial class Hashids : IHashids
 
         private const double SEP_DIV = 3.5;
         private const double GUARD_DIV = 12.0;
-        private const int MaxNumberHashLength = 12; // Length of long.MaxValue;
+        private const int MaxNumberHashLength = 19; // Length of long.MaxValue;
 
         private readonly char[] _alphabet;
         private readonly char[] _seps;

test/Hashids.net.test/IssueSpecificTests.cs

@@ -52,5 +52,18 @@ void issue_15_it_should_return_emtpy_array_when_decoding_characters_missing_in_a
             hashids.Decode("asdfb").Length.Should().Be(0);
             hashids.DecodeLong("asdfgfdgdfgkj").Length.Should().Be(0);
         }
+
+        [Fact]
+        void issue_64_it_should_be_possible_to_encode_and_decode_long_max_value()
+        {
+            var hashids = new Hashids("salt", alphabet: "0123456789ABCDEF");
+            var hash = hashids.EncodeLong(long.MaxValue);
+
+            hash.Should().Be("58E9BDD9A7598254DA4E");
+
+            var decoded = hashids.DecodeSingleLong(hash);
+
+            decoded.Should().Be(long.MaxValue);
+        }
     }
 }