Added negative TimeSpan handling (#1666)

- Added unit tests for the TimeSpanTypeReader
- Fixes https://github.com/discord-net/Discord.Net/issues/1657

src/Discord.Net.Commands/Readers/TimeSpanTypeReader.cs

@@ -6,30 +6,50 @@ namespace Discord.Commands
 {
     internal class TimeSpanTypeReader : TypeReader
     {
-        private static readonly string[] Formats = {
-            "%d'd'%h'h'%m'm'%s's'", //4d3h2m1s
-            "%d'd'%h'h'%m'm'",      //4d3h2m
-            "%d'd'%h'h'%s's'",      //4d3h  1s
-            "%d'd'%h'h'",           //4d3h
-            "%d'd'%m'm'%s's'",      //4d  2m1s
-            "%d'd'%m'm'",           //4d  2m
-            "%d'd'%s's'",           //4d    1s
-            "%d'd'",                //4d
-            "%h'h'%m'm'%s's'",      //  3h2m1s
-            "%h'h'%m'm'",           //  3h2m
-            "%h'h'%s's'",           //  3h  1s
-            "%h'h'",                //  3h
-            "%m'm'%s's'",           //    2m1s
-            "%m'm'",                //    2m
-            "%s's'",                //      1s
+        /// <summary>
+        /// TimeSpan try parse formats.
+        /// </summary>
+        private static readonly string[] Formats =
+        {
+            "%d'd'%h'h'%m'm'%s's'", // 4d3h2m1s
+            "%d'd'%h'h'%m'm'",      // 4d3h2m
+            "%d'd'%h'h'%s's'",      // 4d3h  1s
+            "%d'd'%h'h'",           // 4d3h
+            "%d'd'%m'm'%s's'",      // 4d  2m1s
+            "%d'd'%m'm'",           // 4d  2m
+            "%d'd'%s's'",           // 4d    1s
+            "%d'd'",                // 4d
+            "%h'h'%m'm'%s's'",      //   3h2m1s
+            "%h'h'%m'm'",           //   3h2m
+            "%h'h'%s's'",           //   3h  1s
+            "%h'h'",                //   3h
+            "%m'm'%s's'",           //     2m1s
+            "%m'm'",                //     2m
+            "%s's'",                //       1s
         };
 
         /// <inheritdoc />
         public override Task<TypeReaderResult> ReadAsync(ICommandContext context, string input, IServiceProvider services)
         {
-            return (TimeSpan.TryParseExact(input.ToLowerInvariant(), Formats, CultureInfo.InvariantCulture, out var timeSpan))
-                ? Task.FromResult(TypeReaderResult.FromSuccess(timeSpan))
-                : Task.FromResult(TypeReaderResult.FromError(CommandError.ParseFailed, "Failed to parse TimeSpan"));
+            if (string.IsNullOrEmpty(input))
+                throw new ArgumentException(message: $"{nameof(input)} must not be null or empty.", paramName: nameof(input));
+
+            var isNegative = input[0] == '-'; // Char for CultureInfo.InvariantCulture.NumberFormat.NegativeSign
+            if (isNegative)
+            {
+                input = input.Substring(1);
+            }
+
+            if (TimeSpan.TryParseExact(input.ToLowerInvariant(), Formats, CultureInfo.InvariantCulture, out var timeSpan))
+            {
+                return isNegative
+                    ? Task.FromResult(TypeReaderResult.FromSuccess(-timeSpan))
+                    : Task.FromResult(TypeReaderResult.FromSuccess(timeSpan));
+            }
+            else
+            {
+                return Task.FromResult(TypeReaderResult.FromError(CommandError.ParseFailed, "Failed to parse TimeSpan"));
+            }
         }
     }
 }

test/Discord.Net.Tests.Unit/TimeSpanTypeReaderTests.cs

@@ -0,0 +1,70 @@
+using Discord.Commands;
+using System;
+using Xunit;
+
+namespace Discord
+{
+    public class TimeSpanTypeReaderTests
+    {
+        [Theory]
+        [InlineData("4d3h2m1s", false)]    // tests format "%d'd'%h'h'%m'm'%s's'"
+        [InlineData("4d3h2m", false)]      // tests format "%d'd'%h'h'%m'm'"
+        [InlineData("4d3h1s", false)]      // tests format "%d'd'%h'h'%s's'"
+        [InlineData("4d3h", false)]        // tests format "%d'd'%h'h'"
+        [InlineData("4d2m1s", false)]      // tests format "%d'd'%m'm'%s's'"
+        [InlineData("4d2m", false)]        // tests format "%d'd'%m'm'"
+        [InlineData("4d1s", false)]        // tests format "%d'd'%s's'"
+        [InlineData("4d", false)]          // tests format "%d'd'"
+        [InlineData("3h2m1s", false)]      // tests format "%h'h'%m'm'%s's'"
+        [InlineData("3h2m", false)]        // tests format "%h'h'%m'm'"
+        [InlineData("3h1s", false)]        // tests format "%h'h'%s's'"
+        [InlineData("3h", false)]          // tests format "%h'h'"
+        [InlineData("2m1s", false)]        // tests format "%m'm'%s's'"
+        [InlineData("2m", false)]          // tests format "%m'm'"
+        [InlineData("1s", false)]          // tests format "%s's'"
+        // Negatives
+        [InlineData("-4d3h2m1s", true)]    // tests format "-%d'd'%h'h'%m'm'%s's'"
+        [InlineData("-4d3h2m", true)]      // tests format "-%d'd'%h'h'%m'm'"
+        [InlineData("-4d3h1s", true)]      // tests format "-%d'd'%h'h'%s's'"
+        [InlineData("-4d3h", true)]        // tests format "-%d'd'%h'h'"
+        [InlineData("-4d2m1s", true)]      // tests format "-%d'd'%m'm'%s's'"
+        [InlineData("-4d2m", true)]        // tests format "-%d'd'%m'm'"
+        [InlineData("-4d1s", true)]        // tests format "-%d'd'%s's'"
+        [InlineData("-4d", true)]          // tests format "-%d'd'"
+        [InlineData("-3h2m1s", true)]      // tests format "-%h'h'%m'm'%s's'"
+        [InlineData("-3h2m", true)]        // tests format "-%h'h'%m'm'"
+        [InlineData("-3h1s", true)]        // tests format "-%h'h'%s's'"
+        [InlineData("-3h", true)]          // tests format "-%h'h'"
+        [InlineData("-2m1s", true)]        // tests format "-%m'm'%s's'"
+        [InlineData("-2m", true)]          // tests format "-%m'm'"
+        [InlineData("-1s", true)]          // tests format "-%s's'"
+        public void TestTimeSpanParse(string input, bool isNegative)
+        {
+            var reader = new TimeSpanTypeReader();
+            var result = reader.ReadAsync(null, input, null).Result;
+            Assert.True(result.IsSuccess);
+
+            var actual = (TimeSpan)result.BestMatch;
+            Assert.True(actual != TimeSpan.Zero);
+
+            if (isNegative)
+            {
+                Assert.True(actual < TimeSpan.Zero);
+
+                Assert.True(actual.Seconds == 0 || actual.Seconds == -1);
+                Assert.True(actual.Minutes == 0 || actual.Minutes == -2);
+                Assert.True(actual.Hours == 0 || actual.Hours == -3);
+                Assert.True(actual.Days == 0 || actual.Days == -4);
+            }
+            else
+            {
+                Assert.True(actual > TimeSpan.Zero);
+
+                Assert.True(actual.Seconds == 0 || actual.Seconds == 1);
+                Assert.True(actual.Minutes == 0 || actual.Minutes == 2);
+                Assert.True(actual.Hours == 0 || actual.Hours == 3);
+                Assert.True(actual.Days == 0 || actual.Days == 4);
+            }
+        }
+    }
+}