From 64bcb34a11020b1eeea71ad716ed1aee423770b7 Mon Sep 17 00:00:00 2001
From: Oliver Booth <me@olivr.me>
Date: Mon, 14 Feb 2022 16:24:14 +0000
Subject: [PATCH] Introduce Between clusivity

---
 X10D.Tests/src/Core/ComparableTests.cs        | 20 ++++++++++---
 X10D/src/ComparableExtensions/Clusivity.cs    | 28 +++++++++++++++++++
 .../ComparableExtensions.cs                   | 13 +++++++--
 3 files changed, 55 insertions(+), 6 deletions(-)
 create mode 100644 X10D/src/ComparableExtensions/Clusivity.cs

diff --git a/X10D.Tests/src/Core/ComparableTests.cs b/X10D.Tests/src/Core/ComparableTests.cs
index 5c7570e..72dadf6 100644
--- a/X10D.Tests/src/Core/ComparableTests.cs
+++ b/X10D.Tests/src/Core/ComparableTests.cs
@@ -9,14 +9,26 @@ namespace X10D.Tests.Core
     public class ComparableTests
     {
         /// <summary>
-        ///     Tests for <see cref="ComparableExtensions.Between{T}" />.
+        ///     Tests <see cref="ComparableExtensions.Between{T1, T2, T3}" />
         /// </summary>
         [TestMethod]
         public void Between()
         {
-            Assert.IsTrue(5.Between(2, 7));
-            Assert.IsTrue(10.Between(9, 11));
-            Assert.IsFalse(100.Between(80, 99));
+            const int lower = 5;
+            const int upper = 15;
+            const int value = 10;
+
+            Assert.IsTrue(value.Between(lower, upper), "value.Between(lower, upper)");
+            Assert.IsFalse(lower.Between(value, upper), "lower.Between(value, upper)");
+            Assert.IsFalse(upper.Between(lower, value), "upper.Between(lower, value)");
+            
+            Assert.IsTrue(upper.Between(lower, upper, Clusivity.UpperInclusive), "upper.Between(lower, upper, Clusivity.UpperInclusive)");
+            Assert.IsTrue(upper.Between(lower, upper, Clusivity.Inclusive), "upper.Between(lower, upper, Clusivity.Inclusive)");
+            Assert.IsFalse(upper.Between(lower, upper, Clusivity.LowerInclusive), "upper.Between(lower, upper, Clusivity.LowerInclusive)");
+            
+            Assert.IsTrue(lower.Between(lower, upper, Clusivity.LowerInclusive), "lower.Between(lower, upper, Clusivity.LowerInclusive)");
+            Assert.IsTrue(lower.Between(lower, upper, Clusivity.Inclusive), "lower.Between(lower, upper, Clusivity.Inclusive)");
+            Assert.IsFalse(lower.Between(lower, upper, Clusivity.UpperInclusive), "lower.Between(lower, upper, Clusivity.UpperInclusive)");
         }
     }
 }
diff --git a/X10D/src/ComparableExtensions/Clusivity.cs b/X10D/src/ComparableExtensions/Clusivity.cs
new file mode 100644
index 0000000..8ea5b8a
--- /dev/null
+++ b/X10D/src/ComparableExtensions/Clusivity.cs
@@ -0,0 +1,28 @@
+namespace X10D;
+
+/// <summary>
+///     Provides options for <see cref="ComparableExtensions.Between{T1, T2, T3}" /> clusivity.
+/// </summary>
+[Flags]
+public enum Clusivity : byte
+{
+    /// <summary>
+    ///     Indicates that the comparison will be exclusive. 
+    /// </summary>
+    Exclusive,
+    
+    /// <summary>
+    ///     Indicates that the comparison will treat the upper bound as exclusive. 
+    /// </summary>
+    UpperInclusive,
+    
+    /// <summary>
+    ///     Indicates that the comparison will treat the lower bound as exclusive. 
+    /// </summary>
+    LowerInclusive,
+    
+    /// <summary>
+    ///     Indicates that the comparison will treat both the upper and lower bound as exclusive. 
+    /// </summary>
+    Inclusive
+}
diff --git a/X10D/src/ComparableExtensions/ComparableExtensions.cs b/X10D/src/ComparableExtensions/ComparableExtensions.cs
index 3aa1650..d10052f 100644
--- a/X10D/src/ComparableExtensions/ComparableExtensions.cs
+++ b/X10D/src/ComparableExtensions/ComparableExtensions.cs
@@ -16,6 +16,7 @@ namespace X10D
         /// <param name="value">The value to compare.</param>
         /// <param name="lower">The exclusive lower bound.</param>
         /// <param name="upper">The exclusive upper bound.</param>
+        /// <param name="clusivity">The comparison clusivity.</param>
         /// <returns>
         ///     <see langword="true" /> if <paramref name="value" /> is between the <paramref name="lower" /> and
         ///     <paramref name="upper" />
@@ -43,7 +44,7 @@ namespace X10D
         /// //      True
         /// </code>
         /// </example>
-        public static bool Between<T1, T2, T3>(this T1 value, T2 lower, T3 upper)
+        public static bool Between<T1, T2, T3>(this T1 value, T2 lower, T3 upper, Clusivity clusivity = Clusivity.Exclusive)
             where T1 : IComparable<T2>, IComparable<T3>
             where T2 : IComparable<T3>
             where T3 : IComparable<T2>
@@ -60,7 +61,15 @@ namespace X10D
                     nameof(lower));
             }
 
-            return value.CompareTo(lower) > 0 && value.CompareTo(upper) < 0;
+            bool lowerComparison = (clusivity & Clusivity.LowerInclusive) != 0
+                ? value.CompareTo(lower) >= 0
+                : value.CompareTo(lower) > 0;
+
+            bool upperComparison = (clusivity & Clusivity.UpperInclusive) != 0
+                ? value.CompareTo(upper) <= 0
+                : value.CompareTo(upper) < 0;
+
+            return lowerComparison && upperComparison;
         }
 
         /// <summary>