From 65124e840368b0c1bc56e1924f384936713efd66 Mon Sep 17 00:00:00 2001
From: Jon Sagara <jon@sagarasoftware.com>
Date: Wed, 19 Jul 2023 19:14:16 -0700
Subject: [PATCH] Fixed lb to kg / kg to lb conversion error.

---
 IdParser.Test/WeightTests.cs | 30 ++++++++++++++++++++++++++++++
 IdParser/Weight.cs           | 17 ++++++++++++++---
 2 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/IdParser.Test/WeightTests.cs b/IdParser.Test/WeightTests.cs
index 8c0e85d..9ed8087 100644
--- a/IdParser.Test/WeightTests.cs
+++ b/IdParser.Test/WeightTests.cs
@@ -62,5 +62,35 @@ public void MetricDisplayTest()
 
             Assert.AreEqual("33 kg", actual);
         }
+
+        [TestMethod]
+        public void PoundsToKilogramsTest()
+        {
+            var weight = Weight.FromImperial(175);
+            var expectedKg = 79.4;
+
+            Assert.IsTrue(weight.Kilograms.Value.Equals1DigitPrecision(expectedKg));
+        }
+
+        [TestMethod]
+        public void PoundsTest()
+        {
+            // This is internally converted to kg. Ensure it is round-tripped back to the expected value.
+            var weight = Weight.FromImperial(175);
+            var expected = "175 lbs";
+
+            Assert.AreEqual(expected, weight.ToString()); ;
+        }
+    }
+
+    internal static class DoubleExtensions
+    {
+        private const double _1Digit = 0.1;
+
+        internal static bool Equals1DigitPrecision(this double value, double comparison)
+        {
+            var difference = Math.Abs(value - comparison);
+            return difference < _1Digit;
+        }
     }
 }
diff --git a/IdParser/Weight.cs b/IdParser/Weight.cs
index c55d02e..3ce4f97 100644
--- a/IdParser/Weight.cs
+++ b/IdParser/Weight.cs
@@ -11,6 +11,17 @@ public class Weight : IComparable<Weight>, IEquatable<Weight>
     {
         private const double PoundsPerKilogram = 2.20462262;
 
+        private static double PoundsToKilograms(int pounds)
+        {
+            return pounds / PoundsPerKilogram;
+        }
+
+        private static int KilogramsToPounds(double kilograms)
+        {
+            return (int)Math.Round(kilograms * PoundsPerKilogram, 0);
+        }
+
+
         // In order for JSON serialization and deserialization to work in both Json.NET
         // and ServiceStack.Text, an immutable type has to:
         // - Be a class and not a struct (immutable structs do not deserialize in ServiceStack)
@@ -34,7 +45,7 @@ public static Weight FromMetric(double kilograms)
 
         public static Weight FromImperial(int pounds)
         {
-            return new Weight(null, pounds * PoundsPerKilogram, false);
+            return new Weight(null, PoundsToKilograms(pounds), false);
         }
 
         public static Weight FromRange(WeightRange weightRange)
@@ -44,7 +55,7 @@ public static Weight FromRange(WeightRange weightRange)
 
         internal void SetImperial(int pounds)
         {
-            Kilograms = pounds * PoundsPerKilogram;
+            Kilograms = PoundsToKilograms(pounds);
             IsMetric = false;
         }
 
@@ -71,7 +82,7 @@ public override string ToString()
                 return $"{Kilograms} kg";
             }
 
-            return $"{(int)(Kilograms.Value / PoundsPerKilogram)} lbs";
+            return $"{KilogramsToPounds(Kilograms.Value)} lbs";
         }
 
         #region IComparable