Fixed to add catch block ; and Unit tests added

Author: igajurelNCQA

Cql/CoreTests/PrimitiveTests.cs

@@ -9,6 +9,7 @@
 using Hl7.Cql.Abstractions;
 using Hl7.Cql.CodeGeneration.NET.Toolkit;
 using Hl7.Cql.Compiler;
+using Hl7.Cql.Elm;
 using Hl7.Cql.Fhir;
 using Hl7.Cql.Iso8601;
 using Hl7.Cql.Operators;
@@ -3539,5 +3540,44 @@ public void QuantityToString()
             var s = ops.ConvertQuantityToString(new CqlQuantity(125, "cm"));
             s.Should().Be("125 'cm'");
         }
+
+        [TestMethod]
+        public void Add_Date_Quantity()
+        {
+            var rc = GetNewContext();
+            var fcq = rc.Operators;
+
+            var inputDate = new CqlDate(9999, 12, 30);
+            var quantity = new CqlQuantity(1, "day");
+            CqlDate expectedDate = new CqlDate(9999, 12, 31);
+
+            var newDate = fcq.Add(inputDate, quantity);
+            Assert.IsNotNull(newDate);
+            Assert.AreEqual(expectedDate, newDate);
+
+            var inputDateMaxValue = CqlDate.MaxValue;
+
+            var newDateAddMax = fcq.Add(inputDateMaxValue, quantity);
+            Assert.IsNull(newDateAddMax);
+        }
+
+        [TestMethod]
+        public void Subtract_Date_Quantity()
+        {
+            var rc = GetNewContext();
+            var fcq = rc.Operators;
+
+            var inputDate = new CqlDate(1, 1, 2);
+            var quantity = new CqlQuantity(1, "day");
+            CqlDate expectedDate = new CqlDate(1, 1, 1);
+
+            var newDate = fcq.Subtract(inputDate, quantity);
+            Assert.IsNotNull(newDate);
+            Assert.AreEqual(expectedDate, newDate);
+
+            var inputDateMinValue = CqlDate.MinValue;
+            var newDateSubtractedMin = fcq.Subtract(inputDateMinValue, quantity);
+            Assert.IsNull(newDateSubtractedMin);
+        }
     }
 }

Cql/Cql.Abstractions/Primitives/CqlDate.cs

@@ -97,42 +97,50 @@ public static bool TryParse(string s, out CqlDate? cqlDate)
             quantity = quantity.NormalizeTo(Precision);
             var value = quantity.value!.Value;
             var dto = Value.DateTimeOffset;
-            switch (quantity.unit![0])
+            try
             {
-                case 'a':
-                    dto = dto.AddYears((int)value);
-                    break;
-                case 'm':
-                    if (quantity.unit.Length > 1)
-                    {
-                        switch (quantity.unit[1])
+                switch (quantity.unit![0])
+                {
+                    case 'a':
+                        dto = dto.AddYears((int)value);
+                        break;
+                    case 'm':
+                        if (quantity.unit.Length > 1)
                         {
-                            case 'o':
-                                dto = dto.AddMonths((int)value);
-                                break;
-                            case 'i':
-                                dto = dto.AddMinutes(Math.Truncate((double)value));
-                                break;
-                            case 's':
-                                dto = dto.AddMilliseconds(Math.Truncate((double)value));
-                                break;
-                            default: throw new ArgumentException($"Unknown date unit {quantity.unit} supplied");
+                            switch (quantity.unit[1])
+                            {
+                                case 'o':
+                                    dto = dto.AddMonths((int)value);
+                                    break;
+                                case 'i':
+                                    dto = dto.AddMinutes(Math.Truncate((double)value));
+                                    break;
+                                case 's':
+                                    dto = dto.AddMilliseconds(Math.Truncate((double)value));
+                                    break;
+                                default: throw new ArgumentException($"Unknown date unit {quantity.unit} supplied");
+                            }
                         }
-                    }
-                    break;
-                case 'd':
-                    dto = dto.AddDays((int)value!);
-                    break;
-                case 'w':
-                    dto = dto.AddDays((int)(value! * CqlDateTimeMath.DaysPerWeek));
-                    break;
-                case 'h':
-                    dto = dto.AddHours(Math.Truncate((double)value));
-                    break;
-                case 's':
-                    dto = dto.AddSeconds(Math.Truncate((double)value));
-                    break;
-                default: throw new ArgumentException($"Unknown date unit {quantity.unit} supplied");
+                        break;
+                    case 'd':
+                        dto = dto.AddDays((int)value!);
+                        break;
+                    case 'w':
+                        dto = dto.AddDays((int)(value! * CqlDateTimeMath.DaysPerWeek));
+                        break;
+                    case 'h':
+                        dto = dto.AddHours(Math.Truncate((double)value));
+                        break;
+                    case 's':
+                        dto = dto.AddSeconds(Math.Truncate((double)value));
+                        break;
+                    default: throw new ArgumentException($"Unknown date unit {quantity.unit} supplied");
+                }
+            }
+            catch (ArgumentOutOfRangeException)
+            {
+                // In cases where e.g. Predecessor is called on minimum Date.
+                return null;
             }
 
             var newIsoDate = new DateIso8601(dto, Value.Precision);