Merge pull request #580 from hazzik/date-increment-decrement

Add methods to increment / decrement GDMDate
Serg-Norseman · Jun 27, 2024 · 97b955d · 97b955d
2 parents 894a868 + a6c0e36
commit 97b955d
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Showing 2 changed files with 150 additions and 2 deletions.
diff --git a/projects/GKCore/GDModel/GDMDate.cs b/projects/GKCore/GDModel/GDMDate.cs
@@ -135,7 +135,7 @@ public override void Clear()
         }
 
         /// <summary>
-        /// This function is intended only for checking the completeness of parts of the date 
+        /// This function is intended only for checking the completeness of parts of the date
         /// (year, month and day are defined, are not unknown).
         /// </summary>
         public bool IsValidDate()
@@ -588,5 +588,115 @@ public override void GetDateRange(out GDMDate dateStart, out GDMDate dateEnd)
             dateStart = this;
             dateEnd = this;
         }
+
+        public static GDMDate Increment(GDMDate date)
+        {
+            if (date.IsEmpty()) {
+                return Empty;
+            }
+
+            var calendar = date.fCalendar;
+            var day = date.fDay;
+            var month = date.fMonth;
+            var year = date.fYear;
+            var yearBc = date.fYearBC;
+
+            Increment(ref day, ref month, ref year, ref yearBc, calendar);
+
+            var result = new GDMDate();
+            result.SetRawData(date.fApproximated, calendar, year, yearBc, date.fYearModifier, month, day);
+            return result;
+        }
+
+        private static void Increment(ref byte day, ref byte month, ref short year, ref bool yearBC,
+            GDMCalendar calendar)
+        {
+            if (day > 0) {
+                if (day < DaysInMonth(yearBC, year, month, calendar)) {
+                    day++;
+                    return;
+                }
+
+                day = 1;
+            }
+
+            if (month > 0) {
+                if (month < 12) {
+                    month++;
+                    return;
+                }
+
+                month = 1;
+            }
+
+            if (year == 1 && yearBC) {
+                yearBC = false;
+            } else {
+                year++;
+            }
+        }
+
+        public static GDMDate Decrement(GDMDate date)
+        {
+            if (date.IsEmpty()) {
+                return Empty;
+            }
+
+            var calendar = date.fCalendar;
+            var day = date.fDay;
+            var month = date.fMonth;
+            var year = date.fYear;
+            var yearBc = date.fYearBC;
+
+            Decrement(ref yearBc, ref year, ref month, ref day, calendar);
+
+            var result = new GDMDate();
+            result.SetRawData(date.fApproximated, calendar, year, yearBc, date.fYearModifier, month, day);
+            return result;
+        }
+
+        private static void Decrement(ref bool yearBc, ref short year, ref byte month, ref byte day,
+            GDMCalendar calendar)
+        {
+            if (day > 1) {
+                day--;
+                return;
+            }
+
+            var monthDecremented = month > 1;
+            if (monthDecremented) {
+                month--;
+            } else if (month > 0) {
+                month = 12;
+            }
+
+            if (day > 0) {
+                day = DaysInMonth(yearBc, year, month, calendar);
+            }
+
+            if (monthDecremented) return;
+
+            if (year == 1 && !yearBc) {
+                yearBc = true;
+            } else {
+                year--;
+            }
+        }
+
+        private static byte DaysInMonth(bool yearBC, short year, byte month, GDMCalendar calendar)
+        {
+            if (yearBC) {
+                year -= 1;
+                if (year == 0) {
+                    year = 4; // DateTime.DaysInMonth does not support year 0
+                }
+            }
+
+            if (calendar == GDMCalendar.dcJulian && month == 2 && year % 4 == 0) {
+                return 29;
+            }
+
+            return (byte)DateTime.DaysInMonth(year, month);
+        }
     }
 }
diff --git a/projects/GKTests/GDModel/GDMDateTests.cs b/projects/GKTests/GDModel/GDMDateTests.cs
@@ -737,8 +737,46 @@ public void Test_CreateByFormattedStr()
             Assert.AreEqual("20 DEC 1980", GDMDate.CreateByFormattedStr("20/12/1980", false).StringValue);
             Assert.AreEqual("DEC 1980", GDMDate.CreateByFormattedStr("__/12/1980", false).StringValue);
             Assert.AreEqual(null, GDMDate.CreateByFormattedStr("1980", false));
-            
+
             Assert.Throws(typeof(GDMDateException), () => { GDMDate.CreateByFormattedStr("1980", true); });
         }
+
+        [Test]
+        [TestCase("", "")]
+        [TestCase("2024", "2025")]
+        [TestCase("001B.C.", "001")]
+        [TestCase("OCT 2024", "NOV 2024")]
+        [TestCase("DEC 2024", "JAN 2025")]
+        [TestCase("01 OCT 2024", "02 OCT 2024")]
+        [TestCase("31 OCT 2024", "01 NOV 2024")]
+        [TestCase("31 DEC 2024", "01 JAN 2025")]
+        [TestCase("28 FEB 1900", "01 MAR 1900")]
+        [TestCase("28 FEB 2000", "29 FEB 2000")]
+        [TestCase("29 FEB 2000", "01 MAR 2000")]
+        [TestCase("28 FEB 2023", "01 MAR 2023")]
+        [TestCase("28 FEB 2024", "29 FEB 2024")]
+        [TestCase("29 FEB 2024", "01 MAR 2024")]
+        [TestCase("28 FEB 001B.C.", "29 FEB 001B.C.")]
+        [TestCase("29 FEB 001B.C.", "01 MAR 001B.C.")]
+        [TestCase("28 FEB 005B.C.", "29 FEB 005B.C.")]
+        [TestCase("29 FEB 005B.C.", "01 MAR 005B.C.")]
+        [TestCase("28 FEB 097B.C.", "29 FEB 097B.C.")]
+        [TestCase("29 FEB 097B.C.", "01 MAR 097B.C.")]
+        [TestCase("28 FEB 101B.C.", "01 MAR 101B.C.")]
+        [TestCase("@#DJULIAN@ 29 FEB 2024", "@#DJULIAN@ 01 MAR 2024")]
+        [TestCase("@#DJULIAN@ 28 FEB 1900", "@#DJULIAN@ 29 FEB 1900")]
+        [TestCase("@#DJULIAN@ 29 FEB 1900", "@#DJULIAN@ 01 MAR 1900")]
+        [TestCase("@#DJULIAN@ 28 FEB 2000", "@#DJULIAN@ 29 FEB 2000")]
+        [TestCase("@#DJULIAN@ 29 FEB 2000", "@#DJULIAN@ 01 MAR 2000")]
+        [TestCase("@#DJULIAN@ 28 FEB 2023", "@#DJULIAN@ 01 MAR 2023")]
+        [TestCase("@#DJULIAN@ 29 FEB 2024", "@#DJULIAN@ 01 MAR 2024")]
+        public void Test_Increment_Decrement(string value, string expected)
+        {
+            var d = new GDMDate();
+            d.StringValue = value;
+            Assert.AreEqual(expected, GDMDate.Increment(d).StringValue);
+            d.StringValue = expected;
+            Assert.AreEqual(value, GDMDate.Decrement(d).StringValue);
+        }
     }
 }