simplify date operators by making SDate.GetHashCode() return unique ordered values, expand unit tests (#307)

1 files changed, 56 insertions, 124 deletions

diff --git a/src/StardewModdingAPI/Utilities/SDate.cs b/src/StardewModdingAPI/Utilities/SDate.cs
index fdeffe80..5f7ff030 100644
--- a/src/StardewModdingAPI/Utilities/SDate.cs
+++ b/src/StardewModdingAPI/Utilities/SDate.cs
@@ -13,6 +13,9 @@ namespace StardewModdingAPI.Utilities
         /// <summary>The internal season names in order.</summary>
         private readonly string[] Seasons = { "spring", "summer", "fall", "winter" };
 
+        /// <summary>The number of seasons in a year.</summary>
+        private int SeasonsInYear => this.Seasons.Length;
+
         /// <summary>The number of days in a season.</summary>
         private readonly int DaysInSeason = 28;
 
@@ -77,10 +80,8 @@ namespace StardewModdingAPI.Utilities
             // handle season transition
             if (day > this.DaysInSeason || day < 1)
             {
-                // get current season index
-                int curSeasonIndex = Array.IndexOf(this.Seasons, this.Season);
-                if (curSeasonIndex == -1)
-                    throw new InvalidOperationException($"The current season '{this.Season}' wasn't recognised.");
+                // get season index
+                int curSeasonIndex = this.GetSeasonIndex();
 
                 // get season offset
                 int seasonOffset = day / this.DaysInSeason;
@@ -94,7 +95,7 @@ namespace StardewModdingAPI.Utilities
             }
 
             // validate
-            if(year < 1)
+            if (year < 1)
                 throw new ArithmeticException($"Adding {offset} days to {this} would result in invalid date {day:00} {season} {year}.");
 
             // return new date
@@ -116,157 +117,88 @@ namespace StardewModdingAPI.Utilities
         /*********
         ** Operator methods
         *********/
-
-        /// <summary>
-        /// Equality operator. Tests the date being equal to each other
-        /// </summary>
-        /// <param name="s1">The first date being compared</param>
-        /// <param name="s2">The second date being compared</param>
+        /// <summary>Get whether one date is equal to another.</summary>
+        /// <param name="date">The base date to compare.</param>
+        /// <param name="other">The other date to compare.</param>
         /// <returns>The equality of the dates</returns>
-        public static bool operator ==(SDate s1, SDate s2)
+        public static bool operator ==(SDate date, SDate other)
         {
-            if (s1.Day == s2.Day && s1.Year == s2.Year && s1.Season == s2.Season)
-                return true;
-            else
-                return false;
+            return date?.GetHashCode() == other?.GetHashCode();
         }
 
-        /// <summary>
-        /// Inequality operator. Tests the date being not equal to each other
-        /// </summary>
-        /// <param name="s1">The first date being compared</param>
-        /// <param name="s2">The second date being compared</param>
-        /// <returns>The inequality of the dates</returns>
-        public static bool operator !=(SDate s1, SDate s2)
+        /// <summary>Get whether one date is not equal to another.</summary>
+        /// <param name="date">The base date to compare.</param>
+        /// <param name="other">The other date to compare.</param>
+        public static bool operator !=(SDate date, SDate other)
         {
-            if (s1.Day == s2.Day && s1.Year == s2.Year && s1.Season == s2.Season)
-                return false;
-            else
-                return true;
+            return date?.GetHashCode() != other?.GetHashCode();
         }
 
-        /// <summary>
-        /// Less than operator. Tests the date being less than to each other
-        /// </summary>
-        /// <param name="s1">The first date being compared</param>
-        /// <param name="s2">The second date being compared</param>
-        /// <returns>If the dates are less than</returns>
-        public static bool operator >(SDate s1, SDate s2)
+        /// <summary>Get whether one date is more than another.</summary>
+        /// <param name="date">The base date to compare.</param>
+        /// <param name="other">The other date to compare.</param>
+        public static bool operator >(SDate date, SDate other)
         {
-            if (s1.Year > s2.Year)
-                return true;
-            else if (s1.Year == s2.Year)
-            {
-                if (s1.Season == "winter" && s2.Season != "winter")
-                    return true;
-                else if (s1.Season == s2.Season && s1.Day > s2.Day)
-                    return true;
-                if (s1.Season == "fall" && (s2.Season == "summer" || s2.Season == "spring"))
-                    return true;
-                if (s1.Season == "summer" && s2.Season == "spring")
-                    return true;
-            }
-
-            return false;
+            return date?.GetHashCode() > other?.GetHashCode();
         }
 
-        /// <summary>
-        /// Less or equal than operator. Tests the date being less than or equal to each other
-        /// </summary>
-        /// <param name="s1">The first date being compared</param>
-        /// <param name="s2">The second date being compared</param>
-        /// <returns>If the dates are less than or equal than</returns>
-        public static bool operator >=(SDate s1, SDate s2)
+        /// <summary>Get whether one date is more than or equal to another.</summary>
+        /// <param name="date">The base date to compare.</param>
+        /// <param name="other">The other date to compare.</param>
+        public static bool operator >=(SDate date, SDate other)
         {
-            if (s1.Year > s2.Year)
-                return true;
-            else if (s1.Year == s2.Year)
-            {
-                if (s1.Season == "winter" && s2.Season != "winter")
-                    return true;
-                else if (s1.Season == s2.Season && s1.Day >= s2.Day)
-                    return true;
-                if (s1.Season == "fall" && (s2.Season == "summer" || s2.Season == "spring"))
-                    return true;
-                if (s1.Season == "summer" && s2.Season == "spring")
-                    return true;
-            }
-
-            return false;
+            return date?.GetHashCode() >= other?.GetHashCode();
         }
 
-        /// <summary>
-        /// Greater or equal than operator. Tests the date being greater than or equal to each other
-        /// </summary>
-        /// <param name="s1">The first date being compared</param>
-        /// <param name="s2">The second date being compared</param>
-        /// <returns>If the dates are greater than or equal than</returns>
-        public static bool operator <=(SDate s1, SDate s2)
+        /// <summary>Get whether one date is less than or equal to another.</summary>
+        /// <param name="date">The base date to compare.</param>
+        /// <param name="other">The other date to compare.</param>
+        public static bool operator <=(SDate date, SDate other)
         {
-            if (s1.Year < s2.Year)
-                return true;
-            else if (s1.Year == s2.Year)
-            {
-                if (s1.Season == s2.Season && s1.Day <= s2.Day)
-                    return true;
-                else if (s1.Season == "spring" && s2.Season != "spring")
-                    return true;
-                if (s1.Season == "summer" && (s2.Season == "fall" || s2.Season == "winter"))
-                    return true;
-                if (s1.Season == "fall" && s2.Season == "winter")
-                    return true;
-            }
-
-            return false;
+            return date?.GetHashCode() <= other?.GetHashCode();
         }
 
-        /// <summary>
-        /// Greater than operator. Tests the date being greater than to each other
-        /// </summary>
-        /// <param name="s1">The first date being compared</param>
-        /// <param name="s2">The second date being compared</param>
-        /// <returns>If the dates are greater than</returns>
-        public static bool operator <(SDate s1, SDate s2)
+        /// <summary>Get whether one date is less than another.</summary>
+        /// <param name="date">The base date to compare.</param>
+        /// <param name="other">The other date to compare.</param>
+        public static bool operator <(SDate date, SDate other)
         {
-            if (s1.Year < s2.Year)
-                return true;
-            else if (s1.Year == s2.Year)
-            {
-                if (s1.Season == s2.Season && s1.Day < s2.Day)
-                    return true;
-                else if (s1.Season == "spring" && s2.Season != "spring")
-                    return true;
-                if (s1.Season == "summer" && (s2.Season == "fall" || s2.Season == "winter"))
-                    return true;
-                if (s1.Season == "fall" && s2.Season == "winter")
-                    return true;
-            }
-
-            return false;
+            return date?.GetHashCode() < other?.GetHashCode();
         }
 
-        /// <summary>
-        /// Overrides the equals function.
-        /// </summary>
+        /// <summary>Overrides the equals function.</summary>
         /// <param name="obj">Object being compared.</param>
         /// <returns>The equalaity of the object.</returns>
         public override bool Equals(object obj)
         {
-            return base.Equals(obj);
+            return obj is SDate other && this == other;
         }
 
-        /// <summary>
-        /// This returns the hashcode of the object
-        /// </summary>
-        /// <returns>The hashcode of the object.</returns>
+        /// <summary>Get a hash code which uniquely identifies a date.</summary>
         public override int GetHashCode()
         {
-            return base.GetHashCode();
+            // return the number of days since 01 spring Y1
+            int yearIndex = this.Year - 1;
+            return
+                yearIndex * this.DaysInSeason * this.SeasonsInYear
+                + this.GetSeasonIndex() * this.DaysInSeason
+                + this.Day;
         }
 
+
         /*********
         ** Private methods
         *********/
+        /// <summary>Get the current season index.</summary>
+        /// <exception cref="InvalidOperationException">The current season wasn't recognised.</exception>
+        private int GetSeasonIndex()
+        {
+            int index = Array.IndexOf(this.Seasons, this.Season);
+            if (index == -1)
+                throw new InvalidOperationException($"The current season '{this.Season}' wasn't recognised.");
+            return index;
+        }
+
         /// <summary>Get the real index in an array which should be treated as a two-way loop.</summary>
         /// <param name="index">The index in the looped array.</param>
         /// <param name="length">The number of elements in the array.</param>