implement proper time zone converter

CompatBot/Commands/EventsBaseCommand.cs

@@ -304,15 +304,13 @@ namespace CompatBot.Commands
             }
             else if (txt != null)
             {
-                var newStartTime = FixTimeString(txt.Content);
-                if (!DateTime.TryParse(newStartTime, out var newTime))
+                if (!TimeParser.TryParse(txt.Content, out var newTime))
                 {
-                    errorMsg = $"Couldn't parse `{newStartTime}` as a start date and time";
+                    errorMsg = $"Couldn't parse `{txt.Content}` as a start date and time";
                     goto step1;
                 }
 
                 var duration = evt.End - evt.Start;
-                newTime = Normalize(newTime);
                 evt.Start = newTime.Ticks;
                 evt.End = evt.Start + duration;
                 evt.Year = newTime.Year;
@@ -487,25 +485,6 @@ namespace CompatBot.Commands
             return score > 0.5 ? name : eventName;
         }
 
-        private static string FixTimeString(string dateTime)
-        {
-            return dateTime.ToUpperInvariant()
-                .Replace("PST", "-08:00")
-                .Replace("EST", "-05:00")
-                .Replace("BST", "-03:00")
-                .Replace("JST", "+09:00")
-                .Replace("AEST", "+10:00");
-        }
-
-        private static DateTime Normalize(DateTime date)
-        {
-            if (date.Kind == DateTimeKind.Utc)
-                return date;
-            if (date.Kind == DateTimeKind.Local)
-                return date.ToUniversalTime();
-            return date.AsUtc();
-        }
-
         private static async Task<TimeSpan?> TryParseTimeSpanAsync(CommandContext ctx, string duration, bool react = true)
         {
             var d = Duration.Match(duration);

CompatBot/Utils/TimeParser.cs

@@ -0,0 +1,86 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Remotion.Linq.Clauses;
+
+namespace CompatBot.Utils
+{
+    public static class TimeParser
+    {
+        private static readonly Dictionary<string, TimeZoneInfo> TimeZoneMap;
+
+        static TimeParser()
+        {
+            var tzAcronyms = new Dictionary<string, string[]>
+            {
+                ["PT"] = new[] { "Pacific Standard Time" },
+                ["PST"] = new[] { "Pacific Standard Time" },
+                ["PDT"] = new[] { "Pacific Standard Time" },
+                ["EST"] = new[] { "Eastern Standard Time" },
+                ["EDT"] = new[] { "Eastern Standard Time" },
+                ["CEST"] = new[] { "Central European Standard Time" },
+                ["BST"] = new[] { "British Summer Time", "GMT Standard Time" },
+                ["JST"] = new[] { "Japan Standard Time", "Tokyo Standard Time" },
+            };
+            var uniqueNames = new HashSet<string>(
+                from tznl in tzAcronyms.Values
+                from tzn in tznl
+                select tzn
+            );
+            var tzList = TimeZoneInfo.GetSystemTimeZones();
+            var result = new Dictionary<string, TimeZoneInfo>();
+            foreach (var tzi in tzList)
+            {
+                if (uniqueNames.Contains(tzi.StandardName) || uniqueNames.Contains(tzi.StandardName))
+                {
+                    var acronyms = from tza in tzAcronyms
+                        where tza.Value.Contains(tzi.StandardName) || tza.Value.Contains(tzi.DaylightName)
+                        select tza.Key;
+                    foreach (var tza in acronyms)
+                        result[tza] = tzi;
+                }
+            }
+            TimeZoneMap = result;
+        }
+
+        public static bool TryParse(string dateTime, out DateTime result)
+        {
+            result = default;
+            if (string.IsNullOrEmpty(dateTime))
+                return false;
+
+            dateTime = dateTime.ToUpperInvariant();
+            if (char.IsDigit(dateTime[dateTime.Length - 1]))
+            {
+                return DateTime.TryParse(dateTime, out result);
+            }
+
+            var cutIdx = dateTime.LastIndexOf(' ');
+            if (cutIdx < 0)
+                return false;
+
+            var tza = dateTime.Substring(cutIdx + 1);
+            dateTime = dateTime.Substring(0, cutIdx);
+            if (TimeZoneMap.TryGetValue(tza, out var tzi))
+            {
+                if (!DateTime.TryParse(dateTime, out result))
+                    return false;
+
+                result = TimeZoneInfo.ConvertTimeToUtc(result, tzi);
+                return true;
+            }
+
+            return false;
+        }
+
+
+        public static DateTime Normalize(this DateTime date)
+        {
+            if (date.Kind == DateTimeKind.Utc)
+                return date;
+            if (date.Kind == DateTimeKind.Local)
+                return date.ToUniversalTime();
+            return date.AsUtc();
+        }
+    }
+}

Tests/TimeParserTests.cs

@@ -0,0 +1,20 @@
+using System;
+using CompatBot.Utils;
+using NUnit.Framework;
+
+namespace Tests
+{
+    [TestFixture]
+    public class TimeParserTests
+    {
+        [TestCase("2019-8-19 6:00 PT", "2019-08-19 13:00")]
+        [TestCase("2019-8-19 17:00 bst", "2019-08-19 16:00")]
+        public void TimeZoneConverterTest(string input, string utcInput)
+        {
+            var utc = DateTime.Parse(utcInput).Normalize();
+            Assert.That(TimeParser.TryParse(input, out var result), Is.True);
+            Assert.That(result, Is.EqualTo(utc));
+            Assert.That(result.Kind, Is.EqualTo(DateTimeKind.Utc));
+        }
+    }
+}