Add system time zone command

PluralKit.Bot/Commands/SystemCommands.cs

@@ -1,9 +1,14 @@
 using System;
 using System.Linq;
 using System.Runtime.Serialization;
+using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using Dapper;
 using Discord.Commands;
+using NodaTime;
+using NodaTime.Extensions;
+using NodaTime.Text;
+using NodaTime.TimeZones;
 
 namespace PluralKit.Bot.Commands
 {
@@ -140,6 +145,32 @@ namespace PluralKit.Bot.Commands
             }
         }
 
+        [Command("timezone")]
+        [Remarks("system timezone [timezone]")]
+        public async Task SystemTimezone([Remainder] string zoneStr = null)
+        {
+            if (zoneStr == null)
+            {
+                Context.SenderSystem.UiTz = "UTC";
+                await Systems.Save(Context.SenderSystem);
+                await Context.Channel.SendMessageAsync($"{Emojis.Success} System time zone cleared.");
+                return;
+            }
+
+            var zones = DateTimeZoneProviders.Tzdb;
+            var zone = zones.GetZoneOrNull(zoneStr);
+            if (zone == null) throw Errors.InvalidTimeZone(zoneStr);
+
+            var currentTime = SystemClock.Instance.GetCurrentInstant().InZone(zone);
+            var msg = await Context.Channel.SendMessageAsync(
+                $"This will change the system time zone to {zone.Id}. The current time is {currentTime.ToString(Formats.DateTimeFormat, null)}. Is this correct?");
+            if (!await Context.PromptYesNo(msg)) throw Errors.TimezoneChangeCancelled;
+            Context.SenderSystem.UiTz = zone.Id;
+            await Systems.Save(Context.SenderSystem);
+
+            await Context.Channel.SendMessageAsync($"System time zone changed to {zone.Id}.");
+        }
+
         public override async Task<PKSystem> ReadContextParameterAsync(string value)
         {
             var res = await new PKSystemTypeReader().ReadAsync(Context, value, _services);

PluralKit.Bot/Errors.cs

@@ -56,5 +56,9 @@ namespace PluralKit.Bot {
         public static PKError SwitchMoveBeforeSecondLast(ZonedDateTime time) => new PKError($"Can't move switch to before last switch time ({time.ToString(Formats.DateTimeFormat, null)}), as it would cause conflicts.");
         public static PKError SwitchMoveCancelled => new PKError("Switch move cancelled.");
         public static PKError SwitchDeleteCancelled => new PKError("Switch deletion cancelled.");
+        public static PKError TimezoneParseError(string timezone) => new PKError($"Could not parse timezone offset {timezone}. Offset must be a value like 'UTC+5' or 'GMT-4:30'.");
+
+        public static PKError InvalidTimeZone(string zoneStr) => new PKError($"Invalid time zone ID '{zoneStr}'. To find your time zone ID, use the following website: <https://xske.github.io/tz>");
+        public static PKError TimezoneChangeCancelled => new PKError("Time zone change cancelled.");
     }
 }

PluralKit.Core/Utils.cs

@@ -206,7 +206,7 @@ namespace PluralKit
 
     public static class Formats
     {
-        public static string DateTimeFormat = "yyyy-MM-dd HH-mm-ss";
+        public static string DateTimeFormat = "yyyy-MM-dd HH:mm:ss";
         public static string DurationFormat = "D'd' h'h' m'm' s's'";
     }
 }