refactor: move ContextExts to own folder, CommandTree / command defs to CommandMeta folder

PluralKit.Bot/CommandSystem/Context/ContextAvatarExt.cs

@@ -0,0 +1,61 @@
+#nullable enable
+using Myriad.Extensions;
+using Myriad.Types;
+
+namespace PluralKit.Bot;
+
+public static class ContextAvatarExt
+{
+    public static async Task<ParsedImage?> MatchImage(this Context ctx)
+    {
+        // If we have a user @mention/ID, use their avatar
+        if (await ctx.MatchUser() is { } user)
+        {
+            var url = user.AvatarUrl("png", 256);
+            return new ParsedImage { Url = url, Source = AvatarSource.User, SourceUser = user };
+        }
+
+        // If we have a positional argument, try to parse it as a URL
+        var arg = ctx.RemainderOrNull();
+        if (arg != null)
+        {
+            // Allow surrounding the URL with <angle brackets> to "de-embed"
+            if (arg.StartsWith("<") && arg.EndsWith(">"))
+                arg = arg.Substring(1, arg.Length - 2);
+
+            if (!Uri.TryCreate(arg, UriKind.Absolute, out var uri))
+                throw Errors.InvalidUrl(arg);
+
+            if (uri.Scheme != "http" && uri.Scheme != "https")
+                throw Errors.InvalidUrl(arg);
+
+            // ToString URL-decodes, which breaks URLs to spaces; AbsoluteUri doesn't
+            return new ParsedImage { Url = uri.AbsoluteUri, Source = AvatarSource.Url };
+        }
+
+        // If we have an attachment, use that
+        if (ctx.Message.Attachments.FirstOrDefault() is { } attachment)
+        {
+            var url = attachment.ProxyUrl;
+            return new ParsedImage { Url = url, Source = AvatarSource.Attachment };
+        }
+
+        // We should only get here if there are no arguments (which would get parsed as URL + throw if error)
+        // and if there are no attachments (which would have been caught just before)
+        return null;
+    }
+}
+
+public struct ParsedImage
+{
+    public string Url;
+    public AvatarSource Source;
+    public User? SourceUser;
+}
+
+public enum AvatarSource
+{
+    Url,
+    User,
+    Attachment
+}