[parsing] Add note visibility search query type (ISH-707)

Iceshrimp.Backend/Core/Extensions/QueryableFtsExtensions.cs

@@ -35,6 +35,7 @@ public static class QueryableFtsExtensions
 			InstanceFilter instanceFilter     => current.ApplyInstanceFilter(instanceFilter, config),
 			MentionFilter mentionFilter       => current.ApplyMentionFilter(mentionFilter, config, db),
 			MiscFilter miscFilter             => current.ApplyMiscFilter(miscFilter, user),
+			VisibilityFilter visibilityFilter => current.ApplyVisibilityFilter(visibilityFilter),
 			ReplyFilter replyFilter           => current.ApplyReplyFilter(replyFilter, config, db),
 			CwFilter cwFilter                 => current.ApplyCwFilter(cwFilter, caseSensitivity, matchType),
 			WordFilter wordFilter             => current.ApplyWordFilter(wordFilter, caseSensitivity, matchType),
@@ -163,6 +164,22 @@ public static class QueryableFtsExtensions
 		};
 	}
 
+	private static IQueryable<Note> ApplyVisibilityFilter(this IQueryable<Note> query, VisibilityFilter filter)
+	{
+		var visibility = filter.Value switch
+		{
+			VisibilityFilterType.Public    => Note.NoteVisibility.Public,
+			VisibilityFilterType.Home      => Note.NoteVisibility.Home,
+			VisibilityFilterType.Followers => Note.NoteVisibility.Followers,
+			VisibilityFilterType.Specified => Note.NoteVisibility.Specified,
+			_                              => throw new ArgumentOutOfRangeException()
+		};
+
+		return filter.Negated
+			? query.Where(p => p.Visibility != visibility)
+			: query.Where(p => p.Visibility == visibility);
+	}
+
 	[SuppressMessage("ReSharper", "EntityFramework.UnsupportedServerSideFunctionCall", Justification = "Projectables")]
 	private static IQueryable<Note> ApplyFollowersFilter(this IQueryable<Note> query, User user, bool negated)
 		=> query.Where(p => negated ? !p.User.IsFollowing(user) : p.User.IsFollowing(user));

Iceshrimp.Parsing/SearchQueryFilters.cs

@@ -131,6 +131,43 @@ public record AfterFilter(DateOnly Value) : ISearchQueryFilter;
 
 public record BeforeFilter(DateOnly Value) : ISearchQueryFilter;
 
+public enum VisibilityFilterType
+{
+	Public,
+	Home,
+	Followers,
+	Specified
+}
+
+public record VisibilityFilter(bool Negated, VisibilityFilterType Value) : ISearchQueryFilter
+{
+	public static bool TryParse(
+		bool negated, ReadOnlySpan<char> value, [NotNullWhen(true)] out VisibilityFilter? result
+	)
+	{
+		VisibilityFilterType? type = value switch
+		{
+			"public"    => VisibilityFilterType.Public,
+			"home"      => VisibilityFilterType.Home,
+			"unlisted"  => VisibilityFilterType.Home,
+			"followers" => VisibilityFilterType.Followers,
+			"specified" => VisibilityFilterType.Specified,
+			"direct"    => VisibilityFilterType.Specified,
+			"private"   => VisibilityFilterType.Specified,
+			_           => null
+		};
+
+		if (!type.HasValue)
+		{
+			result = null;
+			return false;
+		}
+
+		result = new VisibilityFilter(negated, type.Value);
+		return true;
+	}
+}
+
 public enum CaseFilterType
 {
 	Sensitive,

Iceshrimp.Parsing/SearchQueryParser.cs

@@ -84,6 +84,7 @@ public static class SearchQueryParser
 
 			"filter" when MiscFilter.TryParse(negated, value, out var parsed)           => parsed,
 			"in" when InFilter.TryParse(negated, value, out var parsed)                 => parsed,
+			"visibility" when VisibilityFilter.TryParse(negated, value, out var parsed) => parsed,
 			"has" or "attachment" or "attached" when AttachmentFilter.TryParse(negated, value, out var parsed)
 				=> parsed,