mastodon-backup-filter/VisibilityExtractor.cs

using System.Text.Json.Nodes;

namespace MastodonBackupFilter
{
    public class VisibilityExtractor
    {
        private static bool IsRecipientFollowers(JsonNode? recipientNode)
        {
            if (recipientNode is null)
            {
                return false;
            }

            try
            {

                var val = recipientNode.GetValue<string>();

                var recipientIsFollowers = val.EndsWith("/followers");
                return recipientIsFollowers;
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Mismatch, unexpected recipient node: {recipientNode}");
                return false;
            }
        }

        private static bool IsRecipientPublic(JsonNode? recipientNode)
        {
            if (recipientNode is null)
            {
                return false;
            }

            try
            {

                var val = recipientNode.GetValue<string>();

                var recipientIsPublic = val == "https://www.w3.org/ns/activitystreams#Public";
                return recipientIsPublic;
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Mismatch, unexpected recipient node: {recipientNode}");
                return false;
            }
        }
        public static PostRecipients ExtractRecipients(JsonNode node)
        {
            var to = node["to"].AsArray();
            var cc = node["cc"].AsArray();
            var recipients = to.Concat(cc).ToArray();

            return new PostRecipients {
                ToPublic = to.Where(r => IsRecipientPublic(r)).Any(),
                CcPublic = cc.Where(r => IsRecipientPublic(r)).Any(),
                ToFollowers = to.Where(r => IsRecipientFollowers(r)).Any(),
                CcFollowers = cc.Where(r => IsRecipientFollowers(r)).Any(),
            };
        }
    }
}