mastodon-backup-filter/MastodonBackup.cs

using System.Text.Json;
using System.Text.Json.Nodes;

namespace MastodonBackupFilter
{
    public class MastodonBackup {

    public static Task<MastodonBackup> FromFileAsync(FileInfo? filename){

        if (filename is null || !filename.Exists)
        {
            throw new FileNotFoundException($"File doesn't exist: {filename?.FullName}");
        }

        Console.WriteLine($"Reading {filename.FullName}");

        var options = new JsonSerializerOptions { WriteIndented = true };

        using var jsonStream = filename.OpenRead();
        var root = JsonNode.Parse(jsonStream);

        var items = root!["orderedItems"].AsArray().ToArray();//.Take(150).ToArray();

        Console.WriteLine($"{items.Length} posts");

        var keysToRemove = new Stack<uint>();
        var visibilityCounters = new Dictionary<Visibility, uint>();

        for (var i = 0; i < items.Length; i++)
        {
            var item = items[i];

            var mastodonObject = MastodonOutboxNodeReader.ReadNodes(item);

            var msg = mastodonObject switch {
                CreateActivityJsonNode create => $"tooted {create.Payload switch {
                    NoteObject n => $"toot {n.Url} to {n.Recipients} {(n.Recipients != create.Recipients ? $"(create activity recipients differ: {create.Recipients}" : "")}",
                    MastodonObject idk => $"other object with id {idk.Id}",
                    _ => throw new InvalidDataException("shouldn't happen")
                }}",
                AnnounceActivityJsonNode<string> announce => $"boosted {announce.BoostTarget} to {announce.Recipients}",
                AnnounceActivityJsonNode<UrlObject> announce => $"boosted {announce.BoostTarget.Url} to {announce.Recipients}",
                MastodonObject idk => $"some unhandled kind of object with id {idk.Id}",
                _ => throw new InvalidDataException("shouldn't happen")
            };

            try {
                var vis = (mastodonObject as OutboxObject).Visibility;
                Console.WriteLine($"{msg} {vis}");

                if (visibilityCounters.TryGetValue(vis, out uint vCount)) {
                    visibilityCounters[vis] = vCount + 1;
                } else {
                    visibilityCounters[vis] = 1;
                }
            }
            catch (Exception ex) {
                Console.WriteLine(msg);
                Console.WriteLine($"Failed to determine visibility for object: {ex}");
                throw;
            }

        }

        foreach (var k in visibilityCounters.Keys){
            Console.WriteLine($"{k}: {visibilityCounters[k]}");
        }

        return Task.FromResult(new MastodonBackup {});
    }
}
}