using PrivaPub.Federation.Actors;
using PrivaPub.Federation.Objects;
using PrivaPub.Infrastructure.Jobs;
using PrivaPub.Infrastructure.Statistics;
using PrivaPub.Models.Jobs;
using PrivaPub.Models.Statistics;
using PrivaPub.Models.User;

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

using static PrivaPub.Federation.Objects.ActivityJson;

namespace PrivaPub.Federation.Inbox
{
	public interface IActivityHandler
	{
		string Type { get; }
		Task Handle(JsonNode activity, ForeignAvatar actor, CancellationToken token);
	}

	public class InboxProcessor : IJobHandler
	{
		readonly IRemoteActorService _remoteActors;
		readonly IReadOnlyDictionary<string, IActivityHandler> _handlers;
		readonly ILogger<InboxProcessor> _logger;
		readonly IInteractionLedger _ledger;

		public InboxProcessor(IRemoteActorService remoteActors, IEnumerable<IActivityHandler> handlers, ILogger<InboxProcessor> logger,
			IInteractionLedger ledger = default)
		{
			_remoteActors = remoteActors;
			_handlers = handlers.ToDictionary(h => h.Type, StringComparer.Ordinal);
			_logger = logger;
			_ledger = ledger;
		}

		public JobKind Kind => JobKind.ProcessInbox;
		public int Concurrency => 2;
		public int MaxAttempts => 8;
		public int PerHostLimit => 2;

		public async Task<JobOutcome> Handle(Job job, CancellationToken token)
		{
			var started = Stopwatch.GetTimestamp();
			var payload = JsonSerializer.Deserialize<InboxPayload>(job.Payload);
			var activity = payload == default ? default : JsonNode.Parse(payload.Activity);
			var type = Value(activity, "type");
			if (type == default || !_handlers.TryGetValue(type, out var handler))
			{
				Record(job, payload, activity, type, started, new ArrivalVerdict(), Interactions.Dropped, "unknown-type");
				return JobOutcome.Done;
			}

			var actor = await _remoteActors.GetActor(payload.ActorURI, refresh: false, token);
			if (actor == default)
			{
				Record(job, payload, activity, type, started, new ArrivalVerdict(), Interactions.Deferred, "actor-unavailable");
				return JobOutcome.Retry("the actor could not be loaded");
			}

			var arrival = new Arrival(Id(activity), type, actor.ActorURI, payload.Inbox, payload.KeyId, payload.Algorithm,
				payload.SignedHeaders ?? Array.Empty<string>(), payload.ReceivedAt ?? job.CreatedAt, activity["@context"]?.ToJsonString());
			Arrival.Current = arrival;
			try
			{
				await handler.Handle(activity, actor, token);
			}
			catch (Exception ex) when (ex is not OperationCanceledException)
			{
				Record(job, payload, activity, type, started, arrival.Verdict, Interactions.Failed, ex.GetType().Name.ToLowerInvariant());
				throw;
			}
			finally
			{
				Arrival.Current = default;
			}
			Record(job, payload, activity, type, started, arrival.Verdict, default, default);
			_logger.LogInformation("Processed {Type} {Id} from {Actor}", type, Id(activity), actor.ActorURI);
			return JobOutcome.Done;
		}

		void Record(Job job, InboxPayload payload, JsonNode activity, string type, long started, ArrivalVerdict verdict, string outcome, string reason)
		{
			if (_ledger == default || payload == default)
				return;
			var embedded = activity?["object"] as JsonObject;
			_ledger.Record(new InteractionEvent
			{
				Channel = Interactions.In,
				Host = Interactions.HostOf(payload.ActorURI),
				Activity = type,
				Object = verdict.ObjectType ?? Value(embedded, "type"),
				Outcome = outcome ?? verdict.Outcome ?? Interactions.Accepted,
				Reason = reason ?? verdict.Reason,
				LatencyMs = (int)Stopwatch.GetElapsedTime(started).TotalMilliseconds,
				WaitMs = (int)Math.Min(int.MaxValue, Math.Max(0, (DateTime.UtcNow - (payload.ReceivedAt ?? job.CreatedAt)).TotalMilliseconds)),
				Attempt = job.Attempts,
				Audience = verdict.Audience ?? ActivityShape.Of(activity).Audience,
				LocalKind = verdict.LocalKind,
				AgeSeconds = verdict.AgeSeconds,
				Inbox = payload.Inbox,
				Signature = payload.Algorithm == default ? default : "cavage:" + payload.Algorithm,
				Features = type is "Create" or "Update" && embedded != default ? ObjectFeatures.Detect(embedded) : default
			}, payload.ActorURI);
		}
	}
}