using System.Diagnostics.CodeAnalysis;
using Iceshrimp.Backend.Core.Configuration;
using Iceshrimp.Backend.Core.Database;
using Iceshrimp.Backend.Core.Database.Tables;
using Iceshrimp.Backend.Core.Federation.ActivityStreams;
using Iceshrimp.Backend.Core.Federation.ActivityStreams.Types;
using Iceshrimp.Backend.Core.Services;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Options;
using Newtonsoft.Json.Linq;
using J = System.Text.Json.Serialization.JsonPropertyNameAttribute;
using JR = System.Text.Json.Serialization.JsonRequiredAttribute;

namespace Iceshrimp.Backend.Core.Queues;

public class PreDeliverQueue()
	: PostgresJobQueue<PreDeliverJobData>("pre-deliver", PreDeliverQueueProcessorDelegateAsync, 4)
{
	private static async Task PreDeliverQueueProcessorDelegateAsync(
		Job job, PreDeliverJobData jobData, IServiceProvider scope, CancellationToken token
	)
	{
		var logger   = scope.GetRequiredService<ILogger<DeliverQueue>>();
		var db       = scope.GetRequiredService<DatabaseContext>();
		var queueSvc = scope.GetRequiredService<QueueService>();
		var config   = scope.GetRequiredService<IOptionsSnapshot<Config.SecuritySection>>();

		var parsed       = JToken.Parse(jobData.SerializedActivity);
		var expanded     = LdHelpers.Expand(parsed) ?? throw new Exception("Failed to expand activity");
		var deserialized = ASObject.Deserialize(expanded);
		if (deserialized is not ASActivity activity)
			throw new Exception("Deserialized ASObject is not an activity");

		if (jobData.DeliverToFollowers)
			logger.LogDebug("Delivering activity {id} to followers", activity.Id);
		else
			logger.LogDebug("Delivering activity {id} to specified recipients", activity.Id);

		if (activity.Actor == null) throw new Exception("Actor must not be null");

		if (jobData is { DeliverToFollowers: false, RecipientIds.Count: < 1 })
			return;

		var query = jobData.DeliverToFollowers
			? db.Followings.Where(p => p.FolloweeId == jobData.ActorId)
			    .Select(p => new InboxQueryResult
			    {
				    InboxUrl = p.FollowerSharedInbox ?? p.FollowerInbox, Host = p.FollowerHost
			    })
			: db.Users.Where(p => jobData.RecipientIds.Contains(p.Id))
			    .Select(p => new InboxQueryResult { InboxUrl = p.SharedInbox ?? p.Inbox, Host = p.Host });

		// We want to deliver activities to the explicitly specified recipients first
		if (jobData is { DeliverToFollowers: true, RecipientIds.Count: > 0 })
		{
			query = db.Users.Where(p => jobData.RecipientIds.Contains(p.Id))
			          .Select(p => new InboxQueryResult { InboxUrl = p.SharedInbox ?? p.Inbox, Host = p.Host })
			          .Concat(query);
		}

		var inboxQueryResults = await query.Where(p => p.InboxUrl != null && p.Host != null)
		                                   .Distinct()
		                                   .ToListAsync(token);

		if (inboxQueryResults.Count == 0) return;

		string payload;
		if (config.Value.AttachLdSignatures)
		{
			var keypair = await db.UserKeypairs.FirstAsync(p => p.UserId == jobData.ActorId, token);
			payload = await activity.SignAndCompactAsync(keypair);
		}
		else
		{
			payload = activity.Compact();
		}

		foreach (var inboxQueryResult in inboxQueryResults)
			await queueSvc.DeliverQueue.EnqueueAsync(new DeliverJobData
			{
				RecipientHost =
					inboxQueryResult.Host ??
					throw new Exception("Recipient host must not be null"),
				InboxUrl =
					inboxQueryResult.InboxUrl ??
					throw new
						Exception("Recipient inboxUrl must not be null"),
				Payload     = payload,
				ContentType = "application/activity+json",
				UserId      = jobData.ActorId
			});
	}

	private class InboxQueryResult : IEquatable<InboxQueryResult>
	{
		public required string? Host;
		public required string? InboxUrl;

		public bool Equals(InboxQueryResult? other)
		{
			if (ReferenceEquals(null, other)) return false;
			if (ReferenceEquals(this, other)) return true;
			return InboxUrl == other.InboxUrl && Host == other.Host;
		}

		public override bool Equals(object? obj)
		{
			if (ReferenceEquals(null, obj)) return false;
			if (ReferenceEquals(this, obj)) return true;
			if (obj.GetType() != GetType()) return false;
			return Equals((InboxQueryResult)obj);
		}

		[SuppressMessage("ReSharper", "NonReadonlyMemberInGetHashCode", Justification =
			                 "We are using this as a Tuple that works with LINQ on our IQueryable iterator. This is therefore intended behavior.")]
		public override int GetHashCode()
		{
			return HashCode.Combine(InboxUrl, Host);
		}

		public static bool operator ==(InboxQueryResult? left, InboxQueryResult? right)
		{
			return Equals(left, right);
		}

		public static bool operator !=(InboxQueryResult? left, InboxQueryResult? right)
		{
			return !Equals(left, right);
		}
	}
}

public class PreDeliverJobData : Job
{
	[JR] [J("serializedActivity")] public required string       SerializedActivity { get; set; }
	[JR] [J("actorId")]            public required string       ActorId            { get; set; }
	[JR] [J("recipientIds")]       public required List<string> RecipientIds       { get; set; }
	[JR] [J("deliverToFollowers")] public required bool         DeliverToFollowers { get; set; }
}