using MessengerApi.Db;
using MessengerBroker.Db;
using Microsoft.EntityFrameworkCore;
using System.Text.Json;

namespace MessengerBroker.Handlers
{
    public class MasterHandler
    {
        private readonly Settings settings;

        private readonly HttpClient httpClient = new HttpClient();

        public async Task BeginSyncingWithMaster(Settings.MasterServer masterServer, CancellationToken ct = default)
        {
            while (!ct.IsCancellationRequested)
            {
                await Task.Delay(TimeSpan.FromSeconds(1));

                var usersRequest = new HttpRequestMessage(HttpMethod.Get, $"{masterServer.BrokerApiUrl}/users");
                usersRequest.Headers.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", this.settings.BrokerId.ToString());

                var usersResponseMessage = await this.httpClient.SendAsync(usersRequest, ct);

                if (!usersResponseMessage.IsSuccessStatusCode)
                {
                    continue;
                }

                var usersResponse = JsonSerializer.Deserialize<Model.Http.Users.UsersResponse>(await usersResponseMessage.Content.ReadAsStringAsync());

                using (var broCtx = new BrokerDbContext(this.settings.MessengerBrokerDbConnectionString))
                using (var apiCtx = new MessengerDbContext(this.settings.MessengerApiDbConnectionString))
                {
                    var updatedUsers = usersResponse.Users.Where(x => broCtx.Users.GetUserExists(x.Id)).ToList();
                    updatedUsers.ForEach(async x => await this.UpdateUser(x, apiCtx));

                    var deletedUsers = broCtx.Users.GetUsersExcept(usersResponse.Users.Select(x => x.Id)).ToList();
                    deletedUsers.ForEach(async x => await this.RemoveUser(x.Id, broCtx, apiCtx));

                    var addedUsers = usersResponse.Users.Where(x => !broCtx.Users.GetUserExists(x.Id)).ToList();
                    addedUsers.ForEach(async x => await this.AddUser(x, masterServer.BrokerId, broCtx, apiCtx));

                    foreach (var route in usersResponse.UserRoutes
                        .Where(r => apiCtx.UserRoutes
                            .Include(x => x.From)
                            .Include(x => x.To)
                            .Any(apir => apir.Id == r.Id && (apir.From.Id != r.FromId || apir.To.Id != r.ToId))))
                    {
                        var existing = apiCtx.UserRoutes.Include(x => x.From).Include(x => x.To).Single(x => x.Id == route.Id);
                        existing.From = apiCtx.Users.Single(x => x.Id == route.FromId);
                        existing.To = apiCtx.Users.Single(x => x.Id == route.ToId);
                    }

                    foreach (var deletedRoute in apiCtx.UserRoutes
                        .Where(x => !usersResponse.UserRoutes.Any(r => r.Id == x.Id)))
                    {
                        apiCtx.UserRoutes.Remove(deletedRoute);
                    }

                    foreach (var addedRoute in usersResponse.UserRoutes
                        .Where(r => !apiCtx.UserRoutes.Any(x => x.Id == r.Id)))
                    {
                        apiCtx.UserRoutes.Add(new MessengerApi.Db.Entities.UserRoute
                        {
                            Id = addedRoute.Id,
                            From = apiCtx.Users.Single(x => x.Id == addedRoute.FromId),
                            To = apiCtx.Users.Single(x => x.Id == addedRoute.ToId)
                        });
                    }

                    broCtx.SaveChanges();
                    apiCtx.SaveChanges();
                }

                var messagesRequest = new HttpRequestMessage(HttpMethod.Get, $"{masterServer.BrokerApiUrl}/messages");
                messagesRequest.Headers.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", this.settings.BrokerId.ToString());

                var messagesResponseMessage = await this.httpClient.SendAsync(messagesRequest, ct);

                if (!messagesResponseMessage.IsSuccessStatusCode)
                {
                    continue;
                }

                var messagesResponse = JsonSerializer.Deserialize<Model.Http.Sync.SyncResponse>(await messagesResponseMessage.Content.ReadAsStringAsync());

                using (var broCtx = new BrokerDbContext(this.settings.MessengerBrokerDbConnectionString))
                using (var apiCtx = new MessengerDbContext(this.settings.MessengerApiDbConnectionString))
                {
                    var addedMessages = messagesResponse.Messages
                        .Where(m => broCtx.Messages.Any(x => x.BrokerId == masterServer.BrokerId && x.Id == m.Id) == false)
                        .ToList();

                    addedMessages.ForEach(x =>
                    {
                        broCtx.Messages.Add(new Db.Model.Message
                        {
                            BrokerId = masterServer.BrokerId,
                            Id = x.Id
                        });

                        apiCtx.Messages.Add(new MessengerApi.Db.Entities.Message
                        {
                            Id = x.Id,
                            CreatedUtc = x.CreatedUtc,
                            From = x.From != null ? (apiCtx.Users.SingleOrDefault(u => u.Id == x.From.Value)) ?? null : null,
                            To = x.To != null ? (apiCtx.Users.SingleOrDefault(u => u.Id == x.To.Value)) ?? null : null,
                            IsAcknowledged = x.IsAcknowledged,
                            IsDelivered = x.IsDelivered,
                            Payload = x.Payload,
                            PayloadId = x.PayloadId,
                            PayloadLifespanInSeconds = x.PayloadLifespanInSeconds,
                            PayloadTimestamp = x.PayloadTimestamp,
                            PayloadType = x.PayloadType,
                        });
                    });

                    var existingMessages = messagesResponse.Messages
                        .Except(addedMessages)
                        .ToList();

                    existingMessages.ForEach(x =>
                    {
                        var existing = apiCtx.Messages.SingleOrDefault(a => a.Id ==  x.Id);

                        if(existing != null && (existing.IsDelivered != x.IsDelivered || existing.IsAcknowledged != x.IsAcknowledged))
                        {
                            existing.IsDelivered = x.IsDelivered;
                            existing.IsAcknowledged = x.IsAcknowledged;
                        }
                    });

                    broCtx.SaveChanges();
                    apiCtx.SaveChanges();
                }
            }
        }

        private async Task RemoveUser(Guid id, BrokerDbContext broCtx, MessengerDbContext apiCtx)
        {
            var broUser = await broCtx.Users.SingleOrDefaultAsync(x => x.Id == id);

            if (broUser != null)
            {
                broCtx.Users.Remove(broUser);
            }

            var apiUser = await apiCtx.Users.SingleOrDefaultAsync(x => x.Id == id);

            if (apiUser != null)
            {
                apiCtx.Users.Remove(apiUser);
            }
        }

        private async Task AddUser(Model.Http.Users.UsersResponse.User user, Guid brokerId, BrokerDbContext broCtx, MessengerDbContext apiCtx)
        {
            if (broCtx.Users.GetUserExists(user.Id) == false)
            {
                broCtx.Users.Add(new Db.Model.User
                {
                    Id = user.Id,
                    BrokerId = brokerId
                });
            }

            if (apiCtx.Users.Any(x => x.Id == user.Id))
            {
                await this.UpdateUser(user, apiCtx);
            }
            else
            {
                await apiCtx.Users.AddAsync(new MessengerApi.Db.Entities.User
                {
                    Id = user.Id,
                    ApiKey = user.ApiKey,
                    CanReceive = user.CanReceive,
                    CanSend = user.CanSend,
                    IsEnabled = user.IsEnabled,
                    Name = user.Name
                });
            }
        }

        private async Task UpdateUser(Model.Http.Users.UsersResponse.User user, MessengerDbContext apiCtx)
        {
            var apiUser = await apiCtx.Users.SingleAsync(x => x.Id == user.Id);
            apiUser.ApiKey = user.ApiKey;
            apiUser.CanReceive = user.CanReceive;
            apiUser.CanSend = user.CanSend;
            apiUser.IsEnabled = user.IsEnabled;
            apiUser.Name = user.Name;
        }
    }
}