messengerapi.Broker/code/MessengerBroker/Handlers/DataHandler.cs

using MessengerApi.Db;
using MessengerBroker.Db;
using Microsoft.EntityFrameworkCore;

namespace MessengerBroker.Handlers
{
    public class DataHandler
    {
        private readonly Settings _settings;

        public Task<Tuple<MessengerApi.Db.Entities.User[], MessengerApi.Db.Entities.UserRoute[]>> GetLocalUsersAndRoutes()
        {
            var foreignUserIds = (Guid[])null;
            using(var broCtx = new BrokerDbContext(this._settings.MessengerBrokerDbConnectionString))
            {
                foreignUserIds = broCtx.Users.Select(x => x.Id).ToArray();
            }

            using (var apiCtx = new MessengerDbContext(this._settings.MessengerApiDbConnectionString))
            {
                var localUsers = apiCtx.Users
                    .Where(x => !foreignUserIds.Any(f => f == x.Id))
                    .ToArray();
                var localRoutes = apiCtx.UserRoutes
                    .Include(x => x.From)
                    .Include(x => x.To)
                    .Where(x => localUsers.Any(l => l.Id == x.From.Id) && localUsers.Any(l => l.Id == x.To.Id))
                    .ToArray();

                return Task.FromResult(new Tuple<MessengerApi.Db.Entities.User[], MessengerApi.Db.Entities.UserRoute[]>(
                    localUsers,
                    localRoutes));
            }
        }

        private Task<MessengerApi.Db.Entities.User[]> GetForeignUsers(Guid brokerId)
        {
            var foreignUserIds = (Guid[])null;
            using (var broCtx = new BrokerDbContext(this._settings.MessengerBrokerDbConnectionString))
            {
                foreignUserIds = broCtx.Users.Where(x=>x.BrokerId == brokerId).Select(x => x.Id).ToArray();
            }

            using (var apiCtx = new MessengerDbContext(this._settings.MessengerApiDbConnectionString))
            {
                var localUsers = apiCtx.Users
                    .Where(x => !foreignUserIds.Any(f => f == x.Id))
                    .ToArray();

                return Task.FromResult(localUsers);
            }
        }

        public async Task<MessengerApi.Db.Entities.Message[]> GetMessages(Guid brokerId, DateTime sinceUtc)
        {
            var userIds = (Guid[])null;

            if(brokerId == this._settings.BrokerId)
            {
                // Our messages.
                var users = await this.GetLocalUsersAndRoutes();
                userIds = users.Item1.Select(x => x.Id).ToArray();
            }
            else
            {
                var users = await this.GetForeignUsers(brokerId);
                userIds = users.Select(x => x.Id).ToArray();
            }

            using (var apiCtx = new MessengerDbContext(this._settings.MessengerApiDbConnectionString))
            {
                var messages = apiCtx.Messages
                    .Include(x => x.From).Include(x => x.To)
                    .Where(x => x.CreatedUtc >= sinceUtc && userIds.Contains(x.From.Id))
                    .ToArray();

                return messages;
            }
        }
    }
}