Musify/backend/Tests/Musify.Application.Tests/Mixes/GenerateMixesForUserCommandHandlerTests.cs

using Microsoft.EntityFrameworkCore;
using Musify.Application.Mixes;
using Musify.Application.Tests.TestSupport;
using Musify.Domain.Entities;
using Xunit;

namespace Musify.Application.Tests.Mixes
{
    public sealed class GenerateMixesForUserCommandHandlerTests : HandlerTestBase
    {
        private GenerateMixesForUserCommandHandler CreateHandler() => new(
            Database, TestConfigurations.Mix(), NoOpLogger<GenerateMixesForUserCommandHandler>());

        [Fact]
        public async Task Handle_NoTracks_DoesNotCreateAnyMix()
        {
            var user = TestEntities.User();
            await SeedAsync(user);

            var result = await CreateHandler().Handle(new GenerateMixesForUserCommand(user.Id), TestContext.Current.CancellationToken);

            Assert.False(result.IsError);
            Assert.Empty(await Database.Mixes.ToListAsync(TestContext.Current.CancellationToken));
        }

        [Fact]
        public async Task Handle_AllTracksAlreadyListenedTo_CreatesOnlyTheDailyMix()
        {
            var user = TestEntities.User();
            var track = TestEntities.Track(user);
            await SeedAsync(
                user, track,
                new UserHasTrack { UserId = user.Id, TrackId = track.Id },
                TestEntities.ListeningHistory(user.Id, track.Id));

            var result = await CreateHandler().Handle(new GenerateMixesForUserCommand(user.Id), TestContext.Current.CancellationToken);

            Assert.False(result.IsError);
            var mixes = await Database.Mixes.ToListAsync(TestContext.Current.CancellationToken);
            Assert.Single(mixes);
            Assert.Equal("Tu mezcla diaria", mixes[0].Title);
        }

        [Fact]
        public async Task Handle_UnheardTracksInLibrary_CreatesDiscoveryAndDailyMixes_AndReplacesPreviousMixes()
        {
            var user = TestEntities.User();
            var listenedTrack = TestEntities.Track(user, "Listened Track");
            var unheardTrack = TestEntities.Track(user, "Unheard Track");

            var staleMix = TestEntities.Mix(user.Id, "Stale Mix");
            var staleItem = TestEntities.MixItem(staleMix.Id, listenedTrack.Id);

            await SeedAsync(
                user, listenedTrack, unheardTrack, staleMix, staleItem,
                new UserHasTrack { UserId = user.Id, TrackId = listenedTrack.Id },
                new UserHasTrack { UserId = user.Id, TrackId = unheardTrack.Id },
                TestEntities.ListeningHistory(user.Id, listenedTrack.Id));

            var result = await CreateHandler().Handle(new GenerateMixesForUserCommand(user.Id), TestContext.Current.CancellationToken);

            Assert.False(result.IsError);
            var mixes = await Database.Mixes.ToListAsync(TestContext.Current.CancellationToken);
            Assert.DoesNotContain(mixes, mix => mix.Title == "Stale Mix");
            Assert.Contains(mixes, mix => mix.Title == "Descubrimiento");
            Assert.Contains(mixes, mix => mix.Title == "Tu mezcla diaria");
            Assert.Empty(await Database.MixItems.Where(item => item.MixId == staleMix.Id).ToListAsync(TestContext.Current.CancellationToken));

            var discoveryMix = mixes.Single(mix => mix.Title == "Descubrimiento");
            var discoveryItems = await Database.MixItems
                .Where(item => item.MixId == discoveryMix.Id)
                .ToListAsync(TestContext.Current.CancellationToken);
            Assert.All(discoveryItems, item => Assert.Equal(unheardTrack.Id, item.TrackId));
        }
    }
}