ErsatzTV/ErsatzTV.Application/MediaCollections/Commands/CreateCollectionHandler.cs

using ErsatzTV.Core;
using ErsatzTV.Core.Domain;
using ErsatzTV.Core.Interfaces.Search;
using ErsatzTV.Infrastructure.Data;
using Microsoft.EntityFrameworkCore;
using static ErsatzTV.Application.MediaCollections.Mapper;

namespace ErsatzTV.Application.MediaCollections;

public class CreateCollectionHandler :
    IRequestHandler<CreateCollection, Either<BaseError, MediaCollectionViewModel>>
{
    private readonly IDbContextFactory<TvContext> _dbContextFactory;
    private readonly ISearchTargets _searchTargets;

    public CreateCollectionHandler(IDbContextFactory<TvContext> dbContextFactory, ISearchTargets searchTargets)
    {
        _dbContextFactory = dbContextFactory;
        _searchTargets = searchTargets;
    }

    public async Task<Either<BaseError, MediaCollectionViewModel>> Handle(
        CreateCollection request,
        CancellationToken cancellationToken)
    {
        await using TvContext dbContext = await _dbContextFactory.CreateDbContextAsync(cancellationToken);
        Validation<BaseError, Collection> validation = await Validate(dbContext, request);
        return await validation.Apply(c => PersistCollection(dbContext, c));
    }

    private async Task<MediaCollectionViewModel> PersistCollection(TvContext dbContext, Collection collection)
    {
        await dbContext.Collections.AddAsync(collection);
        await dbContext.SaveChangesAsync();
        _searchTargets.SearchTargetsChanged();
        return ProjectToViewModel(collection);
    }

    private static Task<Validation<BaseError, Collection>> Validate(
        TvContext dbContext,
        CreateCollection request) =>
        ValidateName(dbContext, request).MapT(name => new Collection
        {
            Name = name,
            MediaItems = new List<MediaItem>()
        });

    private static async Task<Validation<BaseError, string>> ValidateName(
        TvContext dbContext,
        CreateCollection createCollection)
    {
        Validation<BaseError, string> result1 = createCollection.NotEmpty(c => c.Name)
            .Bind(_ => createCollection.NotLongerThan(50)(c => c.Name));

        bool duplicateName = await dbContext.Collections
            .AnyAsync(c => c.Name == createCollection.Name);

        Validation<BaseError, Unit> result2 = duplicateName
            ? Fail<BaseError, Unit>("Collection name must be unique")
            : Success<BaseError, Unit>(Unit.Default);

        return (result1, result2).Apply((_, _) => createCollection.Name);
    }
}