using System.Text.RegularExpressions;
using System.Threading;
using System.Threading.Tasks;
using ErsatzTV.Core;
using ErsatzTV.Core.Interfaces.Locking;
using ErsatzTV.Core.Interfaces.Repositories;
using ErsatzTV.Core.Interfaces.Search;
using ErsatzTV.Core.Interfaces.Trakt;
using ErsatzTV.Infrastructure.Data;
using LanguageExt;
using MediatR;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using Unit = LanguageExt.Unit;

namespace ErsatzTV.Application.MediaCollections.Commands
{
    public class AddTraktListHandler : TraktCommandBase, IRequestHandler<AddTraktList, Either<BaseError, Unit>>
    {
        private readonly IDbContextFactory<TvContext> _dbContextFactory;
        private readonly IEntityLocker _entityLocker;

        public AddTraktListHandler(
            ITraktApiClient traktApiClient,
            ISearchRepository searchRepository,
            ISearchIndex searchIndex,
            IDbContextFactory<TvContext> dbContextFactory,
            ILogger<AddTraktListHandler> logger,
            IEntityLocker entityLocker)
            : base(traktApiClient, searchRepository, searchIndex, logger)
        {
            _dbContextFactory = dbContextFactory;
            _entityLocker = entityLocker;
        }

        public async Task<Either<BaseError, Unit>> Handle(AddTraktList request, CancellationToken cancellationToken)
        {
            try
            {
                Validation<BaseError, Parameters> validation = ValidateUrl(request);
                return await validation.Match(
                    DoAdd,
                    error => Task.FromResult<Either<BaseError, Unit>>(error.Join()));
            }
            finally
            {
                _entityLocker.UnlockTrakt();
            }
        }
        
        private static Validation<BaseError, Parameters> ValidateUrl(AddTraktList request)
        {
            const string PATTERN = @"(?:https:\/\/trakt\.tv\/users\/)?([\w\-_]+)\/(?:lists\/)?([\w\-_]+)";
            Match match = Regex.Match(request.TraktListUrl, PATTERN);
            if (match.Success)
            {
                string user = match.Groups[1].Value;
                string list = match.Groups[2].Value;
                return new Parameters(user, list);
            }

            return BaseError.New("Invalid Trakt list url");
        }

        private async Task<Either<BaseError, Unit>> DoAdd(Parameters parameters)
        {
            await using TvContext dbContext = _dbContextFactory.CreateDbContext();
            
            return await TraktApiClient.GetUserList(parameters.User, parameters.List)
                .BindT(list => SaveList(dbContext, list))
                .BindT(list => SaveListItems(dbContext, list))
                .BindT(list => MatchListItems(dbContext, list))
                .MapT(_ => Unit.Default);
            
            // match list items (and update in search index)
        }

        private record Parameters(string User, string List);
    }
}