csharp-language-ext-pipelines.cs

using System.Threading.Tasks;
using LanguageExt;
using Xunit;

namespace LanguageExtDemo
{

    public class Repository
    {
        public OptionAsync<string> GetName(int id)
        {
            if(id == 1)
                return "Jo";
            if(id == 2)
                return "Ruben";
            return OptionAsync<string>.None;
        }
    }

    public class HttpAgent
    {
        public EitherAsync<string,int> GetBalance(string name)
        {
            if(name == "Jo")
                return 1337;
            return $"Left: Balance not found for user: <{name}>";
        }
    }

    public class Handler
    {
        private readonly Repository _repo;
        private readonly HttpAgent _agent;

        public Handler(Repository repo, HttpAgent agent)
        {
            _repo = repo;
            _agent = agent;
        }

        public async Task<string> GetBalanceReport(int userID)
        {
            var result =
                _repo
                    .GetName(userID)
                    .Bind<(string name, EitherAsync<string, int> balance)>(
                        name => (name, _agent.GetBalance(name)))


                    //aaand finally something with the results:
                    .Match(
                    tuple => tuple.balance.Match(
                        balance => $"Balance for <{tuple.name}>: <{balance}>", 
                        left => left),
                    () => Task.FromResult($"None: User name not found for id <{userID}>"));

            return await (await result);
        }
    }

    public class EitherOptionPipelines
    {
        [Fact]
        public async Task EitherOptionAsyncPipelines()
        {
            var handler = new Handler(new Repository(), new HttpAgent());

            Assert.Equal("Balance for <Jo>: <1337>", await handler.GetBalanceReport(1));
            Assert.Equal("Left: Balance not found for user: <Ruben>", await handler.GetBalanceReport(2));
            Assert.Equal("None: User name not found for id <3>", await handler.GetBalanceReport(3));
        }
    }
}