Couchbase Mapping Idea

CoucnbaseMappingTests.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using Couchbase.Lite;
using Couchbase.Lite.Mapping;
using FluentAssertions;
using NUnit.Framework;

// ReSharper disable TailRecursiveCall
// because the recursive call is easier to read ;)

namespace SomeMagicalNamespace
{
    [TestFixture]
    public class CouchbaseMappingTests
    {
        private readonly IMappingProvider _mappingProvider;

        public CouchbaseMappingTests()
        {
            _mappingProvider = new MappingProvider();

            MappingProvider.Configure(opts =>
                                      {
                                          opts.AddMapping<PersonMap>()
                                              .AddMapping<AddressMap>()
                                              .AddMapping<PetMap>();
                                      });
        }

        [Test]
        public void ShouldMapComplexObject()
        {
            // arrange
            var person = PersonFixture.JohnSmith;

            // act
            var dictionaryObject = person.ToMutableDocument();

            // assert
            dictionaryObject["firstName"]
               .Value
               .Should()
               .Be(PersonFixture.JohnSmith.FirstName);

            dictionaryObject["lastName"]
               .Value
               .Should()
               .Be(PersonFixture.JohnSmith.LastName);

            dictionaryObject["address"]["street"]
               .Value
               .Should()
               .Be(PersonFixture.JohnSmith.Address.Street);

            dictionaryObject["address"]["postalCode"]
               .Value
               .Should()
               .Be(PersonFixture.JohnSmith.Address.PostalCode);
        }

        [Test]
        public void ShouldMapBasicObject()
        {
            // arrange
            var pet = PetFixture.Fido;

            // act
            var dictionaryObject = pet.ToMutableDocument();

            // assert
            dictionaryObject["breed"]
               .String
               .Should()
               .Be(PetFixture.Fido.Breed);

            dictionaryObject["name"]
               .String
               .Should()
               .Be(PetFixture.Fido.Name);
        }

        [Test]
        public void ShouldMapBasicObjectWithMap()
        {
            // arrange
            var map = _mappingProvider.GetMap<Pet>();
            var pet = PetFixture.Fido;

            // act
            var dictionaryObject = pet.ToMutableDocument(map);

            // assert
            dictionaryObject["b"]
               .String
               .Should()
               .Be(PetFixture.Fido.Breed);

            dictionaryObject["n"]
               .String
               .Should()
               .Be(PetFixture.Fido.Name);
        }

        [Test]
        public void ShouldMapBasicDictionary()
        {
            // arrange
            var dict = new MutableDocument(new Dictionary<string, object>
                                               {
                                                   {"breed", PetFixture.Fido.Breed},
                                                   {"name", PetFixture.Fido.Name}
                                               });

            // act
            var pet = dict.ToObject<Pet>();

            // assert
            pet.Name.Should()
               .Be(PetFixture.Fido.Name);

            pet.Breed.Should()
               .Be(PetFixture.Fido.Breed);
        }

        [Test]
        public void ShouldMapBasicDictionaryWithMap()
        {
            // arrange
            var dict = new MutableDocument(new Dictionary<string, object>
                                               {
                                                   {"b", PetFixture.Fido.Breed},
                                                   {"n", PetFixture.Fido.Name}
                                               });

            // act
            var pet = dict.ToObject<Pet>();

            // assert
            pet.Name.Should()
               .Be(PetFixture.Fido.Name);

            pet.Breed.Should()
               .Be(PetFixture.Fido.Breed);
        }

        [Test]
        public void ShouldMapBasicDictionaryWithAttributeMap()
        {
            // arrange
            var dict = new MutableDocument(new Dictionary<string, object>
                                               {
                                                   {"Mk", VehicleFixture.ToyotaTundra.Make},
                                                   {"Mdl", VehicleFixture.ToyotaTundra.Model}
                                               });

            // act
            var vehicle = dict.ToObject<Vehicle>();

            // assert
            vehicle.Make.Should()
                   .Be(VehicleFixture.ToyotaTundra.Make);

            vehicle.Model.Should()
                   .Be(VehicleFixture.ToyotaTundra.Model);
        }

        [Test]
        public void ShouldMapComplexObjectWithMap()
        {
            // arrange
            var map = _mappingProvider.GetMap<Person>();
            var person = PersonFixture.JohnSmith;

            // act
            var dictionaryObject = person.ToMutableDocument(map);

            // assert
            dictionaryObject["fn"]
               .Value
               .Should()
               .Be(PersonFixture.JohnSmith.FirstName);

            dictionaryObject["ln"]
               .Value
               .Should()
               .Be(PersonFixture.JohnSmith.LastName);

            dictionaryObject["addr"]["st"]
               .Value
               .Should()
               .Be(PersonFixture.JohnSmith.Address.Street);

            dictionaryObject["addr"]["pc"]
               .Value
               .Should()
               .Be(PersonFixture.JohnSmith.Address.PostalCode);
        }

        [Test]
        public void ShouldMapComplexDictionaryWithMap()
        {
            throw new NotImplementedException();
        }

        [Test]
        public void ShouldMapComplexDictionary()
        {
            // arrange
            var dict = new MutableDocument(new Dictionary<string, object>
                                               {
                                                   {"firstName", PersonFixture.JohnSmith.FirstName},
                                                   {"lastName", PersonFixture.JohnSmith.LastName},
                                                   {
                                                       "address", new Dictionary<string, object>
                                                                      {
                                                                          {"street", PersonFixture.JohnSmith.Address.Street},
                                                                          {"postalCode", PersonFixture.JohnSmith.Address.PostalCode}
                                                                      }
                                                   }
                                               });

            // act
            var person = dict.ToObject<Person>();

            // assert
            person.FirstName.Should()
                  .Be(PersonFixture.JohnSmith.FirstName);

            person.LastName.Should()
                  .Be(PersonFixture.JohnSmith.LastName);

            person.Address.Street.Should()
                  .Be(PersonFixture.JohnSmith.Address.Street);

            person.Address.PostalCode.Should()
                  .Be(PersonFixture.JohnSmith.Address.PostalCode);
        }
    }

    public interface IMappingProvider
    {
        IPropertyNameConverter GetMap<T>() where T : class;
    }

    public sealed class MappingProvider : IMappingProvider
    {
        private static MappingOptions __mappingOptions;

        public static void Configure(Action<MappingOptions> action)
        {
            if (__mappingOptions != null)
            {
                throw new InvalidOperationException("You can only configure your mapping one time.");
            }

            var provider = new MappingProvider();
            __mappingOptions = new MappingOptions(provider);
            action.Invoke(__mappingOptions);
        }

        public IPropertyNameConverter GetMap<T>() where T : class => GetMap(typeof(T).Name);

        public IPropertyNameConverter GetMap(string objectPropertyName)
        {
            if (__mappingOptions is null)
            {
                throw new InvalidOperationException("You must configure your mapping before trying to acquire a map.");
            }

            return __mappingOptions.GetMap(objectPropertyName);
        }
    }

    public sealed class MappingOptions
    {
        private readonly MappingProvider _mappingProvider;
        private readonly Dictionary<string, Mapping> _mappings = new Dictionary<string, Mapping>();

        public MappingOptions(MappingProvider mappingProvider) => _mappingProvider = mappingProvider;

        public MappingOptions AddMapping<T>() where T : Mapping
        {
            var mapping = (T) Activator.CreateInstance(typeof(T), _mappingProvider);
            _mappings[mapping.ObjectTypeName] = mapping;

            return this;
        }

        public IPropertyNameConverter GetMap<T>() => GetMap(typeof(T).Name);
        public IPropertyNameConverter GetMap(string objectTypeName) => _mappings[objectTypeName];
    }

    public abstract class Mapping : IPropertyNameConverter
    {
        protected Mapping(MappingProvider mappingProvider) => _mappingProvider = mappingProvider;
        protected readonly HashSet<(string objectPropetyName, string documentPropertyName)> PropertyMap = new HashSet<(string objectPropetyName, string documentPropertyName)>();
        private readonly Dictionary<(string objectPropetyName, string documentPropertyName), Mapping> _childMaps = new Dictionary<(string objectPropetyName, string documentPropertyName), Mapping>();
        public string ObjectTypeName { get; protected set; }

        public string Convert(string val)
        {
            var propertyMap = PropertyMap.FirstOrDefault(x => x.objectPropetyName == val);

            if (propertyMap != default)
            {
                return propertyMap.documentPropertyName;
            }

            // mapping must be on a complex object
            var childMapping = _mappingProvider.GetMap(val);

            // how do we access complex child objects?
            throw new NotImplementedException();
        }

        private readonly MappingProvider _mappingProvider;
    }

    public abstract class Mapping<T> : Mapping where T : class
    {
        protected Mapping(MappingProvider mappingProvider) : base(mappingProvider) => ObjectTypeName = typeof(T).Name;

        protected void MappingFor(Expression<Func<T, object>> expression, string propertyName)
        {
            var memberName = GetMemberName(expression.Body);
            PropertyMap.Add((memberName, propertyName));
        }

        private static string GetMemberName(Expression expression)
        {
            switch (expression.NodeType)
            {
                case ExpressionType.MemberAccess: return ((MemberExpression) expression).Member.Name;
                case ExpressionType.Convert: return GetMemberName(((UnaryExpression) expression).Operand);
                default: throw new NotSupportedException(expression.NodeType.ToString());
            }
        }
    }

    public class PersonMap : Mapping<Person>
    {
        public PersonMap(MappingProvider provider) : base(provider)
        {
            MappingFor(x => x.FirstName, "fn");
            MappingFor(x => x.LastName, "ln");
            MappingFor(x => x.Address, "addr");
        }
    }

    public class AddressMap : Mapping<Address>
    {
        public AddressMap(MappingProvider provider) : base(provider)
        {
            MappingFor(x => x.Street, "st");
            MappingFor(x => x.PostalCode, "pc");
        }
    }

    public class PetMap : Mapping<Pet>
    {
        public PetMap(MappingProvider provider) : base(provider)
        {
            MappingFor(x => x.Breed, "b");
            MappingFor(x => x.Name, "n");
        }
    }
}

PersonFixture.cs

   public sealed class Person
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public Address Address { get; set; }
    }

    public sealed class Address
    {
        public string Street { get; set; }
        public string PostalCode { get; set; }
    }

    public static class PersonFixture
    {
        public static Person JohnSmith = new Person
                                             {
                                                 FirstName = "John",
                                                 LastName = "Smith",
                                                 Address = new Address
                                                               {
                                                                   Street = "123 Elm",
                                                                   PostalCode = "A1A 1A1"
                                                               }
                                             };
    }

PetFixture.cs

    public class PetFixture
    {
        public static Pet Fido = new Pet
                                     {
                                         Breed = "Shitzu",
                                         Name = "Fido"
                                     };
    }
    public class Pet
    {
        public string Breed { get; set; }
        public string Name { get; set; }
    }

VehicleFixture.cs

    public class VehicleFixture
    {
        public static readonly Vehicle ToyotaTundra = new Vehicle
                                                          {
                                                              Make = "Toyota",
                                                              Model = "Tundra"
                                                          };
    }

    public sealed class Vehicle
    {
        [MappingPropertyName("Mk")] public string Make { get; set; }
        [MappingPropertyName("Mdl")] public string Model { get; set; }
    }