inabox/InABox.Core/LinkedProperty.cs

using System;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using FluentResults;

namespace InABox.Core
{
    public interface ILinkedProperty
    {
        Type Type { get; }
        String Path { get; }
        String Source { get; }
        String Target { get; }
        void Update(object? from, object? to);

        /// <summary>
        /// This equality comparer checks against type, path, source and target
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        bool Equals(object obj);
    }

    public class LinkedProperty<TLinkedEntity, TEntityLink, TType> : ILinkedProperty
        where TLinkedEntity : class
        where TEntityLink : class
    {
        public Type Type => typeof(TLinkedEntity);
        public String Path { get; }

        private Func<TEntityLink?, TType> _source;
        public String Source { get; }
        public String Target { get; }

        private readonly Func<TLinkedEntity?, TType, Result<TType>>? _func;
        
        public override string ToString()
        {
            return $"{Type.EntityName().Split('.').Last()}: {Path}{(String.IsNullOrWhiteSpace(Path) ? "" : ".")}{Source} => {Target}";
        }
        
        public LinkedProperty(Expression<Func<TLinkedEntity, TEntityLink>> path, 
            Expression<Func<TEntityLink?, TType>> source,
            Expression<Func<TLinkedEntity?, TType>> target,
            Func<TLinkedEntity?,TType, Result<TType>>? func = null)
        {
            Path = CoreUtils.GetFullPropertyName(path, ".");
            Source = CoreUtils.GetFullPropertyName(source, ".");
            Target = CoreUtils.GetFullPropertyName(target,".");
            _func = func;
            _source = source.Compile();
        }

        public void Update(object? from, object? to)
        {
            if (from != null && to != null)
            {
                var value = _source.Invoke(from as TEntityLink);
                //var value = CoreUtils.GetPropertyValue(from, Source);
                if (_func != null)
                {
                    var result = _func(to as TLinkedEntity, value);
                    if (!result.IsSuccess)
                        return;
                    value = result.Value;
                }
                CoreUtils.SetPropertyValue(to, Target, value);
            }
        }

        public override bool Equals(object obj)
        {
            if (obj is ILinkedProperty src)
            {
                return 
                    (obj as ILinkedProperty).Type == Type &&
                        String.Equals(src.Path,Path)
                       && String.Equals(src.Source, Source)
                       && String.Equals(src.Target, Target);
            }
            return false;
        }


    }
}