using MongoDB.Bson.Serialization;
using MongoDB.Driver;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Linq.Expressions;

namespace MongoSample
{
    class Program
    {
        static void Main(string[] args)
        {
            var client = new MongoClient("mongodb://localhost:27017/");
            var db = client.GetDatabase("testing");
            var collection = db.GetCollection<Sample>("entries");

            var first = new Sample()
            {
                EntryName = "Common",
                ReferenceComponents = new List<ReferenceComponents>()
                {
                    new ReferenceComponents() { Name = "Animal", Ref = "Cat/1234" },
                    new ReferenceComponents() { Name = "Animal", Ref = "Dog/1234"},
                    new ReferenceComponents() { Name = "Plant", Ref = "Tomato/1234"}
                }
            };

            var second = new Sample()
            {
                EntryName = "Common",
                ReferenceComponents = new List<ReferenceComponents>()
                {
                    new ReferenceComponents() { Name = "Animal", Ref = "Elephant/1234" },
                    new ReferenceComponents() { Name = "Animal", Ref = "Jaguar/1234"},
                    new ReferenceComponents() { Name = "Innanimate", Ref = "Rock/1234"}
                }
            };

            collection.InsertOne(first);
            collection.InsertOne(second);

            var filter = Builders<Sample>.Filter.Where(item => item.EntryName == "Common");
            Expression<Func<Sample, IEnumerable<ReferenceComponents>>> projection = (entry) =>
                    entry
                        .ReferenceComponents
                        .Where(item => item.Name == "Animal");

            var aggregationPipelin = collection
                .Aggregate()
                .Match(filter)
                .Project(projection);

            var result = aggregationPipelin.ToCursorAsync().GetAwaiter().GetResult();

            // Here I am expecting the Reference components with the name Animal 
            // but insted I get an exception :(
        }
    }

    public class Sample
    {
        
        public string EntryName { get; set; }
        public List<ReferenceComponents> ReferenceComponents { get; set; }
    }

    public class ReferenceComponents
    {
        public string Name { get; set; }
        public string Ref { get; set;  }
    }
}