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

namespace MongoPipeline
{
    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 matchFilter = Builders<Sample>.Filter.Where(item => item.EntryName == "Common");
            var projectionFilter = Builders<Sample>.Projection.Expression((item) => item.ReferenceComponents.Where(component => component.Name == "Animal"));

            var pipeline = collection
                .Aggregate()
                .Match(matchFilter)
                .Project(projectionFilter);

            var result = pipeline.ToList();

            Console.Write(result);
        }
    }

    public class Sample
    {
        [BsonId]
        public ObjectId EntryId { get; set; }
        
        [BsonElement("name")]
        public string EntryName { get; set; }

        [BsonElement("ref")]
        public List<ReferenceComponents> ReferenceComponents { get; set; }
    }

    public class ReferenceComponents
    {
        [BsonElement("comp_name")]
        public string Name { get; set; }

        [BsonElement("comp_ref")]
        public string Ref { get; set; }
    }
}