using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Threading;
using System.Threading.Tasks;
using MongoDB.Driver;
using MongoDB.Driver.Linq;
using xModels.Base;

namespace xDataService.Mongo {
    public class XMongoQueryable<TEntity, TKey> : IMongoQueryable<TEntity>
        where TEntity : XBaseEntity<TKey> {
            private readonly IMongoCollection<TEntity> collection;

            public Type ElementType { get; }
            public IQueryable<TEntity> Items { get; }
            public Expression Expression { get; }
            public IQueryProvider Provider { get; }

            public XMongoQueryable (
                IQueryable<TEntity> items,
                IMongoCollection<TEntity> collection
            ) {
                //
                this.Items = items;
                this.collection = collection;

                //
                Provider = items.Provider;
                Expression = items.Expression;
                ElementType = items.ElementType;
            }

            public IEnumerator<TEntity> GetEnumerator () {
                return Items.GetEnumerator ();
            }

            public QueryableExecutionModel GetExecutionModel () {
                return collection.AsQueryable ().GetExecutionModel ();
            }

            public IAsyncCursor<TEntity> ToCursor (CancellationToken cancellationToken = default) {
                return new XMongoAsyncCursor<TEntity> (Items);
            }

            public Task<IAsyncCursor<TEntity>> ToCursorAsync (CancellationToken cancellationToken = default) {
                return Task.Run (() => new XMongoAsyncCursor<TEntity> (Items) as IAsyncCursor<TEntity>);
            }

            IEnumerator IEnumerable.GetEnumerator () {
                return Items.GetEnumerator ();
            }
        }
}