﻿using System;
using System.Collections.Generic;
using System.Data.Entity.Infrastructure;
using System.Linq;
using System.Linq.Expressions;
using System.Threading;
using System.Threading.Tasks;
using System.Web;
/**
 * Async query provider
 * For testing. It looks like these classes can be reused
 **/


namespace MOQEF
{
    public class TestDbAsyncQueryProvider<TEntity> : IDbAsyncQueryProvider
    {
        private readonly IQueryProvider  _inner;
        internal TestDbAsyncQueryProvider(IQueryProvider inner){
            _inner = inner;
        }

        public IQueryable CreateQuery(Expression expression){
            return new TestDbAsyncEnumerable<TEntity>(expression);
        }

        public IQueryable<TElement> CreateQuery<TElement>(Expression expression){
            return new TestDbAsyncEnumerable<TElement>(expression);
        }

        public object Execute(Expression expression){
            return _inner.Execute(expression);
        }

        public TResult Execute<TResult>(Expression expression)
        {
            return _inner.Execute<TResult>(expression);
        }

        public Task<object> ExecuteAsync(Expression expression, CancellationToken cancellationToken){
            return Task.FromResult(Execute(expression));
        }

        public Task<TResult> ExecuteAsync<TResult>(Expression expression, CancellationToken cancellationToken){
            return Task.FromResult(Execute<TResult>(expression));
        }


           
    }
    internal class TestDbAsyncEnumerable<T> : EnumerableQuery<T>, IDbAsyncEnumerable<T>, IQueryable<T>
    {
        public TestDbAsyncEnumerable(IEnumerable<T> enumerable)
            : base(enumerable)
        { }

        public TestDbAsyncEnumerable(Expression expression)
            : base(expression)
        { }

        public IDbAsyncEnumerator<T> GetAsyncEnumerator()
        {
            return new TestDbAsyncEnumerator<T>(this.AsEnumerable().GetEnumerator());
        }

        IDbAsyncEnumerator IDbAsyncEnumerable.GetAsyncEnumerator()
        {
            return GetAsyncEnumerator();
        }

        IQueryProvider IQueryable.Provider
        {
            get { return new TestDbAsyncQueryProvider<T>(this); }
        }
    }

    internal class TestDbAsyncEnumerator<T> : IDbAsyncEnumerator<T>
    {
        private readonly IEnumerator<T> _inner;

        public TestDbAsyncEnumerator(IEnumerator<T> inner)
        {
            _inner = inner;
        }

        public void Dispose()
        {
            _inner.Dispose();
        }

        public Task<bool> MoveNextAsync(CancellationToken cancellationToken)
        {
            return Task.FromResult(_inner.MoveNext());
        }

        public T Current
        {
            get { return _inner.Current; }
        }

        object IDbAsyncEnumerator.Current
        {
            get { return Current; }
        } 
    }
}