using System.Linq.Expressions;
using LinqToDB;
using Nop.Core;

namespace System.Linq;

public static class AsyncIQueryableExtensions
{
    /// <summary>
    /// Determines whether all the elements of a sequence satisfy a condition
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence whose elements to test for a condition</param>
    /// <param name="predicate">A function to test each element for a condition</param>
    /// <returns>
    /// true if every element of the source sequence passes the test in the specified
    /// predicate, or if the sequence is empty; otherwise, false
    /// </returns>
    /// <returns>A task that represents the asynchronous operation</returns>
    public static Task<bool> AllAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, bool>> predicate)
    {
        return AsyncExtensions.AllAsync(source, predicate);
    }

    /// <summary>
    /// Determines whether any element of a sequence satisfies a condition
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence whose elements to test for a condition</param>
    /// <param name="predicate">A function to test each element for a condition</param>
    /// <returns>
    /// true if any elements in the source sequence pass the test in the specified predicate;
    /// otherwise, false
    /// </returns>
    /// <returns>A task that represents the asynchronous operation</returns>
    public static Task<bool> AnyAsync<TSource>(this IQueryable<TSource> source, Expression<Func<TSource, bool>> predicate = null)
    {
        return predicate == null ? AsyncExtensions.AnyAsync(source) : AsyncExtensions.AnyAsync(source, predicate);
    }

    #region Average

    /// <summary>
    /// Computes the average of a sequence that is obtained by
    /// invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values to calculate the average of</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the average of the sequence of values
    /// </returns>
    public static Task<double> AverageAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, int>> predicate)
    {
        return AsyncExtensions.AverageAsync(source, predicate);
    }

    /// <summary>
    /// Computes the average of a sequence that is obtained by
    /// invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values to calculate the average of</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the average of the sequence of values
    /// </returns>
    public static Task<double?> AverageAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, int?>> predicate)
    {
        return AsyncExtensions.AverageAsync(source, predicate);
    }

    /// <summary>
    /// Computes the average of a sequence that is obtained by
    /// invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values to calculate the average of</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the average of the sequence of values
    /// </returns>
    public static Task<double> AverageAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, long>> predicate)
    {
        return AsyncExtensions.AverageAsync(source, predicate);
    }

    /// <summary>
    /// Computes the average of a sequence that is obtained by
    /// invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values to calculate the average of</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the average of the sequence of values
    /// </returns>
    public static Task<double?> AverageAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, long?>> predicate)
    {
        return AsyncExtensions.AverageAsync(source, predicate);
    }

    /// <summary>
    /// Computes the average of a sequence that is obtained by
    /// invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values to calculate the average of</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the average of the sequence of values
    /// </returns>
    public static Task<float> AverageAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, float>> predicate)
    {
        return AsyncExtensions.AverageAsync(source, predicate);
    }

    /// <summary>
    /// Computes the average of a sequence that is obtained by
    /// invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values to calculate the average of</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the average of the sequence of values
    /// </returns>
    public static Task<float?> AverageAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, float?>> predicate)
    {
        return AsyncExtensions.AverageAsync(source, predicate);
    }

    /// <summary>
    /// Computes the average of a sequence that is obtained by
    /// invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values to calculate the average of</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the average of the sequence of values
    /// </returns>
    public static Task<double> AverageAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, double>> predicate)
    {
        return AsyncExtensions.AverageAsync(source, predicate);
    }

    /// <summary>
    /// Computes the average of a sequence that is obtained by
    /// invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values to calculate the average of</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the average of the sequence of values
    /// </returns>
    public static Task<double?> AverageAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, double?>> predicate)
    {
        return AsyncExtensions.AverageAsync(source, predicate);
    }

    /// <summary>
    /// Computes the average of a sequence that is obtained by
    /// invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values to calculate the average of</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the average of the sequence of values
    /// </returns>
    public static Task<decimal> AverageAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, decimal>> predicate)
    {
        return AsyncExtensions.AverageAsync(source, predicate);
    }

    /// <summary>
    /// Computes the average of a sequence that is obtained by
    /// invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values to calculate the average of</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the average of the sequence of values
    /// </returns>
    public static Task<decimal?> AverageAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, decimal?>> predicate)
    {
        return AsyncExtensions.AverageAsync(source, predicate);
    }

    #endregion

    /// <summary>
    /// Determines whether a sequence contains a specified element by using the default
    /// equality comparer
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">An sequence in which to locate item</param>
    /// <param name="item">The object to locate in the sequence</param>
    /// <returns>
    /// true if the input sequence contains an element that has the specified value;
    /// otherwise, false
    /// </returns>
    /// <returns>A task that represents the asynchronous operation</returns>
    public static Task<bool> ContainsAsync<TSource>(this IQueryable<TSource> source, TSource item)
    {
        return AsyncExtensions.ContainsAsync(source, item);
    }

    /// <summary>
    /// Returns the number of elements in the specified sequence that satisfies a condition
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">An sequence that contains the elements to be counted</param>
    /// <param name="predicate">A function to test each element for a condition</param>
    /// <returns>
    /// The number of elements in the sequence that satisfies the condition in the predicate
    /// function
    /// </returns>
    /// <returns>A task that represents the asynchronous operation</returns>
    public static Task<int> CountAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, bool>> predicate = null)
    {
        return predicate == null ? AsyncExtensions.CountAsync(source) : AsyncExtensions.CountAsync(source, predicate);
    }

    /// <summary>
    /// Returns the first element of a sequence that satisfies a specified condition
    /// </summary>
    /// <typeparam name="TSource"></typeparam>
    /// <param name="source">An sequence to return an element from</param>
    /// <param name="predicate">A function to test each element for a condition</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the first element in source that passes the test in predicate
    /// </returns>
    public static Task<TSource> FirstAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, bool>> predicate = null)
    {
        return predicate == null ? AsyncExtensions.FirstAsync(source) : AsyncExtensions.FirstAsync(source, predicate);
    }

    /// <summary>
    /// Returns the first element of a sequence, or a default value if the sequence contains no elements
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">Source</param>
    /// <param name="predicate">Predicate</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the default(TSource) if source is empty; otherwise, the first element in source
    /// </returns>
    public static Task<TSource> FirstOrDefaultAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, bool>> predicate = null)
    {
        return predicate == null ? AsyncExtensions.FirstOrDefaultAsync(source) : AsyncExtensions.FirstOrDefaultAsync(source, predicate);
    }

    /// <summary>
    /// Returns an System.Int64 that represents the number of elements in a sequence
    /// that satisfy a condition
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">An sequence that contains the elements to be counted</param>
    /// <param name="predicate">A function to test each element for a condition</param>
    /// <returns>
    /// The number of elements in source that satisfy the condition in the predicate
    /// function
    /// </returns>
    /// <returns>A task that represents the asynchronous operation</returns>
    public static Task<long> LongCountAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, bool>> predicate = null)
    {
        return predicate == null ? AsyncExtensions.LongCountAsync(source) : AsyncExtensions.LongCountAsync(source, predicate);
    }

    /// <summary>
    /// Returns the maximum value in a generic sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values to determine the maximum of</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the maximum value in the sequence
    /// </returns>
    public static Task<TSource> MaxAsync<TSource>(this IQueryable<TSource> source)
    {
        return AsyncExtensions.MaxAsync(source);
    }

    /// <summary>
    /// Invokes a projection function on each element of a generic sequence
    /// and returns the maximum resulting value
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <typeparam name="TResult">The type of the value returned by the function represented by selector</typeparam>
    /// <param name="source">A sequence of values to determine the maximum of</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the maximum value in the sequence
    /// </returns>
    public static Task<TResult> MaxAsync<TSource, TResult>(this IQueryable<TSource> source,
        Expression<Func<TSource, TResult>> predicate)
    {
        return AsyncExtensions.MaxAsync(source, predicate);
    }

    /// <summary>
    /// Returns the minimum value in a generic sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values to determine the minimum of</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the minimum value in the sequence
    /// </returns>
    public static Task<TSource> MinAsync<TSource>(this IQueryable<TSource> source)
    {
        return AsyncExtensions.MinAsync(source);
    }

    /// <summary>
    /// Invokes a projection function on each element of a generic sequence
    /// and returns the minimum resulting value
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <typeparam name="TResult">The type of the value returned by the function represented by selector</typeparam>
    /// <param name="source">A sequence of values to determine the minimum of</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the minimum value in the sequence
    /// </returns>
    public static Task<TResult> MinAsync<TSource, TResult>(this IQueryable<TSource> source,
        Expression<Func<TSource, TResult>> predicate)
    {
        return AsyncExtensions.MinAsync(source, predicate);
    }

    /// <summary>
    /// Returns the only element of a sequence that satisfies a specified condition,
    /// and throws an exception if more than one such element exists
    /// </summary>
    /// <typeparam name="TSource"></typeparam>
    /// <param name="source">An sequence to return a single element from</param>
    /// <param name="predicate">A function to test an element for a condition</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the single element of the input sequence that satisfies the condition in predicate
    /// </returns>
    public static Task<TSource> SingleAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, bool>> predicate = null)
    {
        return predicate == null ? AsyncExtensions.SingleAsync(source) : AsyncExtensions.SingleAsync(source, predicate);
    }

    /// <summary>
    /// Returns the only element of a sequence that satisfies a specified condition or
    /// a default value if no such element exists; this method throws an exception if
    /// more than one element satisfies the condition
    /// </summary>
    /// <typeparam name="TSource"></typeparam>
    /// <param name="source">A sequence to return a single element from</param>
    /// <param name="predicate">A function to test an element for a condition</param>
    /// <returns>
    /// The single element of the input sequence that satisfies the condition in predicate,
    /// or default(TSource) if no such element is found
    /// </returns>
    /// <returns>A task that represents the asynchronous operation</returns>
    public static Task<TSource> SingleOrDefaultAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, bool>> predicate = null)
    {
        return predicate == null ? AsyncExtensions.SingleOrDefaultAsync(source) : AsyncExtensions.SingleOrDefaultAsync(source, predicate);
    }

    #region Sum

    /// <summary>
    /// Computes the sum of the sequence that is obtained
    /// by invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values of type TSource</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the sum of the projected values
    /// </returns>
    public static Task<decimal> SumAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, decimal>> predicate)
    {
        return AsyncExtensions.SumAsync(source, predicate);
    }

    /// <summary>
    /// Computes the sum of the sequence that is obtained
    /// by invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values of type TSource</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the sum of the projected values
    /// </returns>
    public static Task<decimal?> SumAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, decimal?>> predicate)
    {
        return AsyncExtensions.SumAsync(source, predicate);
    }

    /// <summary>
    /// Computes the sum of the sequence that is obtained
    /// by invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values of type TSource</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the sum of the projected values
    /// </returns>
    public static Task<double?> SumAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, double?>> predicate)
    {
        return AsyncExtensions.SumAsync(source, predicate);
    }

    /// <summary>
    /// Computes the sum of the sequence that is obtained
    /// by invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values of type TSource</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the sum of the projected values
    /// </returns>
    public static Task<float?> SumAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, float?>> predicate)
    {
        return AsyncExtensions.SumAsync(source, predicate);
    }

    /// <summary>
    /// Computes the sum of the sequence that is obtained
    /// by invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values of type TSource</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the sum of the projected values
    /// </returns>
    public static Task<double> SumAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, double>> predicate)
    {
        return AsyncExtensions.SumAsync(source, predicate);
    }

    /// <summary>
    /// Computes the sum of the sequence that is obtained
    /// by invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values of type TSource</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the sum of the projected values
    /// </returns>
    public static Task<int> SumAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, int>> predicate)
    {
        return AsyncExtensions.SumAsync(source, predicate);
    }

    /// <summary>
    /// Computes the sum of the sequence that is obtained
    /// by invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values of type TSource</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the sum of the projected values
    /// </returns>
    public static Task<int?> SumAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, int?>> predicate)
    {
        return AsyncExtensions.SumAsync(source, predicate);
    }

    /// <summary>
    /// Computes the sum of the sequence that is obtained
    /// by invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values of type TSource</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the sum of the projected values
    /// </returns>
    public static Task<long> SumAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, long>> predicate)
    {
        return AsyncExtensions.SumAsync(source, predicate);
    }

    /// <summary>
    /// Computes the sum of the sequence that is obtained
    /// by invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values of type TSource</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the sum of the projected values
    /// </returns>
    public static Task<long?> SumAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, long?>> predicate)
    {
        return AsyncExtensions.SumAsync(source, predicate);
    }

    /// <summary>
    /// Computes the sum of the sequence that is obtained
    /// by invoking a projection function on each element of the input sequence
    /// </summary>
    /// <typeparam name="TSource">The type of the elements of source</typeparam>
    /// <param name="source">A sequence of values of type TSource</param>
    /// <param name="predicate">A projection function to apply to each element</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the sum of the projected values
    /// </returns>
    public static Task<float> SumAsync<TSource>(this IQueryable<TSource> source,
        Expression<Func<TSource, float>> predicate)
    {
        return AsyncExtensions.SumAsync(source, predicate);
    }

    #endregion

    /// <summary>
    /// Asynchronously loads data from query to a dictionary
    /// </summary>
    /// <typeparam name="TSource">Query element type</typeparam>
    /// <typeparam name="TKey">Dictionary key type</typeparam>
    /// <typeparam name="TElement">Dictionary element type</typeparam>
    /// <param name="source">Source query</param>
    /// <param name="keySelector">Source element key selector</param>
    /// <param name="elementSelector">Dictionary element selector</param>
    /// <param name="comparer">Dictionary key comparer</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the dictionary with query results
    /// </returns>
    public static Task<Dictionary<TKey, TElement>> ToDictionaryAsync<TSource, TKey, TElement>(
        this IQueryable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector,
        IEqualityComparer<TKey> comparer = null) where TKey : notnull
    {
        return comparer == null
            ? AsyncExtensions.ToDictionaryAsync(source, keySelector, elementSelector)
            : AsyncExtensions.ToDictionaryAsync(source, keySelector, elementSelector, comparer);
    }

    /// <summary>
    /// Asynchronously loads data from query to a dictionary
    /// </summary>
    /// <typeparam name="TSource">Query element type</typeparam>
    /// <typeparam name="TKey">Dictionary key type</typeparam>
    /// <param name="source">Source query</param>
    /// <param name="keySelector">Source element key selector</param>
    /// <param name="comparer">Dictionary key comparer</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the dictionary with query results
    /// </returns>
    public static Task<Dictionary<TKey, TSource>> ToDictionaryAsync<TSource, TKey>(this IQueryable<TSource> source,
        Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer = null) where TKey : notnull
    {
        return comparer == null
            ? AsyncExtensions.ToDictionaryAsync(source, keySelector)
            : AsyncExtensions.ToDictionaryAsync(source, keySelector, comparer);
    }

    /// <summary>
    /// Asynchronously loads data from query to a list
    /// </summary>
    /// <typeparam name="TSource">Query element type</typeparam>
    /// <param name="source">Source query</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the list with query results
    /// </returns>
    public static Task<List<TSource>> ToListAsync<TSource>(this IQueryable<TSource> source)
    {
        return AsyncExtensions.ToListAsync(source);
    }

    /// <summary>
    /// Asynchronously loads data from query to an array
    /// </summary>
    /// <typeparam name="TSource">Query element type</typeparam>
    /// <param name="source">Source query</param>
    /// <returns>
    /// A task that represents the asynchronous operation
    /// The task result contains the array with query results
    /// </returns>
    public static Task<TSource[]> ToArrayAsync<TSource>(this IQueryable<TSource> source)
    {
        return AsyncExtensions.ToArrayAsync(source);
    }

    /// <summary>
    /// Ctor
    /// </summary>
    /// <param name="source">source</param>
    /// <param name="pageIndex">Page index</param>
    /// <param name="pageSize">Page size</param>
    /// <param name="getOnlyTotalCount">A value in indicating whether you want to load only total number of records. Set to "true" if you don't want to load data from database</param>
    /// <returns>A task that represents the asynchronous operation</returns>
    public static async Task<IPagedList<T>> ToPagedListAsync<T>(this IQueryable<T> source, int pageIndex, int pageSize, bool getOnlyTotalCount = false)
    {
        if (source == null)
            return new PagedList<T>(new List<T>(), pageIndex, pageSize);

        //min allowed page size is 1
        pageSize = Math.Max(pageSize, 1);

        var count = await source.CountAsync();

        var data = new List<T>();

        if (!getOnlyTotalCount)
            data.AddRange(await source.Skip(pageIndex * pageSize).Take(pageSize).ToListAsync());

        return new PagedList<T>(data, pageIndex, pageSize, count);
    }
}