using MongoDB.Driver;
using MongoDB.Driver.Linq;
using MongoDbGenericRepository.DataAccess.Base;
using MongoDbGenericRepository.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Threading;
using System.Threading.Tasks;

namespace MongoDbGenericRepository.DataAccess.Read
{
    /// <summary>
    /// A class to read MongoDb document.
    /// </summary>
    public partial class MongoDbReader : DataAccessBase
    {
        /// <summary>
        /// The construct of the MongoDbReader class.
        /// </summary>
        /// <param name="mongoDbContext">A <see cref="IMongoDbContext"/> instance.</param>
        public MongoDbReader(IMongoDbContext mongoDbContext) : base(mongoDbContext)
        {
        }

        #region Read TKey

        /// <summary>
        /// Asynchronously returns one document given its id.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="id">The Id of the document you want to get.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<TDocument> GetByIdAsync<TDocument, TKey>(TKey id, string partitionKey = null, CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            var filter = Builders<TDocument>.Filter.Eq("Id", id);
            return await HandlePartitioned<TDocument, TKey>(partitionKey).Find(filter).FirstOrDefaultAsync(cancellationToken);
        }

        /// <summary>
        /// Returns one document given its id.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="id">The Id of the document you want to get.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        public virtual TDocument GetById<TDocument, TKey>(TKey id, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            var filter = Builders<TDocument>.Filter.Eq("Id", id);
            return HandlePartitioned<TDocument, TKey>(partitionKey).Find(filter).FirstOrDefault();
        }

        /// <summary>
        /// Asynchronously returns one document given filter definition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="condition">A mongodb filter definition.</param>
        /// <param name="findOption">A mongodb filter option.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual Task<TDocument> GetOneAsync<TDocument, TKey>(FilterDefinition<TDocument> condition, FindOptions findOption = null,
            string partitionKey = null,
            CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return HandlePartitioned<TDocument, TKey>(partitionKey).Find(condition, findOption).FirstOrDefaultAsync(cancellationToken); 
        }

        /// <summary>
        /// Returns one document given filter definition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="condition">A mongodb filter definition.</param>
        /// <param name="findOption">A mongodb filter option.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        public virtual TDocument GetOne<TDocument, TKey>(FilterDefinition<TDocument> condition, FindOptions findOption = null, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return HandlePartitioned<TDocument, TKey>(partitionKey).Find(condition, findOption).FirstOrDefault(); 
        }

        /// <summary>
        /// Asynchronously returns one document given an expression filter.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<TDocument> GetOneAsync<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, string partitionKey = null, CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return await HandlePartitioned<TDocument, TKey>(partitionKey).Find(filter).FirstOrDefaultAsync(cancellationToken);
        }

        /// <summary>
        /// Returns one document given an expression filter.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        public virtual TDocument GetOne<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return HandlePartitioned<TDocument, TKey>(partitionKey).Find(filter).FirstOrDefault();
        }

        /// <summary>
        /// Returns a collection cursor.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        public virtual IFindFluent<TDocument, TDocument> GetCursor<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return HandlePartitioned<TDocument, TKey>(partitionKey).Find(filter);
        }

        /// <summary>
        /// Returns true if any of the document of the collection matches the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="condition">A mongodb filter definition.</param>
        /// <param name="countOption">A mongodb counting option.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<bool> AnyAsync<TDocument, TKey>(FilterDefinition<TDocument> condition, CountOptions countOption = null, string partitionKey = null,
            CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            var count = await HandlePartitioned<TDocument, TKey>(partitionKey).CountDocumentsAsync(condition, countOption, cancellationToken);
            return count > 0;
        }

        /// <summary>
        /// Returns true if any of the document of the collection matches the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="condition">A mongodb filter definition.</param>
        /// <param name="countOption">A mongodb counting option.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        public virtual bool Any<TDocument, TKey>(FilterDefinition<TDocument> condition, CountOptions countOption = null,
            string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            var count = HandlePartitioned<TDocument, TKey>(partitionKey).CountDocuments(condition, countOption);
            return count > 0;
        }

        /// <summary>
        /// Returns true if any of the document of the collection matches the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<bool> AnyAsync<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, string partitionKey = null, CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            var count = await HandlePartitioned<TDocument, TKey>(partitionKey).CountDocumentsAsync(filter, cancellationToken: cancellationToken);
            return (count > 0);
        }

        /// <summary>
        /// Returns true if any of the document of the collection matches the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        public virtual bool Any<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            var count = HandlePartitioned<TDocument, TKey>(partitionKey).CountDocuments(filter);
            return (count > 0);
        }

        /// <summary>
        /// Asynchronously returns a list of the documents matching the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="condition">A mongodb filter definition.</param>
        /// <param name="findOption">A mongodb filter option.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual Task<List<TDocument>> GetAllAsync<TDocument, TKey>(FilterDefinition<TDocument> condition,
            FindOptions findOption = null, string partitionKey = null, CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return HandlePartitioned<TDocument, TKey>(partitionKey).Find(condition, findOption).ToListAsync(cancellationToken);
        }

        /// <summary>
        /// Returns a list of the documents matching the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="condition">A mongodb filter definition.</param>
        /// <param name="findOption">A mongodb filter option.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        public virtual List<TDocument> GetAll<TDocument, TKey>(FilterDefinition<TDocument> condition, FindOptions findOption = null,
            string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return HandlePartitioned<TDocument, TKey>(partitionKey).Find(condition, findOption).ToList();
        }

        /// <summary>
        /// Asynchronously returns a list of the documents matching the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<List<TDocument>> GetAllAsync<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, string partitionKey = null, CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return await HandlePartitioned<TDocument, TKey>(partitionKey).Find(filter).ToListAsync(cancellationToken);
        }

        /// <summary>
        /// Returns a list of the documents matching the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        public virtual List<TDocument> GetAll<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return HandlePartitioned<TDocument, TKey>(partitionKey).Find(filter).ToList();
        }

        /// <summary>
        /// Asynchronously counts how many documents match the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="condition">A mongodb filter definition.</param>
        /// <param name="countOption">A mongodb counting option.</param>
        /// <param name="partitionKey">An optional partitionKey</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual Task<long> CountAsync<TDocument, TKey>(FilterDefinition<TDocument> condition, CountOptions countOption = null,
            string partitionKey = null, CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return HandlePartitioned<TDocument, TKey>(partitionKey).CountDocumentsAsync(condition, countOption, cancellationToken);
        }

        /// <summary>
        /// Counts how many documents match the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="condition">A mongodb filter definition.</param>
        /// <param name="countOption">A mongodb counting option.</param>
        /// <param name="partitionKey">An optional partitionKey</param>
        public virtual long Count<TDocument, TKey>(FilterDefinition<TDocument> condition, CountOptions countOption = null,
            string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return HandlePartitioned<TDocument, TKey>(partitionKey).CountDocuments(condition, countOption);
        }

        /// <summary>
        /// Asynchronously counts how many documents match the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="partitionKey">An optional partitionKey</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<long> CountAsync<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, string partitionKey = null, CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return await HandlePartitioned<TDocument, TKey>(partitionKey).CountDocumentsAsync(filter, cancellationToken: cancellationToken);
        }

        /// <summary>
        /// Counts how many documents match the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="partitionKey">An optional partitionKey</param>
        public virtual long Count<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return HandlePartitioned<TDocument, TKey>(partitionKey).Find(filter).CountDocuments();
        }

        #endregion

        #region Min / Max

        /// <summary>
        /// Gets the document with the maximum value of a specified property in a MongoDB collections that is satisfying the filter.
        /// </summary>
        /// <typeparam name="TDocument">The document type.</typeparam>
        /// <typeparam name="TKey">The type of the primary key.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="maxValueSelector">A property selector to order by descending.</param>
        /// <param name="partitionKey">An optional partitionKey.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<TDocument> GetByMaxAsync<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, object>> maxValueSelector, string partitionKey = null, CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return await GetCollection<TDocument, TKey>(partitionKey).Find(Builders<TDocument>.Filter.Where(filter))
                                                                     .SortByDescending(maxValueSelector)
                                                                     .Limit(1)
                                                                     .FirstOrDefaultAsync(cancellationToken);
        }

        /// <summary>
        /// Gets the document with the maximum value of a specified property in a MongoDB collections that is satisfying the filter.
        /// </summary>
        /// <typeparam name="TDocument">The document type.</typeparam>
        /// <typeparam name="TKey">The type of the primary key.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="maxValueSelector">A property selector to order by descending.</param>
        /// <param name="partitionKey">An optional partitionKey.</param>
        public virtual TDocument GetByMax<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, object>> maxValueSelector, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return GetCollection<TDocument, TKey>(partitionKey).Find(Builders<TDocument>.Filter.Where(filter))
                                                               .SortByDescending(maxValueSelector)
                                                               .Limit(1)
                                                               .FirstOrDefault();
        }

        /// <summary>
        /// Gets the document with the minimum value of a specified property in a MongoDB collections that is satisfying the filter.
        /// </summary>
        /// <typeparam name="TDocument">The document type.</typeparam>
        /// <typeparam name="TKey">The type of the primary key.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="minValueSelector">A property selector to order by ascending.</param>
        /// <param name="partitionKey">An optional partitionKey.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<TDocument> GetByMinAsync<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, object>> minValueSelector, string partitionKey = null, CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return await GetCollection<TDocument, TKey>(partitionKey).Find(Builders<TDocument>.Filter.Where(filter))
                                                                     .SortBy(minValueSelector)
                                                                     .Limit(1)
                                                                     .FirstOrDefaultAsync(cancellationToken);
        }

        /// <summary>
        /// Gets the document with the minimum value of a specified property in a MongoDB collections that is satisfying the filter.
        /// </summary>
        /// <typeparam name="TDocument">The document type.</typeparam>
        /// <typeparam name="TKey">The type of the primary key.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="minValueSelector">A property selector to order by ascending.</param>
        /// <param name="partitionKey">An optional partitionKey.</param>
        public virtual TDocument GetByMin<TDocument, TKey>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, object>> minValueSelector, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return GetCollection<TDocument, TKey>(partitionKey).Find(Builders<TDocument>.Filter.Where(filter))
                                                               .SortBy(minValueSelector)
                                                               .Limit(1)
                                                               .FirstOrDefault();
        }

        /// <summary>
        /// Gets the maximum value of a property in a mongodb collections that is satisfying the filter.
        /// </summary>
        /// <typeparam name="TDocument">The document type.</typeparam>
        /// <typeparam name="TKey">The type of the primary key.</typeparam>
        /// <typeparam name="TValue">The type of the field for which you want the maximum value.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="maxValueSelector">A property selector to order by ascending.</param>
        /// <param name="partitionKey">An optional partitionKey.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<TValue> GetMaxValueAsync<TDocument, TKey, TValue>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TValue>> maxValueSelector, string partitionKey = null, CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return await GetMaxMongoQuery<TDocument, TKey, TValue>(filter, maxValueSelector, partitionKey)
                                .Project(maxValueSelector)
                                .FirstOrDefaultAsync(cancellationToken);
        }

        /// <summary>
        /// Gets the maximum value of a property in a mongodb collections that is satisfying the filter.
        /// </summary>
        /// <typeparam name="TDocument">The document type.</typeparam>
        /// <typeparam name="TKey">The type of the primary key.</typeparam>
        /// <typeparam name="TValue">The type of the value used to order the query.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="maxValueSelector">A property selector to order by ascending.</param>
        /// <param name="partitionKey">An optional partitionKey.</param>
        public virtual TValue GetMaxValue<TDocument, TKey, TValue>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TValue>> maxValueSelector, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return GetMaxMongoQuery<TDocument, TKey, TValue>(filter, maxValueSelector, partitionKey)
                      .Project(maxValueSelector)
                      .FirstOrDefault();
        }

        /// <summary>
        /// Gets the minimum value of a property in a mongodb collections that is satisfying the filter.
        /// </summary>
        /// <typeparam name="TDocument">The document type.</typeparam>
        /// <typeparam name="TKey">The type of the primary key.</typeparam>
        /// <typeparam name="TValue">The type of the value used to order the query.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="minValueSelector">A property selector to order by ascending.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<TValue> GetMinValueAsync<TDocument, TKey, TValue>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TValue>> minValueSelector, string partitionKey = null, CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return await GetMinMongoQuery<TDocument, TKey, TValue>(filter, minValueSelector, partitionKey).Project(minValueSelector).FirstOrDefaultAsync(cancellationToken);
        }

        /// <summary>
        /// Gets the minimum value of a property in a mongodb collections that is satisfying the filter.
        /// </summary>
        /// <typeparam name="TDocument">The document type.</typeparam>
        /// <typeparam name="TKey">The type of the primary key.</typeparam>
        /// <typeparam name="TValue">The type of the value used to order the query.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="minValueSelector">A property selector to order by ascending.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        public virtual TValue GetMinValue<TDocument, TKey, TValue>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TValue>> minValueSelector, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return GetMinMongoQuery<TDocument, TKey, TValue>(filter, minValueSelector, partitionKey).Project(minValueSelector).FirstOrDefault();
        }


        #endregion Min / Max

        #region Sum TKey

        /// <summary>
        /// Sums the values of a selected field for a given filtered collection of documents.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="selector">The field you want to sum.</param>
        /// <param name="partitionKey">The partition key of your document, if any.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<int> SumByAsync<TDocument, TKey>(Expression<Func<TDocument, bool>> filter,
                                                       Expression<Func<TDocument, int>> selector,
                                                       string partitionKey = null,
                                                       CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return await GetQuery<TDocument, TKey>(filter, partitionKey).SumAsync(selector, cancellationToken);
        }

        /// <summary>
        /// Sums the values of a selected field for a given filtered collection of documents.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="selector">The field you want to sum.</param>
        /// <param name="partitionKey">The partition key of your document, if any.</param>
        public virtual int SumBy<TDocument, TKey>(Expression<Func<TDocument, bool>> filter,
                                                       Expression<Func<TDocument, int>> selector,
                                                       string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return GetQuery<TDocument, TKey>(filter, partitionKey).Sum(selector);
        }

        /// <summary>
        /// Sums the values of a selected field for a given filtered collection of documents.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="selector">The field you want to sum.</param>
        /// <param name="partitionKey">The partition key of your document, if any.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<decimal> SumByAsync<TDocument, TKey>(Expression<Func<TDocument, bool>> filter,
                                                       Expression<Func<TDocument, decimal>> selector,
                                                       string partitionKey = null, CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return await GetQuery<TDocument, TKey>(filter, partitionKey).SumAsync(selector, cancellationToken);
        }

        /// <summary>
        /// Sums the values of a selected field for a given filtered collection of documents.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="selector">The field you want to sum.</param>
        /// <param name="partitionKey">The partition key of your document, if any.</param>
        public virtual decimal SumBy<TDocument, TKey>(Expression<Func<TDocument, bool>> filter,
                                                       Expression<Func<TDocument, decimal>> selector,
                                                       string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return GetQuery<TDocument, TKey>(filter, partitionKey).Sum(selector);
        }

        #endregion Sum TKey
    }

    public partial class MongoDbReader
    {
        /// <summary>
        /// Groups a collection of documents given a grouping criteria, 
        /// and returns a dictionary of listed document groups with keys having the different values of the grouping criteria.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <typeparam name="TGroupKey">The type of the grouping criteria.</typeparam>
        /// <typeparam name="TProjection">The type of the projected group.</typeparam>
        /// <param name="groupingCriteria">The grouping criteria.</param>
        /// <param name="groupProjection">The projected group result.</param>
        /// <param name="partitionKey">The partition key of your document, if any.</param>
        public virtual List<TProjection> GroupBy<TDocument, TGroupKey, TProjection, TKey>(
            Expression<Func<TDocument, TGroupKey>> groupingCriteria,
            Expression<Func<IGrouping<TGroupKey, TDocument>, TProjection>> groupProjection,
            string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
            where TProjection : class, new()
        {
            return HandlePartitioned<TDocument, TKey>(partitionKey)
                             .Aggregate()
                             .Group(groupingCriteria, groupProjection)
                             .ToList();

        }

        /// <summary>
        /// Groups filtered a collection of documents given a grouping criteria, 
        /// and returns a dictionary of listed document groups with keys having the different values of the grouping criteria.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <typeparam name="TGroupKey">The type of the grouping criteria.</typeparam>
        /// <typeparam name="TProjection">The type of the projected group.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="selector">The grouping criteria.</param>
        /// <param name="projection">The projected group result.</param>
        /// <param name="partitionKey">The partition key of your document, if any.</param>
        public virtual List<TProjection> GroupBy<TDocument, TGroupKey, TProjection, TKey>(
            Expression<Func<TDocument, bool>> filter,
            Expression<Func<TDocument, TGroupKey>> selector,
            Expression<Func<IGrouping<TGroupKey, TDocument>, TProjection>> projection,
            string partitionKey = null)
                where TDocument : IDocument<TKey>
                where TKey : IEquatable<TKey>
                where TProjection : class, new()
        {
            var collection = HandlePartitioned<TDocument, TKey>(partitionKey);
            return collection.Aggregate()
                             .Match(Builders<TDocument>.Filter.Where(filter))
                             .Group(selector, projection)
                             .ToList();
        }

        /// <summary>
        /// Groups filtered a collection of documents given a grouping criteria, 
        /// and returns a dictionary of listed document groups with keys having the different values of the grouping criteria.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <typeparam name="TGroupKey">The type of the grouping criteria.</typeparam>
        /// <typeparam name="TProjection">The type of the projected group.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="selector">The grouping criteria.</param>
        /// <param name="projection">The projected group result.</param>
        /// <param name="partitionKey">The partition key of your document, if any.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<List<TProjection>> GroupByAsync<TDocument, TGroupKey, TProjection, TKey>(
            Expression<Func<TDocument, bool>> filter,
            Expression<Func<TDocument, TGroupKey>> selector,
            Expression<Func<IGrouping<TGroupKey, TDocument>, TProjection>> projection,
            string partitionKey = null,
            CancellationToken cancellationToken = default)
                where TDocument : IDocument<TKey>
                where TKey : IEquatable<TKey>
                where TProjection : class, new()
        {
            var collection = HandlePartitioned<TDocument, TKey>(partitionKey);
            return await collection.Aggregate()
                             .Match(Builders<TDocument>.Filter.Where(filter))
                             .Group(selector, projection)
                             .ToListAsync(cancellationToken);
        }

        /// <summary>
        /// Asynchronously returns a paginated list of the documents matching the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="sortSelector">The property selector.</param>
        /// <param name="ascending">Order of the sorting.</param>
        /// <param name="skipNumber">The number of documents you want to skip. Default value is 0.</param>
        /// <param name="takeNumber">The number of documents you want to take. Default value is 50.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<List<TDocument>> GetSortedPaginatedAsync<TDocument, TKey>(
            Expression<Func<TDocument, bool>> filter,
            Expression<Func<TDocument, object>> sortSelector,
            bool ascending = true,
            int skipNumber = 0,
            int takeNumber = 50,
            string partitionKey = null,
            CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            var sorting = ascending
                ? Builders<TDocument>.Sort.Ascending(sortSelector)
                : Builders<TDocument>.Sort.Descending(sortSelector);

            return await HandlePartitioned<TDocument, TKey>(partitionKey)
                                    .Find(filter)
                                    .Sort(sorting)
                                    .Skip(skipNumber)
                                    .Limit(takeNumber)
                                    .ToListAsync(cancellationToken);
        }

        /// <summary>
        /// Asynchronously returns a paginated list of the documents matching the filter condition.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="filter">A LINQ expression filter.</param>
        /// <param name="sortDefinition">The sort definition.</param>
        /// <param name="skipNumber">The number of documents you want to skip. Default value is 0.</param>
        /// <param name="takeNumber">The number of documents you want to take. Default value is 50.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <param name="cancellationToken">An optional cancellation Token.</param>
        public virtual async Task<List<TDocument>> GetSortedPaginatedAsync<TDocument, TKey>(
            Expression<Func<TDocument, bool>> filter,
            SortDefinition<TDocument> sortDefinition,
            int skipNumber = 0,
            int takeNumber = 50,
            string partitionKey = null,
            CancellationToken cancellationToken = default)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return await HandlePartitioned<TDocument, TKey>(partitionKey)
                                    .Find(filter)
                                    .Sort(sortDefinition)
                                    .Skip(skipNumber)
                                    .Limit(takeNumber)
                                    .ToListAsync(cancellationToken);
        }
    }
}