using System;

using System.Collections.Generic;

using System.Linq;

using System.Threading.Tasks;

​

public class Program

{

    private static List<SalesRecord> salesRecords = new();

    public static void Main()

    {

        var currentServiceProvider = "AWS";

        var accManager = GetAccountManager(currentServiceProvider);

        Console.WriteLine("Enter User ID:");

        var userId = Console.ReadLine();

        Console.WriteLine("Enter Password:");

        var password = Console.ReadLine();

        // ... Authenticate user ...

        var isAuthenticated = accManager.Authenticate(userId, password);

        if (!isAuthenticated) {

            Console.WriteLine("Invalid UserID or Password!");

            Console.WriteLine("Enter User ID:");

            userId = Console.ReadLine();

            Console.WriteLine("Enter Password:");

            password = Console.ReadLine();

            isAuthenticated = accManager.Authenticate(userId, password);

        }

        for (var i = 0; i < 10000; i++)

        {

            var item = i < 4000 ? "A" : i < 8000 ? "B" : "C";

            salesRecords.Add(new SalesRecord(item));

        }

        // ... Propagate salesRecords with random quantities ...

        Parallel.ForEach(salesRecords, record =>

        {

            record.Qty = 5;

        });

        foreach (SalesRecord record in salesRecords) {

            AssignRandomQuantity(record);

        }

        Console.WriteLine("Which item do you want to view? (A/B/C):");

        var chosenItem = Console.ReadLine();

        // ... Display items by filtering and sorting them in descending order with linq expression ...

        var itemSales = salesRecords

            .Where(sr => sr.Item.Equals(chosenItem))

            .OrderByDescending(sr => sr.Qty);

​

        foreach (var sale in itemSales)

        {

            Console.WriteLine($"Item {sale.Item}: Qty {sale.Qty}");

        }

    }

    private static void AssignRandomQuantity(SalesRecord record)

    {

        record.Qty = 5;

    }

​

    public static IAccountManager GetAccountManager(string serviceProvider)

    {

        switch (serviceProvider.ToLower())

        {

            case "aws":

                return new AwsAccountManager();

            case "azure":

                return new AzureAccountManager();

            default:

                throw new ArgumentException("Invalid service provider");

        }

    }

}

​

public struct SalesRecord

{

    public string Item { get; set; }

​

    public int Qty { get; set; }

​

    public SalesRecord(string item)

    {

        Item = item;

        Qty = 0;

    }

}

​

public interface IAccountManager

{

    public bool Authenticate(string userId, string password);

}

​

// ... Implement the IAccountManager interface ...

public class AwsAccountManager : IAccountManager

{

    private AwsService awsService;

​

    public AwsAccountManager()

    {

        awsService = new AwsService();

    }

​

    public bool Authenticate(string userId, string password)

    {

        return awsService.Authenticate(userId, password);

    }

}

​

public class AzureAccountManager : IAccountManager

{

    private AzureService azureService;

​

    public AzureAccountManager()

    {

        azureService = new AzureService();

    }

​

    public bool Authenticate(string userId, string password)

    {

        return azureService.AuthUser(userId, password);

    }

}

​

// Do not modify below classes.

public class AwsService

{

    public bool Authenticate(string userId, string password)

    {

        return userId == "aws" && password == "abc123";

    }

​

    public bool DeleteUser(string userId)

    {

        return true;

    }

}

​

public class AzureService

{

    public bool AuthUser(string userId, string password)

    {

        return userId == "azure" && password == "abc321";

    }

​

    public bool RemoveUser(string userId)

    {

        return true;

    }

}

​