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 ...

         if (!accManager.Authenticate(userId, password))

        {

            Console.WriteLine("Authentication failed. Exiting...");

            return;

        }

        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 ...

        Random random = new Random();

        Parallel.For(0, salesRecords.Count, i =>

        {   

            try{

                salesRecords[i].Qty = random.Next(1, 101); // Random number between 1 and 100

            }

            catch (Exception E)

            {

                return;

            }

        });

        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 ...

        string chosenItemCode = chosenItem;

​

        var selectedRecords = salesRecords

            .Where(record => record.Item == chosenItemCode)

            .OrderByDescending(record => record.Qty)

            .Select(record => new { record.Item, record.Qty });

​

        foreach (var record in selectedRecords)

        {

            Console.WriteLine($"Item Code: {record}, Qty: {record.Qty}");

        }

    }

​

    public static IAccountManager GetAccountManager(string serviceProvider)

    {

        if (serviceProvider == "AWS")

        {

            return new AwsAccountManager(new AwsService());

        }

        else if (serviceProvider == "Azure")

        {

            return new AzureAccountManager(new AzureService());

        }

        else

        {

            throw new ArgumentException("Invalid serviceProvider");

        }

    }

}

​

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 awsService)

    {

        this.awsService = awsService;

    }

​

    public bool Authenticate(string username, string password)

    {

        return awsService.Authenticate(username, password);

    }

}

​

public class AzureAccountManager : IAccountManager

{

    // ...

    private AzureService azureService;

​

    public AzureAccountManager(AzureService azureService)

    {

        this.azureService = azureService;

    }

​

    public bool Authenticate(string username, string password)

    {

        return azureService.AuthUser(username, 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;

    }

}

​