using System;

using System.Threading.Tasks;

​

​

​

// ####################################################################################

// # Supporting code for DEMO

public class Program

{

    public static async Task Main()

    {

        Console.WriteLine("Starting API request...");

        var amount = (decimal)new Random().Next(1000);

        var response = new TaxController(new Logger()).GetTaxes(new WellsFargoTaxRequest(12345, amount));

        Console.WriteLine($"amount:{amount}, tax:{response.TaxAmount}, bracket:{response.Bracket}");

        Console.WriteLine("API request completed...");

    }

}

// ####################################################################################

// ####################################################################################

​

​

// # DEMO Starts Here...

// # DEMO code is structured as API --> SERVICE LAYER --> THIRD-PARTY PROVIDER LIBRARY

​

// # API Layer

public class TaxController

{

    private readonly ILogger _logger;

​

    public TaxController(ILogger logger)

    {

        _logger = logger;

    }

​

    public TaxServiceResponse GetTaxes(WellsFargoTaxRequest request)

    {

        var taxService = new TaxService(_logger);

        var taxes = taxService.GetTaxes(request);

        return taxes;

    }

}

​

// # Service Layer

public class TaxService

{

    public ILogger _logger;

​

    public TaxService(ILogger logger)

    {

        _logger = logger;

    }

    public TaxServiceResponse GetTaxes(WellsFargoTaxRequest request)

    {

        // Call Third-Party tax provider to get taxes for the product

        var taxProvider = new WellsFargoTaxProvider();

        var taxProviderResponse = taxProvider.GetTaxesAsync(request).Result;

        // Bucket the taxes into different brackets for the response

        bool one = false; // less than 2, bracket 1

        bool two = false; // less than 5, bracket 2

        bool three = false; // less than 10, bracket 3

        bool four = false; // less than 20, bracket 4

        bool five = false; // more than 20, bracket 5

        //19

        if (taxProviderResponse.TaxAmount < 2)

            one = true; //"1"

        if (taxProviderResponse.TaxAmount < 5)

            two = true; //"2"

        if (taxProviderResponse.TaxAmount < 10)

            three = true; //"3"

        if (taxProviderResponse.TaxAmount < 20)

            four = true; //"4"

        if (taxProviderResponse.TaxAmount > 20)

            five = true;

​

        var response = new TaxServiceResponse();

        response.ProductSku = taxProviderResponse.ProductSku;

        response.TaxAmount = taxProviderResponse.TaxAmount;

        response.Bracket  = (one ? "1" : two ? "2" : three ? "3" : four ? "4" : five ? "5" : "error"); //1234

​

        if (response.Bracket == "error")

        {

            _logger.Log("Error!");

        }

        return response;

    }

}

​

public class TaxServiceResponse

{

    public int ProductSku { get; set; }

    public decimal TaxAmount { get; set; }

    public string Bracket { get; set; }

}

​

​

​

​

// ###########################################################################################

// # Third-Party Library (from Wells Fargo) that we don't own, and have to use for integration with

// an external system.

//

// This should be considered a black box and you cannot modify the third-party library.

// 

// The third-party library class does NOT have an interface available for us to use.

// The third-party GetTaxesAsync method is async, there is no non-async version of this method.

//

// #####

// ##### DO NOT MODIFY ANYTHING BELOW THIS SECTION, THIS IS JUST SUPPORTS THE DEMO #####

// #####

public class WellsFargoTaxProvider

{

    public async Task<WellsFargoTaxResponse> GetTaxesAsync(WellsFargoTaxRequest request)

    {

        // outbound call to third-party tax provider

        // inbound response from third-party tax provider

        var response = new WellsFargoTaxResponse(request.ProductSku, request.ProductCost);

        return await Task.FromResult(response);

    }

}

​

public class WellsFargoTaxRequest

{

    public WellsFargoTaxRequest(int sku, decimal cost)

    {

        ProductSku = sku;

        ProductCost = cost;

    }

    public int ProductSku { get; set; }

    public decimal ProductCost { get; set; }

}

​

public class WellsFargoTaxResponse

{

    public WellsFargoTaxResponse(int sku, decimal cost)

    {

        ProductSku = sku;

        TaxAmount = cost * .08m;

    }

    public int ProductSku { get; set; }

    public decimal TaxAmount { get; set; }

}

​

public interface ILogger

{

    public void Log(string message);

}

​

public class Logger : ILogger

{

    public void Log(string message) => Console.WriteLine(message);

}