using System;

using System.Collections.Concurrent;

using System.IO;

using System.Threading.Tasks;

​

/*

We have a calculator component. 

The calculator will later be exposed via a web service and called by customers.

We want to track the use of the calculator for analysis purposes, the usage analysis will be used to determine the billing strategy.

A developer in the team wrote the calculator component and the program file as a demonstration.

You need to perform code review.

*/

​

namespace CodeReviewTest

{

    public class Program

    {

        static async Task Main(string[] args)

        {

            ISimpleCalculatorWithCache calculator = new SimpleCalculatorWithCache();

            calculator.Add(1, 2);

            calculator.Subtract(1, 2);

            calculator.Multiply(1, 2);

            calculator.Divide(1, 2);

            var logFile = await calculator.DumpCacheToFile();

            Console.WriteLine(logFile);

            logFile = await calculator.DumpCacheToFile();

            Console.WriteLine(logFile);

            calculator.Divide(2, 0);

            logFile = await calculator.DumpCacheToFile();

            Console.WriteLine(logFile);

        }

    }

​

    public class SimpleCalculatorWithCache : ISimpleCalculatorWithCache

    {

        public ConcurrentQueue<string> _queue { get; set; } = new ConcurrentQueue<string>();

​

        public async Task<string> DumpCacheToFile()

        {

            var allItems = _queue.ToArray();

            _queue.Clear();

​

            var fileName = Path.GetTempFileName();

            File.WriteAllLinesAsync(fileName, allItems);

​

            return fileName;

        }

​

        /// <summary>

        /// Add

        /// </summary>

        public double Add(double a, double b)

        {

            _queue.Enqueue($"Adding {a} and {b}");

            return a + b;

        }

​

        /// <summary>

        /// Subtract

        /// </summary>

        public double Subtract(double a, double b)

        {

            _queue.Enqueue($"Subtracting {a} and {b}");

            return a - b;

        }

​

        /// <summary>

        /// Multiply

        /// </summary>

        public double Multiply(double a, double b)

        {

            _queue.Enqueue($"Multiplying {a} and {b}");

            return a * b;

        }

​

        /// <summary>

        /// Divide

        /// </summary>

        public double Divide(double a, double b)

        {

            _queue.Enqueue($"Dividing {a} by {b}");

            if (b == 0)

            {

                throw new DivideByZeroException("Divisor cannot be zero.");

            }

            return a / b;

        }

    }

​

​

    public interface ISimpleCalculatorWithCache

    {

        /// <summary>

        /// Dump cache to file

        /// </summary>

        Task<string> DumpCacheToFile();

​

        /// <summary>

        /// Add

        /// </summary>

        double Add(double a, double b);

​

        /// <summary>

        /// Subtract

        /// </summary>

        double Subtract(double a, double b);

​

        /// <summary>

        /// Multiply

        /// </summary>

        double Multiply(double a, double b);

​

        /// <summary>

        /// Divide

        /// </summary>

        double Divide(double a, double b);

    }

}

​