using System;

using System.Collections.Generic;

using System.Threading;

using System.Threading.Tasks;

using System.Linq;

​

// 1. Implement error/exception handling on the SearchVehicles function on the VehicleBusinessLogic class

// 2. Implement Depedency Injection - Constructor Injection pattern on VehicleBusinessLogic class and decouple VehicleDataAccess implementation

// 3. Inject and utilize LoggingService to log any error(s) as part of error/exception handling added on #1

​

/////////////////////////////////// BEGIN CODE CHANGES ///////////////////////////////////

public class VehicleBusinessLogic

{

    private IVehicleDataAccess _vehicleDataAccess;

    private ILoggingService _loggingService;

    public VehicleBusinessLogic(IVehicleDataAccess vehicleDataAccess, ILoggingService loggingService)

    {

        _vehicleDataAccess = vehicleDataAccess;

        _loggingService = loggingService;

    }

​

    // Retrieves list of vehicles based on criteria

    public async Task<IEnumerable<Vehicle>> SearchVehicles(string make, string year, string model)

    {

        try 

        {

            var vehicles =  await _vehicleDataAccess.GetVehicles(make, year, model);

            if (vehicles.Count() > 0) 

            {

                _loggingService.LogInfo($"Successfully retrieved {vehicles.Count()} vehicles.");

                return vehicles;

            }

            _loggingService.LogInfo($"No vehicles found.");

            return vehicles;        

        }

        catch (Exception ex)

        {

            _loggingService.LogError(ex.Message);

        }

        return Enumerable.Empty<Vehicle>();

    }

}

/////////////////////////////////// END CODE CHANGES ///////////////////////////////////

​

​

public interface IVehicleDataAccess

{

    Task<IEnumerable<Vehicle>> GetVehicles(string make, string year, string model);

}

​

public class VehicleDataAccess : IVehicleDataAccess

{

    public async Task<IEnumerable<Vehicle>> GetVehicles(string make, string year, string model)

    {

        // Assume data retrieved thru repository / db / internal or external service

        return await Task.FromResult<List<Vehicle>>(new List<Vehicle>());

    }

}

​

​

public class LoggingService : ILoggingService

{

     public void LogInfo(string msg)

     {

        Console.WriteLine(msg);

     }

​

     public void LogError(string msg)

     {

        Console.WriteLine(msg);

     }

}

​

public interface ILoggingService

{

    void LogInfo(string msg);

    void LogError(string msg);

}

​

public class Vehicle

{

    public int ID { get; set; }

    public string Make { get; set; }

    public string Year { get; set; }

    public string Model { get; set; }

}