Technical Business Analyst Exercise

Robot.cs

using System;
using System.Collections.Generic;

namespace Robotics
{
    public static class Program
    {
        private static readonly Dictionary<string, Order> Orders = new Dictionary<string, Order>(StringComparer.OrdinalIgnoreCase)
        {
            ["Start"] = Order.Start,
            ["Pause"] = Order.Pause,
            ["Exit"] = Order.Exit,
            ["End"] = Order.End,
            ["Resume"] = Order.Resume
        };

        private static void Main(string[] args)
        {
            Robot process = new Robot();

            PrintIntroduction();
            PrintState(process.CurrentState);

            string line;
            while ((line = Console.ReadLine()) != null)
            {
                Order command;
                if (Orders.TryGetValue(line, out command))
                {
                    process.MoveNext(command);
                    PrintState(process.CurrentState);
                }
                else
                {
                    continue;
                }
            }
        }

        private static void PrintState(RobotState robotState)
        {
            Console.ForegroundColor = ConsoleColor.Blue;
            Console.WriteLine($"Status: I am {robotState}");
            Console.ForegroundColor = ConsoleColor.White;
        }

        private static void PrintIntroduction()
        {
            PrintRobot();

            Console.WriteLine("Beep! I am a Robot!");
            Console.WriteLine();
            Console.WriteLine("You can give me one of the following orders:");

            Console.ForegroundColor = ConsoleColor.Yellow;

            foreach (var order in Orders)
            {
                Console.WriteLine($"* {order.Key}");
            }

            Console.ForegroundColor = ConsoleColor.White;
        }

        private static void PrintRobot()
        {
            string robot = @"
    \.===./   
    | o o |    
     \_O_/     
    /|(\)|\    
   d |___| b   
      |_|      
     (ooo)
            ";
            Console.ForegroundColor = ConsoleColor.Yellow;
            Console.WriteLine(robot);
            Console.ForegroundColor = ConsoleColor.White;
        }
    }

    public enum RobotState
    {
        Inactive,
        Active,
        Paused,
        Terminated
    }

    public enum Order
    {
        Start,
        End,
        Pause,
        Resume,
        Exit
    }

    public class Robot
    {
        private readonly Dictionary<Change, RobotState> _validChanges;
        public RobotState CurrentState { get; private set; }

        public Robot()
        {
            CurrentState = RobotState.Inactive;
            _validChanges = new Dictionary<Change, RobotState>
            {
                [new Change(RobotState.Inactive, Order.Exit)] = RobotState.Terminated,
                [new Change(RobotState.Inactive, Order.Start)] = RobotState.Active,
                [new Change(RobotState.Active, Order.End)] = RobotState.Inactive,
                [new Change(RobotState.Active, Order.Pause)] = RobotState.Paused,
                [new Change(RobotState.Paused, Order.End)] = RobotState.Inactive,
                [new Change(RobotState.Paused, Order.Resume)] = RobotState.Active
            };
        }

        private RobotState GetNext(Order order)
        {
            Change transition = new Change(CurrentState, order);
            RobotState nextState;
            if (_validChanges.TryGetValue(transition, out nextState))
                return nextState;

            PrintError(order);
            return CurrentState;
        }

        private void PrintError(Order order)
        {
            Console.ForegroundColor = ConsoleColor.Red;
            Console.WriteLine($"I can't {order} when I'm {CurrentState}!");
            Console.ForegroundColor = ConsoleColor.White;
        }

        public RobotState MoveNext(Order command)
        {
            CurrentState = GetNext(command);
            return CurrentState;
        }
    }

    class Change
    {
        private readonly RobotState _currentState;
        private readonly Order _command;

        public Change(RobotState currentState, Order command)
        {
            _currentState = currentState;
            _command = command;
        }

        public override int GetHashCode()
        {
            return 17 + 31 * _currentState.GetHashCode() + 31 * _command.GetHashCode();
        }

        public override bool Equals(object obj)
        {
            Change other = obj as Change;
            return other != null && this._currentState == other._currentState && this._command == other._command;
        }
    }
}