ExplanatoryDictionary

using System;
using System.Collections.Generic;
using System.Text;

class Program
{
    private const string ExitCommandEng = "exit";
    private const string ExitCommandRus = "выход";

    private const string WarningMessageEmptyInput = "Пустой ввод. Попробуйте снова.";
    private const string ErrorMessageWordNotFound = "Слово \"{0}\" не найдено в словаре.";
    private const string Title = "ENG ⇄ RUS Dictionary";
    private const string InfoMessageProgramEnded = "Программа завершена.";
    private const string StartMessage = "Введите слово(или 'exit'/'выход' для выхода): ";
    private const string BoarderLine = "======================================";
    private const string HeaderTitle = "        ENG ⇄ RUS Dictionary          ";

    public static void Main()
    {
        Console.Clear();
        Console.OutputEncoding = Encoding.UTF8;
        Console.Title = Title;

        var dictionary = new Dictionary<string, string>
        {
            { "apple", "яблоко" },
            { "book", "книга" },
            { "car", "машина" },
            { "house", "дом" },
            { "computer", "компьютер" }
        };

        PrintHeader();

        bool isRunning = true;

        while (isRunning == true)
        {
            Console.Write(StartMessage);

            string? input = Console.ReadLine();

            if (string.IsNullOrWhiteSpace(input))
            {
                PrintWarning(WarningMessageEmptyInput);

                continue;
            }

            string trimmedInput = input.Trim();
            string normalizedInput = trimmedInput.ToLower();

            if (normalizedInput == ExitCommandEng ||
                normalizedInput == ExitCommandRus)
            {
                isRunning = false;
                PrintInfo(InfoMessageProgramEnded);
                continue;
            }

            if (dictionary.TryGetValue(normalizedInput, out string russianTranslation))
            {
                PrintSuccess($"{trimmedInput} → {russianTranslation}");
                continue;
            }

            bool isFound = false;

            foreach (KeyValuePair<string, string> pair in dictionary)
            {
                if (string.Equals(pair.Value, trimmedInput, StringComparison.OrdinalIgnoreCase))
                {
                    PrintSuccess($"{trimmedInput} → {pair.Key}");
                    isFound = true;

                    break;
                }
            }

            if (isFound == false)
            {
                PrintError(string.Format(ErrorMessageWordNotFound, trimmedInput));
            }
        }
    }

    private static void PrintHeader()
    {
        Console.ForegroundColor = ConsoleColor.Cyan;
        Console.WriteLine(BoarderLine);
        Console.WriteLine(HeaderTitle);
        Console.WriteLine(BoarderLine);
        Console.ResetColor();
        Console.WriteLine();
    }

    private static void PrintSuccess(string message)
    {
        Console.ForegroundColor = ConsoleColor.Green;
        Console.WriteLine($"✔ {message}");
        Console.ResetColor();
        Console.WriteLine();
    }

    private static void PrintWarning(string message)
    {
        Console.ForegroundColor = ConsoleColor.Yellow;
        Console.WriteLine($"! {message}");
        Console.ResetColor();
        Console.WriteLine();
    }

    private static void PrintError(string message)
    {
        Console.ForegroundColor = ConsoleColor.Red;
        Console.WriteLine($"✘ {message}");
        Console.ResetColor();
        Console.WriteLine();
    }

    private static void PrintInfo(string message)
    {
        Console.ForegroundColor = ConsoleColor.Cyan;
        Console.WriteLine(message);
        Console.ResetColor();
        Console.WriteLine();
    }
}