MainWindow.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Threading;

namespace TextAnalyzer
{
    public partial class MainWindow : Window
    {
        private DispatcherTimer? _analysisTimer;
        private bool _isWindowLoaded = false;
        private const string PlaceholderText = "Вставьте или напишите свой текст здесь...";

        public MainWindow()
        {
            InitializeComponent();
            SetupAnalysisTimer();
            this.Loaded += MainWindow_Loaded;
        }

        private void MainWindow_Loaded(object sender, RoutedEventArgs e)
        {
            _isWindowLoaded = true;
            SetPlaceholder();
            AnalyzeText();
        }

        private void SetupAnalysisTimer()
        {
            _analysisTimer = new DispatcherTimer();
            _analysisTimer.Interval = TimeSpan.FromMilliseconds(300);
            _analysisTimer.Tick += (s, e) =>
            {
                if (_analysisTimer != null)
                {
                    _analysisTimer.Stop();
                }
                AnalyzeText();
            };
        }

        private void InputTextBox_TextChanged(object sender, TextChangedEventArgs e)
        {
            if (!_isWindowLoaded || _analysisTimer == null)
            {
                return;
            }
            _analysisTimer.Stop();
            _analysisTimer.Start();
        }

        private void AnalyzeText()
        {
            string text = InputTextBox.Text;
            if (text == PlaceholderText)
            {
                text = "";
            }

            int wordCount = Regex.Matches(text, @"[\p{L}\p{N}']+").Count;
            WordsCountLabel.Text = wordCount.ToString("N0");

            CharsCountLabel.Text = text.Length.ToString("N0");

            int sentenceCount = Regex.Matches(text, @"[.!?]+").Count;
            SentencesCountLabel.Text = sentenceCount.ToString("N0");

            int paragraphCount = text.Split(new[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries).Length;
            ParagraphsCountLabel.Text = paragraphCount.ToString("N0");

            const int wordsPerMinute = 200;
            double minutesToRead = (double)wordCount / wordsPerMinute;
            TimeSpan timeToRead = TimeSpan.FromMinutes(minutesToRead);
            if (timeToRead.TotalSeconds < 60)
            {
                ReadingTimeLabel.Text = $"~ {timeToRead.Seconds} сек";
            }
            else
            {
                ReadingTimeLabel.Text = $"~ {timeToRead.Minutes} мин {timeToRead.Seconds} сек";
            }

            if (string.IsNullOrWhiteSpace(text))
            {
                FrequencyListView.ItemsSource = null;
                return;
            }

            var wordFrequencies = Regex.Matches(text, @"[\p{L}\p{N}']+")
                .Cast<Match>()
                .Select(m => m.Value.ToLowerInvariant())
                .GroupBy(w => w)
                .ToDictionary(g => g.Key, g => g.Count())
                .OrderByDescending(kvp => kvp.Value)
                .Take(10);

            FrequencyListView.ItemsSource = wordFrequencies;
        }

        private void SetPlaceholder()
        {
            InputTextBox.Text = PlaceholderText;
            InputTextBox.Foreground = new SolidColorBrush(Color.FromRgb(119, 119, 119));
        }

        private void RemovePlaceholder()
        {
            InputTextBox.Text = "";
            InputTextBox.Foreground = new SolidColorBrush(Colors.White);
        }

        private void InputTextBox_GotFocus(object sender, RoutedEventArgs e)
        {
            if (InputTextBox.Text == PlaceholderText)
            {
                RemovePlaceholder();
            }
        }

        private void InputTextBox_LostFocus(object sender, RoutedEventArgs e)
        {
            if (string.IsNullOrWhiteSpace(InputTextBox.Text))
            {
                SetPlaceholder();
            }
        }
    }
}