WordsPerMinute.cs

using System.Reactive.Linq;

namespace Timed;

public static class WordsPerMinute
{
    private static readonly KeyWatcher keySource = new();
    private static readonly IObservable<IList<char>> wordWindows = keySource.Buffer(
        () => keySource.FirstAsync(char.IsWhiteSpace));

    private static readonly IObservable<string> words = from wordWindow in wordWindows
                                                        select new string(wordWindow.ToArray()).Trim();


    public static void WithGroups()
    {
        IObservable<long> ticks = Observable.Interval(TimeSpan.FromSeconds(6));
        IObservable<int> wordGroupCounts = from tick in ticks
                                           join word in words
                                             on ticks equals words into wordsInTick
                                           from count in wordsInTick.Count()
                                           select count * 10;

        wordGroupCounts.Subscribe(c => Console.WriteLine($"Words per minute: {c}"));

        keySource.Run();
    }

    public static void TimedWindowsWithBuffer()
    {
        IObservable<int> wordGroupCounts =
            from wordGroup in words.Buffer(TimeSpan.FromSeconds(6))
            select wordGroup.Count * 10;
        wordGroupCounts.Subscribe(c => Console.WriteLine("Words per minute: " + c));

        keySource.Run();
    }

    public static void OverlappingTimedWindows()
    {
        IObservable<int> wordGroupCounts =
            from wordGroup in words.Buffer(TimeSpan.FromSeconds(6),
                                           TimeSpan.FromSeconds(1))
            select wordGroup.Count * 10;
        wordGroupCounts.Subscribe(c => Console.WriteLine("Words per minute: " + c));

        keySource.Run();
    }
}