DevServer.cs

using System.Text;
using System.Text.RegularExpressions;
using CliWrap;
using CliWrap.EventStream;

namespace PhotinoSveltekitDevServer;

public class DevServer
{
    private const string URL_PREFIX = "http://";
    private CancellationTokenSource cancelDevServer;
    private Uri devServerUrl;

    public DevServer()
    {
        devServerUrl = null!;
        cancelDevServer = new CancellationTokenSource();
    }

    public async Task Start()
    {
        // start a separate process with the npm command.
        var cmd = Cli.Wrap(ProgramDefaults.DevTerminalExecutable)
            .WithWorkingDirectory(ProgramDefaults.DevUserInterfaceDirectory)
            .WithArguments("/k" + ProgramDefaults.DevRunUserInterfaceDevMode);

        // listen for all incoming events, especially the stdout from the dev server
        await foreach (var cmdEvent in cmd.ListenAsync(Encoding.UTF8, cancelDevServer.Token))
        {
            switch (cmdEvent)
            {
                case StartedCommandEvent started:
                    Console.WriteLine($"Process started; ID: {started.ProcessId}");
                    break;
                case StandardOutputCommandEvent stdOut:
                    Console.WriteLine($"Out> {stdOut.Text}");

                    if (stdOut.Text.Contains(URL_PREFIX))
                    {
                        // if the text contains an url, try to find the url in the message, so that we know
                        // where we should redirect the user, so that he can visit the dev server.
                        devServerUrl = DetermineDevServerUrl(stdOut);
                    }
                    break;
                case StandardErrorCommandEvent stdErr:
                    Console.WriteLine($"Err> {stdErr.Text}");
                    break;
                case ExitedCommandEvent exited:
                    Console.WriteLine($"Process exited; Code: {exited.ExitCode}");
                    break;
            }
        }
    }

    public void WaitUntilReady()
    {
        // wait until the dev server is up and running
        while (true)
        {
            if (IsReady())
            {
                break;
            }

            Thread.Sleep(ProgramDefaults.DevWaitUntilReadyTimeSpan);
        }
    }

    public void Stop()
    {
        cancelDevServer.Cancel();
    }

    public Uri GetUrl()
    {
        return devServerUrl;
    }

    private static Uri DetermineDevServerUrl(StandardOutputCommandEvent stdOut)
    {
        // this is really hacky!
        // since the text contains lots of interesting characters, such as console colorings, arrows etc
        // we need to try to extract the url from all that useless stuff. 
        // This is the best way i came up with after tons of googeling
        var withoutUnicodes = Regex.Replace(stdOut.Text, @"[^\x20-\xaf]+", ""); ;
        var withoutColorCodes = Regex.Replace(withoutUnicodes, "\\[[0-9]{1,2}m", string.Empty);
        withoutColorCodes = withoutColorCodes.Trim();
        var httpIndex = withoutColorCodes.IndexOf(URL_PREFIX);
        var host = withoutColorCodes.Substring(httpIndex);
        return new Uri(host);
    }

    private bool IsReady()
    {
        // assume the dev server is ready, once we were able to determine the dev server url.
        return devServerUrl != null;
    }
}