using System.Diagnostics;
using System.IO;
using System.Text;

namespace Zcbot.WindowsNode;

internal sealed class ProcessSupervisor
{
    internal Process Start(
        ProcessStartInfo startInfo,
        string failureMessage = "Adapter worker did not start.") =>
        Process.Start(startInfo)
        ?? throw new InvalidOperationException(failureMessage);

    internal async Task TerminateTreeAsync(
        Process process,
        CancellationToken cancellationToken = default)
    {
        if (process.HasExited) return;
        process.Kill(entireProcessTree: true);
        using var timeout = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
        timeout.CancelAfter(TimeSpan.FromSeconds(30));
        try
        {
            await process.WaitForExitAsync(timeout.Token);
        }
        catch (OperationCanceledException exception) when (!cancellationToken.IsCancellationRequested)
        {
            throw new InvalidOperationException(
                "Adapter worker process tree did not terminate within 30 seconds.", exception);
        }
    }

    internal async Task<string> CaptureOutputAsync(
        StreamReader reader,
        IProgress<string>? progress = null)
    {
        var output = new StringBuilder();
        while (await reader.ReadLineAsync() is { } line)
        {
            if (output.Length < 16 * 1024)
            {
                output.AppendLine(line);
            }
            progress?.Report(line);
        }
        return output.ToString();
    }
}