using System.Diagnostics;
using System.Globalization;
using System.Text;
using System.Text.RegularExpressions;
using System.IO;

namespace AmigaDB.VideoRenderer.Services;

public sealed partial class ProcessRunner
{
    public async Task<string> RunAsync(
        string executable,
        IEnumerable<string> arguments,
        Action<string>? log,
        Action<TimeSpan>? position,
        CancellationToken token,
        bool allowFailure = false)
    {
        ProcessStartInfo start = new()
        {
            FileName = executable,
            UseShellExecute = false,
            CreateNoWindow = true,
            RedirectStandardError = true,
            RedirectStandardOutput = true,
            StandardErrorEncoding = Encoding.UTF8,
            StandardOutputEncoding = Encoding.UTF8
        };
        foreach (string argument in arguments)
            start.ArgumentList.Add(argument);

        using Process process = new() { StartInfo = start, EnableRaisingEvents = true };
        StringBuilder output = new();
        process.Start();

        Task stdout = PumpAsync(process.StandardOutput, output, log, position, token);
        Task stderr = PumpAsync(process.StandardError, output, log, position, token);
        using CancellationTokenRegistration registration = token.Register(() =>
        {
            try { if (!process.HasExited) process.Kill(true); } catch { }
        });

        await Task.WhenAll(stdout, stderr, process.WaitForExitAsync(token));
        if (process.ExitCode != 0 && !allowFailure)
            throw new InvalidOperationException($"Process exited with code {process.ExitCode}.\n{output}");
        return output.ToString();
    }

    private static async Task PumpAsync(
        StreamReader reader, StringBuilder output, Action<string>? log,
        Action<TimeSpan>? position, CancellationToken token)
    {
        while (await reader.ReadLineAsync(token) is { } line)
        {
            output.AppendLine(line);
            log?.Invoke(line);
            Match match = TimeRegex().Match(line);
            if (match.Success && TimeSpan.TryParse(match.Groups[1].Value, CultureInfo.InvariantCulture, out TimeSpan time))
                position?.Invoke(time);
        }
    }

    [GeneratedRegex(@"time=(\d{2}:\d{2}:\d{2}(?:\.\d+)?)", RegexOptions.CultureInvariant)]
    private static partial Regex TimeRegex();
}