using System.Diagnostics;
using System.Text.RegularExpressions;
using InnovEnergy.SysTools.Utils;
using static System.ConsoleColor;

namespace InnovEnergy.SysTools.Process;

using Env = Dictionary<String, String>;


public class SyncProcess
{
    public SysCommand Command      { get; }
    public Env        Environment  { get; }
    public Boolean    LogToConsole { get; }

    public Boolean HasFinished => Process.HasExited;

    private Task<(DateTime timeStamp, StdOutput output)> _ReadStdOut;
    private Task<(DateTime timeStamp, StdError  error )> _ReadStdErr;

    private System.Diagnostics.Process Process { get; }

    public SyncProcess(SysCommand command, Env environment = null, Boolean logToConsole = false)
    {
        Command      = command;
        Environment  = environment;
        LogToConsole = logToConsole;
        Process      = InitProcess();

        _ReadStdOut = ReadNextStdOut();
        _ReadStdErr = ReadNextStdErr();
    }

    private Task<(DateTime timeStamp, StdOutput output)> ReadNextStdOut()
    {
        Debug.Assert(_ReadStdOut == null || _ReadStdOut.IsCompleted);

        return Process
            .StandardOutput
            .ReadLineAsync()
            .ContinueWith(t => (DateTime.Now, SyncProcessOutput.StdOutput(t.Result)));

    }

    private Task<(DateTime timeStamp, StdError error)> ReadNextStdErr()
    {
        Debug.Assert(_ReadStdErr == null || _ReadStdErr.IsCompleted);

        return Process
            .StandardError
            .ReadLineAsync()
            .ContinueWith(t => (DateTime.Now, SyncProcessOutput.StdError(t.Result)));
    }


    private System.Diagnostics.Process InitProcess()
    {
        var startInfo = new ProcessStartInfo
        {
            RedirectStandardOutput = true,
            RedirectStandardError  = true,
            RedirectStandardInput  = true,
            UseShellExecute        = false,
            CreateNoWindow         = true,
            Arguments              = Command.Args.Trim(),
            FileName               = Command.Path,
        };

        foreach (var ev in Environment.EmptyIfNull())
            startInfo.EnvironmentVariables[ev.Key] = ev.Value;

        var proc = new System.Diagnostics.Process
        {
            StartInfo = startInfo,
            EnableRaisingEvents = true
        };

        proc.Start(); // must start BEFORE we access Streams

        return proc;
    }

    public Match ReadStdOutUntil(Regex rx)
    {
        foreach (var l in ReadStdOut())
        {

            var match = rx.Match(l);
            if (match.Success)
                return match;
        }

        throw new Exception("no matching output");
    }

    public String ReadStdOutUntil(String line)
    {
        return ReadStdOutUntil(l => l == line);
    }


    public String ReadStdOutUntil(Func<String, Boolean> predicate)
    {
        foreach (var l in ReadStdOut())
        {
            if (predicate(l))
                return l;
        }

        throw new Exception("no matching output");
    }

    public IEnumerable<String> ReadStdOut(TimeSpan timeOut = default) => ReadMany(timeOut).ThrownOnStdErr();

    public IEnumerable<SyncProcessOutput> ReadMany(TimeSpan timeOut = default)
    {
        SyncProcessOutput output;

        do
        {
            output = ReadNext(timeOut);
            yield return output;
        }
        while (!(output is ExitCode) && !(output is TimeoutError));
    }

    public SyncProcessOutput ReadNext(TimeSpan timeOut = default)
    {
        var wait = timeOut == default
            ? Task.WaitAny(_ReadStdOut, _ReadStdErr)
            : Task.WaitAny(_ReadStdOut, _ReadStdErr, Task.Delay(timeOut));

        if (wait == 2)
        {
            if (LogToConsole)
                "Timeout".WriteLine(Red);

            return SyncProcessOutput.TimeoutError(timeOut);
        }

        if (_ReadStdOut.IsCompleted && _ReadStdErr.IsCompleted)
        {
            var (outTimeStamp, output) = _ReadStdOut.Result;
            var (errTimeStamp, error)  = _ReadStdErr.Result;

            if (outTimeStamp < errTimeStamp && output != null)
            {
                _ReadStdOut = ReadNextStdOut();

                if (LogToConsole)
                    output.Data.WriteLine();

                return output;
            }

            if (error != null)
            {
                _ReadStdErr = ReadNextStdErr();

                if (LogToConsole)
                    error.Data.WriteLine(Red);

                return error;
            }

            Process.WaitForExit();

            var exitCode = Process.ExitCode;

            if (LogToConsole)
            {
                "ExitCode: ".Write(Cyan);
                exitCode.WriteLine(exitCode == 0 ? Green : Red);
            }

            return SyncProcessOutput.ExitCode(exitCode);
        }

        if (_ReadStdOut.IsCompleted)
        {
            var (_, output) = _ReadStdOut.Result;

            if (output != null)
            {
                _ReadStdOut = ReadNextStdOut();
                return output;
            }

        }

        if (_ReadStdErr.IsCompleted)
        {
            var (_, error) = _ReadStdErr.Result;

            if (error != null)
            {
                _ReadStdErr = ReadNextStdErr();
                return error;
            }

        }

        throw new Exception("This should not happen");
    }

    public SyncProcess Terminate()
    {
        Process.Kill();
        return this;
    }

    public SyncProcess Kill()
    {
        Process.Kill();
        return this;
    }

    public void Write(String line)
    {
        Process.StandardInput.WriteLine(line);
    }

    public override String ToString() => Command.ToString();  // TODO: env
}


public abstract class SyncProcessOutput
{
    public static StdOutput    StdOutput    (String    data   ) => new StdOutput(data);
    public static StdError     StdError     (String    data   ) => new StdError(data);
    public static ExitCode     ExitCode     (Int32     data   ) => new ExitCode(data);
    public static TimeoutError TimeoutError (TimeSpan  timeout) => new TimeoutError(timeout);
}

public class ExitCode : SyncProcessOutput
{
    public ExitCode(Int32 data) { Data = data;}
    public Int32 Data { get; }

    public override String ToString() => Data.ToString();
}

public class StdError : SyncProcessOutput
{
    public StdError(String data) { Data = data;}
    public String Data { get; }

    public override String ToString() => Data;
}

public class StdOutput : SyncProcessOutput
{
    public StdOutput(String data) { Data = data; }
    public String Data { get; }

    public override String ToString() => Data;
}

public class TimeoutError : SyncProcessOutput
{
    public TimeoutError(TimeSpan timeout) { Timeout = timeout; }
    public TimeSpan Timeout { get; }

    public override String ToString() => Timeout.ToString();
}


public static class ProcessOutputExtensions
{
    public static IEnumerable<String> ThrownOnStdErr(this IEnumerable<SyncProcessOutput> po)
    {
        foreach (var p in po)
        {
            if (p is StdOutput o)
                yield return o.Data;

            if (p is StdError e)
                throw new Exception(e.Data);

            // Ignore exit code
        }
    }
}