ReEdit/TerminalTextEdit.cs

using Godot;
using System;
using Godot.Collections;

[Tool]
public partial class TerminalTextEdit : TextEdit
{
    private Dictionary _psProcess = new Dictionary();
    private FileAccess _psOutputPipe;
    private FileAccess _psInputPipe;

    // Track historical boundaries so users can't delete past output
    private int _protectedLine = 0;
    private int _protectedColumn = 0;
    private bool _isUpdatingText = false;

    public override void _Ready()
    {
        // Initial setup
        Text = "ReEdit Terminal - 0.1.3\nWindows PowerShell\nCopyright (C) Microsoft Corporation. All rights reserved.\n\nTry the new cross-platform PowerShell https://aka.ms/pscore6\n\n";
        _protectedLine = GetLineCount() - 1;
        _protectedColumn = GetLine(_protectedLine).Length;

        // Force caret to the active prompt area
        SetCaretLine(_protectedLine);
        SetCaretColumn(_protectedColumn);

        TextChanged += OnTextChanged;
        StartPowerShell();
    }

    private void StartPowerShell()
    {
        var args = new string[] {
            "-NoExit",
            "-NoProfile",
            "-Command",
            "$OutputEncoding = [System.Text.Encoding]::UTF8"
        };

        _psProcess = OS.ExecuteWithPipe("powershell.exe", args);

        if (_psProcess.Count == 0)
        {
            AppendSystemText("\n[Error: Failed to initialize PowerShell process.]\n");
            return;
        }

        _psOutputPipe = (FileAccess)_psProcess["stdio"];
        _psInputPipe = (FileAccess)_psProcess["stdio"];
    }

    public override void _GuiInput(InputEvent @event)
    {
        if (@event is InputEventKey keyEvent && keyEvent.Pressed)
        {
            if (keyEvent.Keycode == Key.Backspace)
            {
                if (GetCaretLine() < _protectedLine ||
                   (GetCaretLine() == _protectedLine && GetCaretColumn() <= _protectedColumn))
                {
                    AcceptEvent(); // Kill the input event before it acts
                    return;
                }
            }

            if (keyEvent.Keycode == Key.Enter || keyEvent.Keycode == Key.KpEnter)
            {
                string activeLine = GetLine(GetCaretLine());
                string command = activeLine.Substring(_protectedColumn).Trim();

                if (!string.IsNullOrWhiteSpace(command) && _psInputPipe != null)
                {
                    _psInputPipe.StoreLine(command);
                }

                _isUpdatingText = true;
                InsertTextAtCaret("\n");
                _protectedLine = GetLineCount() - 1;
                _protectedColumn = 0;
                _isUpdatingText = false;

                AcceptEvent();
            }
        }
    }

    private void OnTextChanged()
    {
        if (_isUpdatingText) return;

        if (GetCaretLine() < _protectedLine ||
           (GetCaretLine() == _protectedLine && GetCaretColumn() < _protectedColumn))
        {
            _isUpdatingText = true;
            SetCaretLine(_protectedLine);
            SetCaretColumn(GetLine(_protectedLine).Length);
            _isUpdatingText = false;
        }
    }

    public override void _Process(double delta)
    {
        if (_psOutputPipe != null && _psOutputPipe.GetLength() > 0)
        {
            string newText = _psOutputPipe.GetAsText();
            if (!string.IsNullOrEmpty(newText))
            {
                AppendSystemText(newText);
            }
        }
    }

    private void AppendSystemText(string incoming)
    {
        _isUpdatingText = true;

        int oldCaretLine = GetCaretLine();
        int oldCaretCol = GetCaretColumn();
        SetCaretLine(GetLineCount() - 1);
        SetCaretColumn(GetLine(GetLineCount() - 1).Length);
        InsertTextAtCaret(incoming);
        _protectedLine = GetLineCount() - 1;
        _protectedColumn = GetLine(_protectedLine).Length;
        SetCaretLine(_protectedLine);
        SetCaretColumn(_protectedColumn);

        _isUpdatingText = false;
    }

    public override void _ExitTree()
    {
        if (_psProcess.Count > 0 && _psProcess.ContainsKey("pid"))
        {
            int pid = (int)_psProcess["pid"];
            OS.Kill(pid);
        }
    }
}