ansi-fahrplan/UiElements/InputBox.cs

using System.Runtime.InteropServices.Marshalling;
using Mindmagma.Curses;

namespace ANSI_Fahrplan.UiElements;

public class InputBox {
	public delegate void InputCompleted (string input);

	public void RequestInput (nint screen, InputHandler inputHandler, InputCompleted callback, string question) {
		const int boxPaddingTop    = 1;
		const int boxPaddingSides  = 2;
		const int boxPaddingBottom = 2;

		const int boxMarginTopBottom = 1;
		const int boxMarginSides     = 2;
		
		NCurses.GetMaxYX (screen, out int height, out int width);

		// Contents inside the question box may not be larger than these
		int maxInnerWidth  = width  - (boxPaddingSides * 2) - (boxMarginSides * 2);
		int maxInnerHeight = height - boxPaddingTop - boxPaddingBottom - boxMarginTopBottom;

		using var strReader = new StringReader (question);
		string? inStr;
		int innerWidth  = 1;
		int innerHeight = 1;
		while ((inStr = strReader.ReadLine ()) is not null) {
			if (inStr.Length > innerWidth) innerWidth = inStr.Length;

			if (innerWidth > maxInnerWidth) {
				innerWidth = maxInnerWidth;
				innerHeight += (int) Math.Ceiling (inStr.Length / (double) maxInnerWidth);
			} else {
				innerHeight ++;
			}
		}

		int boxWidth   = innerWidth   + (boxPaddingSides * 2);
		int boxHeight  = innerHeight  + boxPaddingTop + boxPaddingBottom;
		int boxAnchorX = (width  / 2) - (boxWidth  / 2);
		int boxAnchorY = (height / 2) - (boxHeight / 2);

		var boxWin = NCurses.SubWindow (screen, boxHeight, boxWidth, boxAnchorY, boxAnchorX);
		NCurses.Box (boxWin, (char) 0, (char) 0);

		NCurses.Refresh ();
		NCurses.WindowRefresh (boxWin);

		int questionTextWinAnchorX = boxAnchorX + boxPaddingSides;
		int questionTextWinAnchorY = boxAnchorY + boxPaddingTop;

		var questionTextWin = NCurses.SubWindow (boxWin, innerHeight, innerWidth, questionTextWinAnchorY, questionTextWinAnchorX);
		NCurses.WindowAddString (questionTextWin, question.Trim ());

		NCurses.WindowRefresh (questionTextWin);

		int inputFieldWinX = questionTextWinAnchorX;
		int inputFieldWinY = boxAnchorY + boxHeight - boxMarginTopBottom - 1;

		var inputFieldWin = NCurses.SubWindow (boxWin, 1, innerWidth, inputFieldWinY, inputFieldWinX);
		NCurses.WindowBackground (inputFieldWin, ColorSchemes.TextInputField ());
		NCurses.WindowAttributeSet (inputFieldWin, ColorSchemes.TextInputField ());

		NCurses.WindowRefresh (inputFieldWin);

		NCurses.MoveWindow (inputFieldWin, inputFieldWinY, inputFieldWinX);
		NCurses.SetCursor (1);
		NCurses.Echo ();

		var userInput = "";
		InputHandler.KeypressEventHandler handlerFunction = (object sender, NCursesKeyPressEventArgs e) => {
			if (e.KeyCode == '\n' || e.KeyCode == CursesKey.ENTER) {
				callback (userInput);
			}

			if (e.KeyCode == '\n' || e.KeyCode == CursesKey.ENTER || e.KeyCode == CursesKey.ESC) {
				NCurses.SetCursor (0);
				NCurses.NoEcho ();
				
				inputHandler.DisableRawEventHandler (screen);

				NCurses.MoveWindow (screen, 0, 0);
				NCurses.DeleteWindow (inputFieldWin);
				NCurses.DeleteWindow (questionTextWin);
				NCurses.DeleteWindow (boxWin);
				NCurses.Refresh ();
			} else if (e.KeyCode == CursesKey.BACKSPACE) {
				userInput = userInput.Substring (0, userInput.Length - 2);
			} else if (char.IsAscii ((char) e.KeyCode)) {
				userInput += (char) e.KeyCode;
			}
			
			NCurses.MoveWindow (inputFieldWin, inputFieldWinY, inputFieldWinX);
		};

		inputHandler.EnableRawEventHandler (handlerFunction, inputFieldWin);
	}
}