TextField class using Kha in Haxe

TextField.hx

package render;

import kha.Key;
import kha.input.Keyboard;
import kha.Font;
import kha.Color;
import kha.input.Mouse;
import kha.graphics2.Graphics;

class TextField
{

	private var _keyboard:Keyboard;
	private var _caretIndex:Int;
	private var _keyDown:Bool;
	private var _minWidth:Int;

	public var caretPos(get, never):Int;
	function get_caretPos() return _caretIndex;

	public var defaultFont:Font;
	public var fontSize:Int;
	public var color:Color;
	public var text:String;
	public var x:Float;
	public var y:Float;
	
	private var _hasFocus:Bool;
	public var hasFocus(get, never):Bool;
	function get_hasFocus() return _hasFocus;

	private var _hasInput:Bool;
	public var hasInput(get, set):Bool;
	function get_hasInput() return _hasInput;
	function set_hasInput(val) return _hasInput = val;

	public var textWidth(get, never):Float;
	function get_textWidth()
	{
		var width = defaultFont.width(fontSize, text);
		if (width < _minWidth)
			width = _minWidth;

		return width;
	}

	public var textHeight(get, never):Float;
	function get_textHeight() 
	{
		return defaultFont.height(fontSize);
	}

	public function new()
	{
		fontSize = 12;

		_keyboard = Keyboard.get();
		_minWidth = 30;
		Mouse.get().notify(null, onMouseUp, null, null);

		hasInput = true;
		_caretIndex = 0;
		_keyDown = false;
	}

	public function render(g:Graphics): Void
	{
		g.font = defaultFont;
		g.fontSize = fontSize;

		if (color != null)
			g.color = color;
		else
			g.color = Color.White;
		
		g.drawString(text, x, y);
		
		if (_caretIndex > -1 && _hasFocus && _hasInput)
		{
			var subTextToCaret = text.substr(0, _caretIndex);
			var subTextLength:Float = 0;
			if (subTextToCaret != "")
				subTextLength = defaultFont.width(fontSize, subTextToCaret);
			
			var textHeight = defaultFont.height(fontSize);

			g.color = Color.White;
			g.drawLine(x + subTextLength, y, x + subTextLength, y + textHeight);
		}
	}

	private function onMouseUp(button:Int, mouseX:Int, mouseY:Int):Void
	{
		if (button > -1)
		{
			if (mouseX > this.x && mouseY > this.y && mouseX < this.x + textWidth && mouseY < this.y + textHeight)
			{
				_keyboard.notify(onKeyDown, onKeyUp);
				_hasFocus = true;
			}
			else
			{
				_keyboard.remove(onKeyDown, onKeyUp);
				_hasFocus = false;
			}
		}
	}

	private function onKeyDown(key:Key, char:String):Void
	{
		
	}

	private function onKeyUp(key:Key, char:String):Void
	{
		if (!_hasInput)
			return;

		switch(key)
		{
			case CHAR:
				

				if (_caretIndex < text.length)
				{
					if (_caretIndex == 0)
					{
						text += char;
						_caretIndex++;
					}
					else
					{
						var leftText = text.substr(0, _caretIndex);
						var rightText = text.substr(_caretIndex);

						leftText += char;
						
						text = leftText + rightText;
						_caretIndex = leftText.length;
					}
				}
				else
				{
					if (_caretIndex > 0)
					{
						text += char;
						_caretIndex = text.length;
					}
					else
					{
						text = char;
						_caretIndex = 1;
					}
				}
			case ALT:
			case BACK:
			case BACKSPACE:
				if (_caretIndex > 0 && _caretIndex < text.length)
				{
					var leftText = text.substr(0, _caretIndex - 1);
					var rightText = text.substr(_caretIndex);

					text = leftText + rightText;
					_caretIndex = leftText.length;
				}
				else
				{
					if (_caretIndex != 0)
					{
						text = text.substr(0, text.length - 1);
						_caretIndex--;
					}
				}
			case CTRL:
			case DEL:
			case DOWN:
			case ENTER:
			case ESC:
			case LEFT:
				if (_caretIndex - 1 < 0)
					_caretIndex = 0;
				else
					_caretIndex--;
			case RIGHT:
				if (_caretIndex + 1 > text.length)
					_caretIndex = text.length;
				else
					_caretIndex++;
			case SHIFT:
			case TAB:
			case UP:
		}
	}

}