#!/usr/bin/python3

from PyQt6.QtWidgets import QPlainTextEdit
from PyQt6.QtCore import Qt


class BinaryTextEdit(QPlainTextEdit):  # rewrite QPlainTextEdit.keyPressEvent because it has no .setValidator()
    def keyPressEvent(self, event):
        allowed_keys = {"", "0", "1"}

        if event.text() in allowed_keys:
            cursor = self.textCursor()
            position = cursor.position()
            text = self.toPlainText()
            text_length = len(text)

            if not (position + 1) % 9 == 0 or event.text() in {"", None}:  # dont overwrite the separator character
                super().keyPressEvent(event)

            # skip over the separator character when the cursor is right before it.
            if (position + 2) % 9 == 0 and not event.text() in {"", None}:
                if position == text_length - 1:  # append to the input if the cursor is at the end
                    self.insertPlainText(" 00000000")

                cursor.setPosition(position + 2)
                self.setTextCursor(cursor)

        elif event.key() == Qt.Key.Key_Backspace or event.key() == Qt.Key.Key_Delete:
            # delete last byte when backspace or delete is pressed
            text = self.toPlainText()

            if len(text) >= 9:
                cursor = self.textCursor()
                position = cursor.position()

                text = text[:-9]  # delete last byte

                self.setPlainText(text)

                # calculate the new cursor position (by subtracting 9, we set the position to the same bit but one byte
                # before and by floor dividing this by 9 we get the "byte index" and when we multiply this by 9, we get
                # the character position of the first bit in that byte.)
                position = (position - 9) // 9 * 9

                cursor.setPosition(position)

                self.setTextCursor(cursor)

        else:
            event.ignore()