#!/usr/bin/python3

from PyQt6.QtWidgets import QPlainTextEdit


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()
            pos = cursor.position()
            text = self.toPlainText()
            text_length = len(text)

            if not (pos + 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 before it.
            if (pos + 2) % 9 == 0 and not event.text() in {"", None}:
                if pos == text_length:  # append to the input if the cursor is at the end
                    self.insertPlainText("  ")
                    cursor = self.textCursor()
                    cursor.setPosition(pos + 2)

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

        else:
            event.ignore()