Build a simple text editor

simple_text_editor.py

"""This is a simple script that simulates a text editor."""

import re
import os.path
from datetime import datetime


class TextEditor:
    """A tentative of representing a simple text editor.

    This class is a very simple tentative of representing a text
    editor, contains some methods for manipulating the text that
    will be edited.

    :attr current_text: This is the text that will be edited.
    :type current_text: str
    :attr undo_text: The "copy" of the current text that contains the
        last change made in current_text.
    :type undo_text: str
    """

    def __init__(self, current_text):
        self.current_text = current_text
        self.undo_text = None

    def __str__(self):
        """Returns the string representation of the current_text."""
        return self.current_text

    def append_text(self, text):
        """Appends text to the end of the current_text.

        :param text: The text that will be appended to the end of the
            current_text.
        :type text: str
        """
        self.undo_text = self.current_text

        self.current_text += text

    def insert_text(self, index, text):
        """Inserts text in the index of the current_text.

        :param index: The index that the text will be inserted.
        :type index: int
        :param text: The text that will be inserted in the index of the
            current_text.
        :type text: str
        """
        self.undo_text = self.current_text

        list_current_text = [char for char in self.current_text]
        list_current_text.insert(index, text)
        self.current_text = ''.join(list_current_text)

    def replace_word(self, old, new):
        """Replaces a old to a new word of the current_text.

        If the old word is not in the current_text, the process will be
        canceled.

        :param old: The word in current_text that will be
            replaced by new.
        :type old: str
        :param new: The word that will replace the old.
        :type new: str
        """
        self.undo_text = self.current_text

        pattern = re.compile(fr'\b{old}\b')
        if not old or pattern.search(self.current_text) is None:
            print(f'The word "{old}" is not in the current text.')
        else:
            self.current_text = pattern.sub(new, self.current_text, 1)

    def delete_text(self, num_chars=0):
        """Deletes the last num_chars of the current_text.

        :param num_chars: The number of the last characters that will be
            deleted (default is 0 (zero), that means "all characters of
            current_text will be deleted").
        :type num_chars: int
        """
        self.undo_text = self.current_text

        # Denies negative number of characters.
        num_chars = abs(num_chars)
        if num_chars == 0:
            self.current_text = ''
        else:
            self.current_text = self.current_text[:-num_chars]

    def undo_last_change(self):
        """Undo the last change made in the current_text.

        If no change was made in current_text, the process will be
        canceled.
        """
        if self.undo_text is None:
            print('No change was made in the current text yet.')
        else:
            self.current_text = self.undo_text

    def save_to_file(self, filename):
        """Saves the current_text to a text file.

        :param filename: The filename with extension (if you want to
            save the file in another directory, the full path of the
            file must be passed).
        :type filename: str
        """
        with open(filename, 'w') as f_obj:
            f_obj.write(self.current_text)

    def edit_from_file(self, filename):
        """Edits the text from a file.

        Replaces the current_text with the text from the file.

        If the file does not exist, the process will be canceled.

        :param filename: The filename with extension (if the file isn't
            in the same working directory, the full path of the file
            must be passed).
        :type filename: str
        """
        self.undo_text = self.current_text

        if not os.path.exists(filename):
            print(f"The file '{filename}' does not exist.")
        else:
            with open(filename) as f_obj:
                text = f_obj.read()
            self.current_text = text.rstrip()


def main():
    edit_text = TextEditor('')
    while True:
        print(f'\nCurrent text: "{edit_text}"')
        command = str(input('>>> ')).lower()

        if command == 'h':
            print("""\
                -> Text Editor Commands <-
            h -- show this help message
            a -- append text to the end of the current text
            i -- insert text in the index of the current text
            r -- replace a word of the current text
            d -- delete the last number of characters of the current text
            s -- save the current text in a text file
            e -- edit a text from a file
            u -- undo the last change
            q -- quit the text editor
            """.rstrip())

        elif command == 'a':
            text = str(input(f'\n[APPEND] ->{edit_text}'))
            edit_text.append_text(text)

        elif command == 'i':
            try:
                index = int(input('\n[INSERT] Index for insert: '))
            except ValueError:
                print('ERROR: expected a integer for the index.')
            else:
                current_text = edit_text.current_text
                text = str(input(f'[INSERT] ->{current_text[:index]}'))
                edit_text.insert_text(index, text)

        elif command == 'r':
            old_word = str(input('\n[REPLACE] Old word: '))
            new_word = str(input(f'[REPLACE "{old_word}"] New word: '))
            edit_text.replace_word(old_word, new_word)

        elif command == 'd':
            try:
                n = int(input('\n[DELETE] N° characters [0 to delete all]: '))
                edit_text.delete_text(n)
            except ValueError:
                print('ERROR: expected a integer for the n° of characters.')

        elif command == 's':
            filename = str(input('\n[SAVE TO FILE] Filename: /'))
            edit_text.save_to_file(filename)

            path = os.path.realpath(filename)
            dt_format = '%b %m %Y, %H:%M:%S'
            now = datetime.strftime(datetime.now(), dt_format)
            print(f"Saved on '{path}' - {now}")

        elif command == 'e':
            filename = str(input('\n[EDIT FROM FILE] Filename: /'))
            edit_text.edit_from_file(filename)

        elif command == 'u':
            edit_text.undo_last_change()

        elif command == 'q':
            print('Exiting the text editor...')
            break
        else:
            print("""\
                This is not a valid command.
            Please enter 'h' to see all available commands.
            """.rstrip())


if __name__ == '__main__':
    main()