Text editor: typing, backspace, a cursor, and copy and paste

Context

Welcome to the notes app team. The editing core behind our text box has an agreed API in editor/text_editor.py, stubbed out, and the rules are in README.md.

Build levels 1 and 2 below in 25 minutes. The checks are graded one by one, so every method you get working counts even if the rest is not done.

EDIT-1: Typing and the cursor (level 1)

Acceptance criteria

• insert types at the cursor and leaves the cursor just after the new text.
• delete(count) works like backspace: it removes up to count characters before the cursor, and never more than there are.
• move_cursor keeps the cursor inside the document and returns where it ended up.
• get_text and get_cursor report the document and the cursor.

EDIT-2: Copy and paste (level 2)

Acceptance criteria

• copy(start, end) puts the text between two positions on the clipboard and returns it, without touching the text or the cursor.
• Positions outside the document are kept inside it. An empty selection empties the clipboard.
• paste types the clipboard at the cursor, as often as you like.

Notes

• Run pytest tests/visible. The hidden checks call the same methods with longer sequences of calls.
• Practice task modelled on candidate reports of text editor undo and redo rounds at Microsoft and Amazon. Original StackYard code, not the actual question; not affiliated with Microsoft or Amazon.