Design command executor with undo

Problem Statement

Design a command executor system that manages the state of a simple text document. The system must support performing operations (commands) and rolling them back (undo).

Implement the CommandExecutor class, which manages a document represented as a single string. You need to implement the following operations:

1. execute(command): Executes a command and stores it in a history log.
2. undo(): Reverses the last successfully executed command and removes it from the history.

Define an interface Command that contains the following methods:

• execute(current_state) -> new_state
• undo(current_state) -> previous_state

Requirements

• The system should maintain a history of commands performed.
• If an undo() is called when the history is empty, the system should do nothing.
• The state of the document is a single string.

Example

# Assume a command that appends a string
class AppendCommand:
    def __init__(self, text_to_add):
        self.text_to_add = text_to_add
    def execute(self, state): return state + self.text_to_add
    def undo(self, state): return state[:-len(self.text_to_add)]

executor = CommandExecutor()
executor.execute(AppendCommand("Hello"))
executor.execute(AppendCommand(" World"))
# Current state: "Hello World"
executor.undo()
# Current state: "Hello"

Constraints

• Commands should be atomic.
• The history can grow indefinitely; consider memory management if necessary.
• Handle cases where the document state might be empty.