Command Pattern커맨드 패턴

Invoker → Command (execute/undo)
              ├── ConcreteCommand → Receiver
Client는 ConcreteCommand 생성 후 Invoker에 설정

from abc import ABC, abstractmethod
from dataclasses import dataclass, field

class Command(ABC):
    @abstractmethod
    def execute(self): pass
    @abstractmethod
    def undo(self): pass

class TextEditor:
    def __init__(self):
        self.content = ""

    def insert(self, text: str, pos: int):
        self.content = self.content[:pos] + text + self.content[pos:]

    def delete(self, pos: int, length: int):
        self.content = self.content[:pos] + self.content[pos+length:]

class InsertCommand(Command):
    def __init__(self, editor: TextEditor, text: str, pos: int):
        self.editor = editor
        self.text = text
        self.pos = pos

    def execute(self):
        self.editor.insert(self.text, self.pos)

    def undo(self):
        self.editor.delete(self.pos, len(self.text))

class CommandHistory:
    def __init__(self):
        self._history: list[Command] = []

    def execute(self, cmd: Command):
        cmd.execute()
        self._history.append(cmd)

    def undo(self):
        if self._history:
            self._history.pop().undo()

editor = TextEditor()
history = CommandHistory()

history.execute(InsertCommand(editor, "Hello", 0))
history.execute(InsertCommand(editor, " World", 5))
print(editor.content)  # Hello World

history.undo()
print(editor.content)  # Hello