#!/usr/bin/env python3
"""Todo.txt Manager - simple CLI todo list using todo.txt format."""

import sys
from pathlib import Path
from datetime import datetime
from typing import List

TODO_FILE = Path.home() / "todo.txt"


def read_todos() -> List[str]:
    """Read todos from file."""
    if not TODO_FILE.exists():
        return []
    return TODO_FILE.read_text().strip().split('\n') if TODO_FILE.read_text().strip() else []


def write_todos(todos: List[str]) -> None:
    """Write todos to file."""
    TODO_FILE.write_text('\n'.join(todos) + '\n')


def add_todo(task: str) -> None:
    """Add a new todo item."""
    todos = read_todos()
    todo = f"{datetime.now().strftime('%Y-%m-%d')} {task}"
    todos.append(todo)
    write_todos(todos)
    print(f"Added: {todo}")


def list_todos() -> None:
    """List all todos."""
    todos = read_todos()
    if not todos:
        print("No todos!")
        return
    
    for i, todo in enumerate(todos, 1):
        print(f"{i}. {todo}")


def done_todo(index: int) -> None:
    """Mark todo as done (remove it)."""
    todos = read_todos()
    if 1 <= index <= len(todos):
        removed = todos.pop(index - 1)
        write_todos(todos)
        print(f"Done: {removed}")
    else:
        print(f"Invalid index: {index}")


def clear_todos() -> None:
    """Clear all todos."""
    write_todos([])
    print("All todos cleared.")


def main():
    if len(sys.argv) < 2:
        list_todos()
        return
    
    cmd, args = sys.argv[1], sys.argv[2:]
    
    if cmd == "add" and args:
        add_todo(' '.join(args))
    elif cmd == "list":
        list_todos()
    elif cmd == "done" and args:
        done_todo(int(args[0]))
    elif cmd == "clear":
        clear_todos()
    else:
        print(f"Usage: {sys.argv[0]} [add <task>|list|done <num>|clear]")
        print("Simple TODO manager using todo.txt format at ~/todo.txt")


if __name__ == "__main__":
    main()