task_manager.py

#!/usr/bin/env python3
"""
Task Manager - A simple CLI task management application.
Supports adding, listing, completing, and deleting tasks with persistence via JSON.
"""

import json
import os
import sys
from datetime import datetime


DATA_FILE = os.path.join(os.path.dirname(__file__), "tasks.json")


def load_tasks() -> list[dict]:
    if not os.path.exists(DATA_FILE):
        return []
    with open(DATA_FILE, "r") as f:
        return json.load(f)


def save_tasks(tasks: list[dict]) -> None:
    with open(DATA_FILE, "w") as f:
        json.dump(tasks, f, indent=2)


def add_task(title: str) -> None:
    tasks = load_tasks()
    task = {
        "id": (max((t["id"] for t in tasks), default=0) + 1),
        "title": title,
        "done": False,
        "created_at": datetime.now().isoformat(),
    }
    tasks.append(task)
    save_tasks(tasks)
    print(f"[+] Task {task['id']} added: {title}")


def list_tasks(show_all: bool = False) -> None:
    tasks = load_tasks()
    if not tasks:
        print("No tasks found. Add one with: python task_manager.py add <title>")
        return

    filtered = tasks if show_all else [t for t in tasks if not t["done"]]
    if not filtered:
        print("All tasks are done! Great job.")
        return

    print(f"\n{'ID':<5} {'Status':<10} {'Title'}")
    print("-" * 50)
    for t in filtered:
        status = "✓ done" if t["done"] else "○ todo"
        print(f"{t['id']:<5} {status:<10} {t['title']}")
    print()


def complete_task(task_id: int) -> None:
    tasks = load_tasks()
    for task in tasks:
        if task["id"] == task_id:
            if task["done"]:
                print(f"Task {task_id} is already marked as done.")
            else:
                task["done"] = True
                save_tasks(tasks)
                print(f"[✓] Task {task_id} marked as complete: {task['title']}")
            return
    print(f"Task {task_id} not found.")


def delete_task(task_id: int) -> None:
    tasks = load_tasks()
    remaining = [t for t in tasks if t["id"] != task_id]
    if len(remaining) == len(tasks):
        print(f"Task {task_id} not found.")
        return
    save_tasks(remaining)
    print(f"[-] Task {task_id} deleted.")


def print_usage() -> None:
    usage = """
Task Manager - Simple CLI Todo App

Usage:
  python task_manager.py add <title>      Add a new task
  python task_manager.py list             List pending tasks
  python task_manager.py list --all       List all tasks (including done)
  python task_manager.py done <id>        Mark a task as complete
  python task_manager.py delete <id>      Delete a task
  python task_manager.py help             Show this help message
"""
    print(usage)


def main() -> None:
    args = sys.argv[1:]

    if not args or args[0] == "help":
        print_usage()
        return

    command = args[0]

    if command == "add":
        if len(args) < 2:
            print("Error: provide a task title. Example: python task_manager.py add 'Buy milk'")
            sys.exit(1)
        add_task(" ".join(args[1:]))

    elif command == "list":
        show_all = "--all" in args
        list_tasks(show_all)

    elif command == "done":
        if len(args) < 2 or not args[1].isdigit():
            print("Error: provide a valid task ID. Example: python task_manager.py done 1")
            sys.exit(1)
        complete_task(int(args[1]))

    elif command == "delete":
        if len(args) < 2 or not args[1].isdigit():
            print("Error: provide a valid task ID. Example: python task_manager.py delete 1")
            sys.exit(1)
        delete_task(int(args[1]))

    else:
        print(f"Unknown command: {command}")
        print_usage()
        sys.exit(1)


if __name__ == "__main__":
    main()