task_cli.py

"""
Task Tracker CLI - 项目骨架
用法示例:
    python task_cli.py add "买菜"
    python task_cli.py list
    python task_cli.py update 1 "买菜和做饭"
    python task_cli.py mark-done 1
    python task_cli.py delete 1
"""

import sys
import json
import os
from datetime import datetime

# 存储任务的文件名
TASKS_FILE = "tasks.json"


# ========== 核心工具函数 ==========

def load_tasks():
    """读取所有任务。如果文件不存在,返回空列表。"""
    if not os.path.exists(TASKS_FILE):
        return []
    with open(TASKS_FILE, "r", encoding="utf-8") as f:
        # 处理空文件的情况
        content = f.read().strip()
        if not content:
            return []
        return json.loads(content)


def save_tasks(tasks):
    """把任务列表写回文件。"""
    with open(TASKS_FILE, "w", encoding="utf-8") as f:
        json.dump(tasks, f, ensure_ascii=False, indent=2)


def now():
    """返回当前时间的 ISO 格式字符串。"""
    return datetime.now().isoformat(timespec="seconds")


# ========== 命令实现函数 ==========

def add_task(description):
    """添加一个新任务。"""
    tasks = load_tasks()

    # TODO 1: 生成新 ID
    # 提示: 找出 tasks 里最大的 id, 加 1; 如果列表是空的就用 1
    new_id = max([t["id"] for t in tasks], default=0) + 1

    # TODO 2: 构造新任务字典
    # 需要的字段: id, description, status (初始为 "todo"), createdAt, updatedAt
    new_task = {
        "id":new_id,
        "description":description,
        "status":"todo",
        "createdAt":now(),
        "updatedAt":now()
    }  # ← 在这里实现

    tasks.append(new_task)
    save_tasks(tasks)
    print(f"Task added successfully (ID: {new_id})")


def update_task(task_id, new_description):
    """更新指定 ID 任务的描述。"""
    tasks = load_tasks()

    # TODO 3: 遍历 tasks, 找到 id 匹配的那一个
    # 找到了: 修改它的 description, 更新 updatedAt, 保存, 打印成功
    # 没找到: 打印 "Task not found"
    # 提示: 用 for 循环, 或者更优雅的写法 next((t for t in tasks if t["id"] == task_id), None)
    task = next((t for t in tasks if t["id"] == task_id), None)
    if task:
        task["description"] = new_description
        task["updatedAt"] = now()
        save_tasks(tasks)
        print("Task updated successfully")
    else:
        print("Task not found")


def delete_task(task_id):
    """删除指定 ID 的任务。"""
    tasks = load_tasks()

    # TODO 4: 从 tasks 中移除 id 匹配的任务
    # 提示: 可以用列表推导 [t for t in tasks if t["id"] != task_id]
    # 记得判断: 如果新列表长度和原来一样, 说明没找到, 提示用户
    new_tasks = [t for t in tasks if t["id"] != task_id]
    if len(new_tasks) == len(tasks):
        print("Task not found")
    else:
        save_tasks(new_tasks)
        print("Task deleted successfully")


def mark_task(task_id, new_status):
    """把任务标记为指定状态 (in-progress 或 done)。"""
    tasks = load_tasks()

    # TODO 5: 类似 update_task, 但改的是 status 字段
    task = next((t for t in tasks if t["id"] == task_id), None)
    if task:
        task["status"] = new_status
        task["updatedAt"] = now()
        save_tasks(tasks)
        print("Task status updated successfully")
    else:
        print("Task not found")


def list_tasks(filter_status=None):
    """列出任务。filter_status 为 None 时列出全部, 否则按状态过滤。"""
    tasks = load_tasks()

    # TODO 6: 如果 filter_status 不是 None, 只保留 status == filter_status 的任务
    # 然后把每个任务打印出来 (id, description, status, 时间)
    # 如果列表为空, 打印 "No tasks found"
    filtered_tasks = [t for t in tasks if t["status"] == filter_status] if filter_status else tasks
    if not filtered_tasks:  
        print("No tasks found")
        return
    for t in filtered_tasks:        
        print(f"ID: {t['id']}, Description: {t['description']}, Status: {t['status']}, Created At: {t['createdAt']}, Updated At: {t['updatedAt']}")
    return
         # ← 在这里实现


# ========== 命令分发 ==========

def main():
    # sys.argv[0] 是脚本名, sys.argv[1] 是第一个真正的参数
    args = sys.argv[1:]

    if len(args) == 0:
        print("Usage: python task_cli.py <command> [arguments]")
        print("Commands: add, update, delete, list, mark-in-progress, mark-done")
        return

    command = args[0]

    try:
        if command == "add":
            if len(args) < 2:
                print("Error: please provide a task description")
                return
            add_task(args[1])

        elif command == "update":
            if len(args) < 3:
                print("Error: usage: update <id> <new description>")
                return
            update_task(int(args[1]), args[2])

        elif command == "delete":
            if len(args) < 2:
                print("Error: please provide a task ID")
                return
            delete_task(int(args[1]))

        elif command == "mark-in-progress":
            mark_task(int(args[1]), "in-progress")

        elif command == "mark-done":
            mark_task(int(args[1]), "done")

        elif command == "list":
            if len(args) == 1:
                list_tasks()
            else:
                status = args[1]
                # 题目里 "todo" 对应未完成, 注意这里要和你存的 status 值对应
                if status not in ("todo", "in-progress", "done"):
                    print(f"Error: unknown status '{status}'")
                    return
                list_tasks(status)

        else:
            print(f"Error: unknown command '{command}'")

    except ValueError:
        print("Error: ID must be a number")
    except Exception as e:
        print(f"Error: {e}")


if __name__ == "__main__":
    main()