An example todos app with DDD approach

• http://blog.cleancoder.com/uncle-bob/2012/08/13/the-clean-architecture.html
• https://hackernoon.com/making-a-case-for-domain-modeling-17cf47030732
• https://medium.com/swlh/creating-coding-excellence-with-domain-driven-design-88f73d2232c3
• https://www.javacodegeeks.com/2016/10/architectural-layers-modeling-domain-logic.html
• https://www.alibabacloud.com/blog/handling-complex-business-scenarios-with-domain-modeling-%E2%80%93-part-1_593863?spm=a2c65.11461447.0.0.acc85f82jfZ0Us

• User will be logged in by providing a username (no need password, no need to register)
• User could manage one ore more todo task items
• Each task's state could be as follow: new -> doing -> done
• To stay focused, user could only have 3 doing tasks at a time. But if he has finished at least 3 tasks in his lifetime usage, he could have up to 5 concurrent doing tasks
• User could delete/remove any task in the list
• No need to manage task creation time

1. Get all tasks of user

GET /tasks

Request
--------
Header::Authorization: Bearer <username>

Response
--------
[
    { "taskid": "abc...", "description": "...", "status": "..." },
    { "taskid": "xyz...", "description": "...", "status": "..." }
]

2. Add task

POST /tasks

Request
-------
Header::Authorization: Bearer <username>
Header::Content-Type: application/json
Body: {
    "description": "new task"
}

3. Update task status

PUT /tasks/<task_id>/status

Request
-------
Header::Authorization: Bearer <username>
Header::Content-Type: application/json
Body: {
    "status": 1  # 1: doing; 2: done
}

• Now, we need to manage the emergency of a task (true or false)
• To keep focused, each user could only have 3 doing tasks at a time, but if he has a really urgent task, he could add 1 and only 1 emergency task to having 4 concurrency doing tasks
• If a user has finished at least 3 tasks in his lifetime usage, he could have up to 5 concurrent doing tasks

Collection User {
    username: "joe",
    tasks: [
        {
            id: "...",
            desc: "...",
            state: "...",
            emergency: 1  # 1: yes; 0: no
        }, {
            ...
        }
    ]
}