Flask Server Challenge

Aki wants to plan the next developers meetup. As tasks stack up, he thinks that a todo list app might help him manage the event better.

He recalls he had frontend for a simple Android ToDo List App he developed in a previous dev meet. But he lacks the backend for it. Since he has a lot of work to do, he can't develop the server so soon.

You may develop the solutions in groups.

Before starting this challanage Register yourself here

Task

Help Aki by developing a simple Flask web server for him ToDo list app.

Level 0 - Easy - Flask basics

Create a simple Flask server with two basic methods

API End Point	Type	Required Body Params	Required Return Value
/sample_get	GET	NA	String "Hello Flask" without quotes
/sample_post	POST	name(string)	String "Hello to Flask, ", where name is supplied as a POST parameter

Level 1 - Easy - Database Intregration

Create a simple Flask server that with some basic methods - maintain a serial list of tasks(numbered 1,2,3...). You're free to keep the database local or hosted somewhere.

API End Point	Type	Body Params	Return value(apart from status)	Description
/list_all	GET	NA	task{}(list of strings)	Get the list of tasks to be done
/append	POST	task(string)	NA	Append a task to the list
/insert	POST	task(string), index(int)	NA	Insert a task between indices (index,index+1)
/get	GET	index(int)	task(string)	Return task at given index
/delete	DELETE	index(int)	task(string)	Delete task at given index. Return the deleted task

Level 2 - Medium - Speech to Text

Aki thinks dictation will be faster typing. So he wants to store tasks via voice.

There are many engines available for speech to text conversion(follow this article for a complete list). You need to add a new features to create a task using speech.

API End Point	Type	Body Params	Return value(apart from status)	Description
/append_speech	POST	audio_task(base64 encoded string)	NA	Append a task to the list
/insert_speech	POST	audio_task(base64 encoded string), index(int)	NA	Insert a task between indices (index,index+1)

Note: Refer resources for details about base64. Its important for sending media data over REST APIs

Level 3 - Medium - File Hosting

Aki wants to clip additional data with a task, like an image memo or a PDF invoice.

Adapt the existing endpoints to meet the requirements. Now tasks are no longer strings, but a custom data type.

object Task:
    string task
    string meta-data-url = "" // by default empty

And the end points are changed as follows(with usual meanings)

API End Point	Type	Body Params	Return value(apart from status)
/list_all	GET	NA	task{}(list of Task objects)
/append	POST	task(string), meta-data(base64 encoded data)	NA
/insert	POST	task(string), meta-data(base64 encoded data) ,index(int)	NA
/get	GET	index(int)	task(Task object)
/delete	DELETE	index(int)	task(Task object)

Level 4 - Hard - Caching database

Memcached is a general purpose caching system. There are many levels of caching - file caching , data caching, etc.

You're task is to cache the database only for /get and /list_all endpoints. We advise using a python libary for this purpose. If you've implemented it correctly, then you're server should withstand a large number of requests(say 10,000 request per sec).

Level 5 - Very Hard - Undo/Redo Features

Aki types really bad(thats why he prefer to use voice). And also he prefers undoing typing a task rather than correcting it.

Manage the history of tasks entered and deleted. In this sense, undo means going one step back in history(which might mean deleting a task or restoring a deleted task) and redo means one step in future. This might seem easy at first glance, but you'll need to develop a mini git of your own!. There are many ways to version data. Refer this and this article for more.

API End Point	Type	Body Params	Return value(apart from status)	Description
/undo	GET	NA	task{}(list of strings)	List of tasks viewed as one step back in history
/redo	GET	NA	task{}(list of strings)	List of tasks viewed as one step ahead in future

Note: You can't undo with no tasks. Similarly, you can't redo when already at the lastest list of tasks.

Evaluation Criteria

There's no marking criteria(Remember you're just hepling Aki, Cheers! ;D ). The levels arranged in increasing order of difficulty. For testing purposes, keep your file structured in such a way that the main serving file is named app.py or the evaluators should be able to run server using the following commands:

export FLASK_APP=app.py
flask run

Resources

• Intro to Flask - https://www.fullstackpython.com/flask.html
• Handling REST Requests - https://scotch.io/bar-talk/processing-incoming-request-data-in-flask
• Flask Auth - https://realpython.com/token-based-authentication-with-flask/
• Flask DB Introducion - http://flask-sqlalchemy.pocoo.org/2.3/quickstart/
• Flask Postgres - https://blog.theodo.fr/2017/03/developping-a-flask-web-app-with-a-postresql-database-making-all-the-possible-errors/
• Google Text to Speech API in Python - https://www.geeksforgeeks.org/convert-text-speech-python/
• Flask Caching - https://realpython.com/python-memcache-efficient-caching/
• Uploading Files via HTTP requests - https://medium.com/@petehouston/upload-files-with-curl-93064dcccc76
• Base64 encoding - https://cloud.google.com/speech-to-text/docs/base64-encoding

More Info

• You need not host the server
• The body content should be json encoded.
• status param is mandatory for all end points. Its value is 200 for success, 404 for URL not found, etc. Refer this doc for a complete list.