Word Count Validator

Objective

Recently the internet has exploded to reach across the galaxy. There is a hostile species of troll aliens that have started infesting the internet with disruptive, angry comments on internet forums. Scientists have determined that the troll aliens are really bad at counting words. Thus they have tasked you with creating a type of CAPTCHA for troll aliens to keep them out of the forums. Trying to be helpful, the scientists have sent along some starter code. It's not complete and some things could probably be done better. To run the scientists' starts code:

    # You can get everything installed using
    bundle install

    # Run the server using
    ruby app.rb

    # Run the test suite via
    rspec

Description

We want to verify that a client can count words. As such, we need a web service that supplies clients with a "test" and allows the client to submit an answer. If the client and the service were people, their conversation might go something like this:

Client: Service, can you give me some words to count?

Service: Sure. Please count the frequency of the words in "The quick brown fox jumped over the lazy dog" but please ignore the words "the" and "dog".

Client: Ok, the original text was "The quick brown fox jumped over the lazy dog" and in this text, ignoring the words "the" and "dog", "quick" appeared once, "brown" appeared once, "fox" appeared once, "jumped" appeared once, "over" appeared once, "lazy" appeared once, and "the" appeared twice.

Service: Sorry, that's wrong. Nice try space troll.

Client: Oops, what I meant was the original text was "The quick brown fox jumped over the lazy dog" and in this text, ignoring the words "the" and "dog", "quick" appeared once, "brown" appeared once, "fox" appeared once, "jumped" appeared once, "over" appeared once, and "lazy" appeared once.

Service: Looks great.

Requirements

Write a server that does 2 things

1. Respond to a client HTTP request

Respond to a client HTTP request with at least the following in the response body:

1. A random body of text. Some sample texts are included.
2. A list of some but not all words in that body of text (exception: texts with only one unique word should use an empty list)

2. Receive a client HTTP request

Receive a client HTTP request with at least the following in the request

1. A body of text
2. A list of some but not all words in that body of text (exception: texts with only one unique word should have an empty list)
3. A count of the frequency of every word in the body of text excluding words from the list

and respond with:

1. If the word frequency count is correct, then 200 OK
2. If the word frequency count is incorrect or the request is otherwise invalid, then 400 Bad Request

You are not required to write the client application, but you can assume that a client for this server should:

1. Request from 1
2. Count the frequency of each word in the given body of text minus all of the given exclusion words
3. Send to 2 the word frequency count result with the original response body from 1.

Readme

Writing software in a fast-paced, independent environment involves discovering and resolving many ambiguities. Your ability to make good assumptions and trade-offs is key. Keep the objective of the assignment in mind when making such decisions. Please include a readme document in your submission that describes any assumptions or decisions.

Tests

Quality assurance is very important for maintaining a successful defense against the alien trolls. Please include a means to automatically assert the correctness of your code. This can be unit tests that validate the correctness of individual small pieces of code or functional tests that verify expected responses from particular endpoints. However you choose to implement tests, it must be automated and simple to run. It should not be a matrix of complicated human-driven steps and comparisons.

Guidelines

0. Please do not create a public fork this repository. Rather, you can submit a git package, a zip file, or a private fork.
1. You should feel free to write your solution in whichever language you are most comfortable writing.
2. Style, algorithms, data structures, request/response format, etc. are all up to you. However, keep in mind that we will be looking at these choices.
3. If your service can run on a Unix environment (e.g. ) Mac OSX, then please include the following:
   1. Any installation instructions or notes to set up our Mac OSX laptops to run your server
   2. A script ./run to start the server
   3. The server should run on localhost:8000 and serve a single path /
4. If your service cannot run on Mac OSX, then please run your server on a remote host and provide us the hostname, port, and path to access it.
5. An open ended task like this can be expanded and improved infinitely. One could work on it forever, continously making little tweaks here and there. Meanwhile, alien trolls continue to terrorize the internet. This project should take a few hours, but certainly no more than 8. Please set a maximum amount of time to work on this project and submit whatever you have by the end of that time window. If you have not finished to your own satisfaction, please explain everything that you would like to add in your Readme.
6. Treat this assignment as you would an actual work project and write code as you would in the actual work place. Please do not write code as you would for a research project in a theoretical quantum computer or as a proof of P=NP.

Bonus

1. Cheating Protection: When the server receives text, exclusion words, and a word count from the client, it verifies that the text and exclusion words that it previously gave a client.
2. Stateless/Idempotent: Remove as much "state" as possible from the server. Any new request to the server does not depend on the state of a previous request.