JsonApi Assessment

Starting from a new Phoenix project, you’ll need to implement the following:

1. A JSON endpoint to add new repositories to the system.
2. The ability to retrieve and store stargazers for tracked repositories using the Github API.
   This will be run daily.*
3. Add a second JSON endpoint to return a list of new and former stargazers given a date range and repository.

• Implementation of the actual scheduling isn't necessary but we would like to know in your README how you would handle this.

LOGIC behind the code:

- StargazersController "/add_new_repo" endpoint:

1. We are checking if user + repo_name combination already exists/saved in the system. If NOT we are calling Github API endpoint https://api.github.com/repos/#{username}/#{repo_name}/stargazersto make sure user + repo_name valid and if yes we are collecting all stargazers.
2. We are saving all new user + repo_name combination into ETS table :users even if that repo has ZERO stars:
   {username, repo_name}.
3. If user's repo has STARS we are saving all starred users into ETS table :stargazers:
   {"username", "repo_name", {"stargazer_name", "2021-01-24", "starred"}}

- StargazersController "/new_and_former_stargazers" endpoint:

1. Since all stargazers already saved in our db, we just need to get that information providing this payload:

{
    "username": "a username",
    "repo": "repo name",
    "start_range": "2011-01-07T00:00:00Z",
    "end_range": "2021-01-26T23:59:59Z"
}

- cron.ex (will be implemented by Quantum)

1. Hypothetically, at 6am getting all users from :users ETS table specifying this in our config.ex:

config :eltoro_api, JsonApi.Scheduler,
  jobs: [
    #  6am everyday (time in UTC)
    {"0 10 * * *", {JsonApi.Cron, :run, []}}
  ]

and application.ex:

    :ets.new(:users, [:bag, :public, :named_table])
    spawn(fn -> JsonApi.Cron.run() end)

    :ets.new(:stargazers, [:bag, :public, :named_table])
    spawn(fn -> JsonApi.Cron.run() end)

2. calling Github API endpoint with user's information to get stargazers for all users(those repos without stars yesterday might have stars)
3. Filtering those ones without stars and getting new starred and ustarred users
4. Comparing old data (what was in db) and new data (just got it from Github API call), merging all together and saving updated data into the ETS table :stargazers, basically preparing data for "/new_and_former_stargazers" endpoint

---

HOW TO TEST

- StargazersController "/add_new_repo" endpoint:

1. Run: make setup_app

2. Start the app: make start_app

3. POSTMAN collection folder has a correct request form or curl down below:

curl --location --request POST 'http://localhost:4000/api/add_new_repo' \
--header 'Content-Type: application/json' \
--data-raw '{
    "username": "octocat",
    "repo": "hello-world"
}'

or any repo... (experiment with starred and unstarred repos)

4. Star the same repo if it was unstarred

5. in iex run this alias JsonApi.Cron and then Cron.run this module will be triggered as a cron job by Quantum(not implemented yet, but super easy to do it) every morning, so running it from iex will be a clear representation for the cron job we expect
   So you should see yourself in the ETS table with a flag starred

6. Do opposite of #3 and run again #4: if you were starred before you should see yourself as unstarred (give some time before Cron.run: GitHub API is not picking up information quickly)

- StargazersController "/new_and_former_stargazers" endpoint:

curl --location --request POST 'http://localhost:4000/api/new_and_former_stargazers' \
--header 'Content-Type: application/json' \
--data-raw '{
    "username": "octocat",
    "repo": "hello-world",
    "start_range": "2011-01-07T00:00:00Z",
    "end_range": "2021-01-26T23:59:59Z"
}'

if a user octacat and hello-world repo not in the system you'll get a message saying, that user not in the system and you need to add them first. As soon as they added you run a request from POSTMAN collection or curl above. Expect this response:

{
    "body": [
        "schacon starred",
        "adelcambre starred",
        "usergenic starred",
        "fdb starred",
        "darinel starred",
        "Willianvdv starred",
        "sul4bh starred",
        "preavy starred",
        "benjic starred",
        "hagiwaratakayuki starred",
        "stefanlasiewski starred",
        "hbjerry starred",
        "Visgean starred",
        "jiska starred",
        "hittudiv starred",
        "paulomichael starred",
        "garbagemonster starred",
        "minamipj9 starred",
        "coolhead starred",
        "Spaceghost starred",
        "RustyF starred",
        "chexee starred",
        "adrianbarbic starred",
        "yasirmturk starred",
        "moonshadows starred",
        "ff6347 starred",
        "LunaticNeko starred",
        "saadrehman starred",
        "allanmaio starred",
        "kapare starred"
    ],
    "errors": null
}

- For local tests: mix test test/json_api_web/controllers/stargazers_controller_test.exs

---

MAIN challenge of the assessment

Looks like GitHub API doesn't have a specific endpoint to track unstarred stargazers. So the main idea in my implementation is:
COMPARE old data (was collected yesterday by cron job or when starred repo was saved manually through the first endpoint) against new data (collected this morning by cron job). If it exists ONLY in old data, I need update that record to unstarred and timestamp should be updated to - 1 day. I left some logs for the Cron.run execution to make it more clear what I mean.