Paginated JIRA query in Ruby

query_jira.rb

require 'json'
require 'csv'

### This is a function definition; functions are the same kind of thing you
### use in excel, like VLOOKUP - you give them a variable and they do something
### or return some variable; this one is simple, you give it a URL and it
### returns a command to be run in a shell
def make_query(url)
  ### This makes the request to the url you've requested; think about it as a
  ### browser window that does things for you and returns you data / html / etc
  ### Note: the parameters of this curl request are missing; the easiest way
  ### to get these is to use the chrome "Copy as CURL" feature
  return %{curl '#{url}'}
end

### This is another function definition; Jira only returns you stuff in chunks
### of 50; so you have to do a series of requests, one after another, and
### continually accumulate the result into one variable; this function does just
### that
def paginated_query(uri, params="", accumulator=[])

  ### This line makes a request to the JIRA Rest API and puts it in a data
  ### structure that can be access later, called "results"
  results = JSON.parse(`#{make_query(uri + params)}`)

  ### Accumulator is the variable I mentioned above where we keep shoving items
  ### into; here we do just that, we add whatever the rest API returned to it
  accumulator += results["issues"]

  ### Below is a branch; it tells us whether we do what's on the next line or
  ### not; in this particular case, we're checking if the accumulator includes
  ### all items in the filter provided or not
  if(accumulator.length < results["total"])
    ### This is a bit tricky; this makes another request to the same function
    ### we're in, but passes some extra variables so that JIRA returns us items
    ### that are further along in the stack, and keeps accumulating them
    accumulator = paginated_query(uri, "&startAt=#{results["startAt"] + results["maxResults"]}", accumulator)
  end

  ### This sends the accumulator we've been creating out of the function we've
  ### called
  return accumulator
end

### The part above is just preparation; this is where we actually call the
### function and take all the items returned from JIRA and put them in a
### variable called results
results = paginated_query("https://jira-website.here/rest/api/3/search?jql=filter=32434")

### Here it's actually quite easy, we use the CSV library to start editing
### a CSV file called "output.csv"
CSV.open("./output.csv", "wb") do |csv|
  ### We put in the "output.csv file" a summary and story points header
  csv << ["summary", "story points"]

  ### We then go through all the issues return from JIRA and put their summary
  ### and story points into the csv one at the time
  results.each_with_index do |issue, index|
    csv << [issue["fields"]["summary"], issue["fields"]["customfield_10002"]]
  end
end