In the previous two chapters, we explored the GitHub API, learning how to query the API and parse the results using json-4s.
Let's imagine that we want to extract the GitHub follower graph: we want a program that will start from a particular user, extract this user followers, and then extract their followers until we tell it to stop. The catch is that we don't know ahead of time what URLs we need to fetch: when we download the login names of a particular user's followers, we need to verify whether we have fetched these users previously. If not, we add them to a queue of users whose followers we need to fetch. Algorithm aficionados might recognize this as breadth-first search.
Let's outline how we might write this in a single-threaded way. The central components are a set of visited users and queue of future users to visit:
val seedUser = "odersky" // the origin of the network // Users whose URLs need to be fetched val queue = mutable.Queue(seedUser) // set of users...
