Find people who do not follow you back on GitHub.

github-unfollowers.go

// Package main is a CLI runner to run this script ('github-unfollowers.go').
// This script is used to get a user's 'unfollowers' - which means people who do not follow that user's back.
// You do not need GitHub Tokens, as all the endpoints are public. Use this with responsibility though, do not spam.
//
// How to run: copy this script to a workspace, place your username, then run 'go run github-unfollowers.go'
// You can place your username by using 'export GITHUB_USERNAME=YOUR_GITHUB_USERNAME' or by editing the source code and filling it manually.
//
// Author & License: Nicholas (MIT)
package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"math"
	"net/http"
	"os"
	"strings"
)

// Social is a struct representative of 'Followers' and 'Following' entity from the API.
type Social struct {
	Login             string `json:"login"`
	ID                uint64 `json:"id"`
	NodeID            string `json:"node_id"`
	AvatarURL         string `json:"avatar_url"`
	GravatarID        string `json:"gravatar_id"`
	URL               string `json:"url"`
	HTMLURL           string `json:"html_url"`
	FollowersURL      string `json:"followers_url"`
	FollowingURL      string `json:"following_url"`
	GistsURL          string `json:"gists_url"`
	StarredURL        string `json:"starred_url"`
	SubscriptionsURL  string `json:"subscriptions_url"`
	OrganizationsURL  string `json:"organizations_url"`
	ReposURL          string `json:"repos_url"`
	EventsURL         string `json:"events_url"`
	ReceivedEventsURL string `json:"received_events_url"`
	Type              string `json:"type"`
	SiteAdmin         bool   `json:"site_admin"`
}

// User is a struct representative of 'User' data from GitHub's API.
type User struct {
	Login             string `json:"login"`
	ID                uint64 `json:"id"`
	NodeID            string `json:"node_id"`
	AvatarURL         string `json:"avatar_url"`
	GravatarID        string `json:"gravatar_id"`
	URL               string `json:"url"`
	HTMLURL           string `json:"html_url"`
	FollowersURL      string `json:"followers_url"`
	FollowingURL      string `json:"following_url"`
	GistsURL          string `json:"gists_url"`
	StarredURL        string `json:"starred_url"`
	SubscriptionsURL  string `json:"subscriptions_url"`
	OrganizationsURL  string `json:"organizations_url"`
	ReposURL          string `json:"repos_url"`
	EventsURL         string `json:"events_url"`
	ReceivedEventsURL string `json:"received_events_url"`
	Type              string `json:"type"`
	SiteAdmin         bool   `json:"site_admin"`
	Name              string `json:"name"`
	Company           string `json:"company"`
	Blog              string `json:"blog"`
	Location          string `json:"location"`
	Bio               string `json:"bio"`
	TwitterUsername   string `json:"twitter_username"`
	PublicRepos       uint64 `json:"public_repos"`
	PublicGists       uint64 `json:"public_gists"`
	Followers         uint64 `json:"followers"`
	Following         uint64 `json:"following"`
	CreatedAt         string `json:"created_at"`
	UpdatedAt         string `json:"updated_at"`
}

// createRequest creates a single request to fetch from GitHub API using GitHub's unique
// 'Accept' header (application/vnd.github.v3+json).
func createRequest(url string) (*http.Response, error) {
	client := &http.Client{}
	req, err := http.NewRequest("GET", url, nil)
	req.Header.Set("Accept", "application/vnd.github.v3+json")
	if err != nil {
		return nil, err
	}

	res, err := client.Do(req)
	if err != nil {
		return nil, err
	}

	return res, nil
}

// findUnfollowers finds all users who does not follow you back.
// This is done by performing a search on the existing sets.
func findUnfollowers(followersSet map[string]bool, followingSet map[string]bool) map[string]bool {
	unfollowers := map[string]bool{}

	for key := range followingSet {
		if ok := followersSet[key]; !ok {
			unfollowers[key] = true
		}
	}

	return unfollowers
}

// getSocial fetches either 'followers' or 'following' data from GitHub API.
// Variable 'numberOfRequests' is divided by 100 as 100 is the maximum number of data
// in a single page.
func getSocial(username string, total uint64, subject string) ([]Social, error) {
	social := []Social{}

	if subject != "followers" && subject != "following" {
		return nil, errors.New("social: subject has to be either 'followers' or 'following'")
	}

	numberOfRequests := math.Ceil(float64(total) / 100)

	for i := 1; i <= int(numberOfRequests); i++ {
		currentSocial := []Social{}

		url := fmt.Sprintf("https://api.github.com/users/%s/%s?per_page=100&page=%d", username, subject, i)
		res, err := createRequest(url)
		if err != nil {
			return nil, err
		}
		defer res.Body.Close()

		err = json.NewDecoder(res.Body).Decode(&currentSocial)
		if err != nil {
			return nil, err
		}

		social = append(social, currentSocial...)
	}

	return social, nil
}

// getUser fetches data of a single user from GitHub API.
func getUser(username string) (*User, error) {
	user := &User{}

	url := fmt.Sprintf("https://api.github.com/users/%s", username)
	res, err := createRequest(url)
	if err != nil {
		return nil, err
	}
	defer res.Body.Close()

	if res.StatusCode == 404 {
		return nil, errors.New("getUser: failed to find a GitHub user with that username")
	}

	err = json.NewDecoder(res.Body).Decode(user)
	if err != nil {
		return nil, err
	}

	return user, nil
}

// printSet prints all of a set's contents with a unique message.
func printSet(message string, set map[string]bool) {
	counter := 1

	fmt.Println(message)
	for key := range set {
		fmt.Printf("%d. %s\n", counter, key)
		counter++
	}

	fmt.Printf("\n\n")
}

// socialToSet transforms a social array into a set data structure.
func socialToSet(social []Social) map[string]bool {
	set := map[string]bool{}

	for _, user := range social {
		set[user.Login] = true
	}

	return set
}

// Driver code that runs the whole program. If you want to fill your username,
// you can use 'export GITHUB_USERNAME=YOUR_GITHUB_USERNAME' before running this script,
// or by editing the 'username' variable manually.
func main() {
	username := strings.TrimSpace(os.Getenv("GITHUB_USERNAME"))
	if username == "" {
		log.Fatal(errors.New("main: variable 'username' is blank, it has to defined beforehand"))
	}

	user, err := getUser(username)
	if err != nil {
		log.Fatal(err.Error())
	}

	followers, err := getSocial(username, user.Followers, "followers")
	if err != nil {
		log.Fatal(err.Error())
	}

	following, err := getSocial(username, user.Following, "following")
	if err != nil {
		log.Fatal(err.Error())
	}

	followersSet := socialToSet(followers)
	printSet("Followers:", followersSet)

	followingSet := socialToSet(following)
	printSet("Following:", followingSet)

	unfollowers := findUnfollowers(followersSet, followingSet)
	printSet("Unfollowers:", unfollowers)

	fmt.Println("GitHub Unfollowers has finished running.")
}