assign reviewer for github

roulette.go

package main

import (
	"encoding/json"
	"io"
	"log"
	"math/rand"
	"net/http"
	"os"
	"strings"
)

var (
	githubToken = os.Getenv("GITHUB_TOKEN")
	githubUsers = strings.Split(os.Getenv("GITHUB_REVIEWERS"), ",")
)

// assign reviewer
func assign(url string, user string) error {
	assignBody := "{\"assignee\":\"" + user + "\"}"

	// update state
	r, _ := http.NewRequest("PATCH", url, strings.NewReader(assignBody))
	r.Header.Add("Authorization", "token "+githubToken)
	r.Header.Add("Content-Type", "application/json")
	client := &http.Client{}
	resp, err := client.Do(r)
	defer resp.Body.Close()
	if err != nil {
		log.Print(err)
		return err
	}
	return nil
}

func comment(url string, user string) error {
	body := "{\"body\":\"@" + user + "please review\"}"
	r, _ := http.NewRequest("POST", url, strings.NewReader(body))
	r.Header.Add("Authorization", "token "+githubToken)
	r.Header.Add("Content-Type", "application/json")
	client := &http.Client{}
	resp, err := client.Do(r)
	defer resp.Body.Close()
	if err != nil {
		log.Print(err)
		return err
	}
	return nil
}

func Hook(w http.ResponseWriter, req *http.Request) {
	err := req.ParseForm()
	if err != nil {
		log.Print(err)
		// TODO: 500 error
		return
	}

	v := req.FormValue("payload")
	var m map[string]interface{}
	err = json.Unmarshal([]byte(v), &m)
	if err != nil {
		log.Print(err)
		// TODO: 500 error
		return
	}

	if m["action"] != "opened" {
		return
	}

	links := m["pull_request"].(map[string]interface{})["_links"].(map[string]interface{})
	assignUrl := links["issue"].(map[string]interface{})["href"].(string)
	commentUrl := links["comments"].(map[string]interface{})["href"].(string)
	reviewer := githubUsers[rand.Intn(len(githubUsers))]
	assign(assignUrl, reviewer)
	comment(commentUrl, reviewer)
}

func ping(w http.ResponseWriter, req *http.Request) {
	io.WriteString(w, "pong\n")
}

func main() {
	log.Printf("reviewer candidates are %v", githubUsers)
	port := os.Getenv("PORT")
	if len(port) == 0 {
		port = "8000"
	}
	http.HandleFunc("/", Hook)
	http.HandleFunc("/ping", ping)
	log.Printf("start server. port: %v", port)
	err := http.ListenAndServe(":"+port, nil)

	if err != nil {
		log.Fatal("ListenAndServe: ", err)
	}
}