full script for Slack and Garmin integration

main.go

package main

import (
	"encoding/json"
	"fmt"
	"github.com/slack-go/slack"
	"golang.org/x/net/context"
	"golang.org/x/oauth2"
	"golang.org/x/oauth2/google"
	"google.golang.org/api/gmail/v1"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"time"
)

const user = "me"
const SlackAccessToken = ""

// Retrieve a token, saves the token, then returns the generated client.
func getClient(config *oauth2.Config) *http.Client {
	// The file token.json stores the user's access and refresh tokens, and is
	// created automatically when the authorization flow completes for the first
	// time.
	tokFile := "token.json"
	tok, err := tokenFromFile(tokFile)
	if err != nil {
		tok = getTokenFromWeb(config)
		saveToken(tokFile, tok)
	}
	return config.Client(context.Background(), tok)
}

// Request a token from the web, then returns the retrieved token.
func getTokenFromWeb(config *oauth2.Config) *oauth2.Token {
	authURL := config.AuthCodeURL("state-token", oauth2.AccessTypeOffline)
	fmt.Printf("Go to the following link in your browser then type the "+
		"authorization code: \n%v\n", authURL)

	var authCode string
	if _, err := fmt.Scan(&authCode); err != nil {
		log.Fatalf("Unable to read authorization code: %v", err)
	}

	tok, err := config.Exchange(context.TODO(), authCode)
	if err != nil {
		log.Fatalf("Unable to retrieve token from web: %v", err)
	}
	return tok
}

// Retrieves a token from a local file.
func tokenFromFile(file string) (*oauth2.Token, error) {
	f, err := os.Open(file)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	tok := &oauth2.Token{}
	err = json.NewDecoder(f).Decode(tok)
	return tok, err
}

// Saves a token to a file path.
func saveToken(path string, token *oauth2.Token) {
	fmt.Printf("Saving credential file to: %s\n", path)
	f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
	if err != nil {
		log.Fatalf("Unable to cache oauth token: %v", err)
	}
	defer f.Close()
	json.NewEncoder(f).Encode(token)
}

func getLabels(srv *gmail.Service) {
	r, err := srv.Users.Labels.List(user).Do()
	if err != nil {
		log.Fatalf("Unable to retrieve labels: %v", err)
	}
	if len(r.Labels) == 0 {
		fmt.Println("No labels found.")
		return
	}
	fmt.Println("Labels:")
	for _, l := range r.Labels {
		fmt.Printf("- %s\n", l.Name)
	}
}

func getLastMessageId(srv *gmail.Service) string {
	r, err := srv.Users.Messages.List(user).MaxResults(100).Q("to:testuser+garminlivetrack@gmail.com is:unread").Do()
	if err != nil {
		log.Fatalf("Unable to retrieve messages: %v", err)
	}
	if len(r.Messages) == 0 {
		fmt.Println("No messages found.")
		os.Exit(1)
	}
	return r.Messages[len(r.Messages)-1].Id
}

func getLastMessageData(srv *gmail.Service, lastMessageId string) string {
	r, err := srv.Users.Messages.Get(user, lastMessageId).Do()
	if err != nil {
		log.Fatalf("Unable to retrieve message: %v", err)
	}
	if len(r.Id) == 0 {
		fmt.Println("No message data found.")
		return ""
	}
	return r.Payload.Body.Data
}

func markAsRead(srv *gmail.Service, lastMessageId string) {
	var labels []string
	labels = append(labels, "UNREAD")
	_, err := srv.Users.Messages.Modify(user, lastMessageId, &gmail.ModifyMessageRequest{RemoveLabelIds: labels}).Do()
	if err != nil {
		log.Fatalf("Unable to modify message: %v", err)
	}
}

func setSlackStatus() {
	api := slack.New(SlackAccessToken, slack.OptionDebug(false))
	expirationTime := time.Now().Add(time.Hour * time.Duration(3)).Unix()
	err := api.SetUserCustomStatus("Gone Cycling", "🚴🏻‍♂️", expirationTime)
	if err != nil {
		log.Fatalf("Unable to set status : %v", err)
	}
	err = api.SetUserPresence("away")
	if err != nil {
		log.Fatalf("Unable to set presence : %v", err)
	}
}

func main() {
	b, err := ioutil.ReadFile("credentials.json")
	if err != nil {
		log.Fatalf("Unable to read client secret file: %v", err)
	}

	// If modifying these scopes, delete your previously saved token.json.
	config, err := google.ConfigFromJSON(b, gmail.GmailModifyScope)
	if err != nil {
		log.Fatalf("Unable to parse client secret file to config: %v", err)
	}
	client := getClient(config)

	srv, err := gmail.New(client)
	if err != nil {
		log.Fatalf("Unable to retrieve Gmail client: %v", err)
	}

	lastMessageId := getLastMessageId(srv)
	base64Data := getLastMessageData(srv, lastMessageId)

	fmt.Println("Message:")
	fmt.Println(base64Data)
	setSlackStatus()
	markAsRead(srv, lastMessageId)
}