From e83092a0031874aac3dc74b3b74e60953310258c Mon Sep 17 00:00:00 2001
From: Florian Forster <octo@google.com>
Date: Tue, 10 Nov 2020 14:12:39 +0100
Subject: [PATCH] Sheets API: Simplify quickstart code by using
 option.WithCredentialsFile().

---
 sheets/quickstart/quickstart.go | 87 +++++----------------------------
 1 file changed, 13 insertions(+), 74 deletions(-)

diff --git a/sheets/quickstart/quickstart.go b/sheets/quickstart/quickstart.go
index 59d161e..7a7f24f 100644
--- a/sheets/quickstart/quickstart.go
+++ b/sheets/quickstart/quickstart.go
@@ -18,88 +18,27 @@
 package main
 
 import (
-	"encoding/json"
+	"context"
 	"fmt"
-	"io/ioutil"
 	"log"
-	"net/http"
-	"os"
 
-	"golang.org/x/net/context"
-	"golang.org/x/oauth2"
-	"golang.org/x/oauth2/google"
+	"google.golang.org/api/option"
 	"google.golang.org/api/sheets/v4"
 )
 
-// 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 main() {
-	b, err := ioutil.ReadFile("credentials.json")
-	if err != nil {
-		log.Fatalf("Unable to read client secret file: %v", err)
-	}
+	ctx := context.Background()
 
-	// If modifying these scopes, delete your previously saved token.json.
-	config, err := google.ConfigFromJSON(b, "https://www.googleapis.com/auth/spreadsheets.readonly")
-	if err != nil {
-		log.Fatalf("Unable to parse client secret file to config: %v", err)
-	}
-	client := getClient(config)
+	srv, err := sheets.NewService(ctx,
+		// Authenticate with a service account or refresh token JSON credentials file.
+		// Remove this option to authenticate via Application Default Credentials.
+		option.WithCredentialsFile("credentials.json"),
 
-	srv, err := sheets.New(client)
+		// Be default, the sheets package requests all scopes that it could
+		// potentially need. This passes the read-only scope explicitly to
+		// limit the requested scopes to what is actually needed.
+		option.WithScopes(sheets.SpreadsheetsReadonlyScope),
+	)
 	if err != nil {
 		log.Fatalf("Unable to retrieve Sheets client: %v", err)
 	}
@@ -108,7 +47,7 @@ func main() {
 	// https://docs.google.com/spreadsheets/d/1BxiMVs0XRA5nFMdKvBdBZjgmUUqptlbs74OgvE2upms/edit
 	spreadsheetId := "1BxiMVs0XRA5nFMdKvBdBZjgmUUqptlbs74OgvE2upms"
 	readRange := "Class Data!A2:E"
-	resp, err := srv.Spreadsheets.Values.Get(spreadsheetId, readRange).Do()
+	resp, err := srv.Spreadsheets.Values.Get(spreadsheetId, readRange).Context(ctx).Do()
 	if err != nil {
 		log.Fatalf("Unable to retrieve data from sheet: %v", err)
 	}