refactor authentication

authentication.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os"
+	"encoding/json"
+	"net/http"
+	"path/filepath"
+
+	"golang.org/x/oauth2"
+)
+
+func getClient(config *oauth2.Config) *http.Client {
+	token_file := filepath.Join(CREDENTIALS_DIR, TOKEN_FILE)
+	token, err := tokenFromFile(token_file)
+	if err != nil {
+		token = getTokenFromWeb(config)
+		saveToken(token_file, token)
+	}
+	return config.Client(context.Background(), token)
+}
+
+func getTokenFromWeb(config *oauth2.Config) *oauth2.Token {
+	auth_url := config.AuthCodeURL("state-token", oauth2.AccessTypeOffline)
+	fmt.Printf("Go to the following link in your browser, then type the " +
+		"authorization code: \n%v\n", auth_url)
+	
+	var auth_code string
+	if _, err := fmt.Scan(&auth_code) ; err != nil {
+		log.Fatalf("Unable to read authorization code: %v", err)
+	}
+
+	token, err := config.Exchange(context.TODO(), auth_code)
+	if err != nil {
+		log.Fatalf("Unable to retrieve token from web: %v", err)
+	}
+	return token
+}
+
+func tokenFromFile(file string) (*oauth2.Token, error) {
+	f, err := os.Open(file)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	token := &oauth2.Token{}
+	err = json.NewDecoder(f).Decode(token)
+	return token, err
+}
+
+func saveToken(path string, token *oauth2.Token) {
+	fmt.Printf("Saving credential file to: %s\n", path)
+	file, 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 file.Close()
+	json.NewEncoder(file).Encode(token)
+}

main.go

@@ -2,72 +2,24 @@ package main
 
 import (
 	"context"
-	"encoding/json"
 	"fmt"
 	"log"
-	"net/http"
 	"os"
+	"path/filepath"
 
-	"golang.org/x/oauth2"
 	"golang.org/x/oauth2/google"
 	"google.golang.org/api/gmail/v1"
 	"google.golang.org/api/option"
 )
 
-const TOKEN_FILE string = "creds/token.json"
-const CREDENTIALS_FILE string = "creds/credentials.json"
-
-func getClient(config *oauth2.Config) *http.Client {
-	token_file := TOKEN_FILE
-	token, err := tokenFromFile(token_file)
-	if err != nil {
-		token = getTokenFromWeb(config)
-		saveToken(token_file, token)
-	}
-	return config.Client(context.Background(), token)
-}
-
-func getTokenFromWeb(config *oauth2.Config) *oauth2.Token {
-	auth_url := config.AuthCodeURL("state-token", oauth2.AccessTypeOffline)
-	fmt.Printf("Go to the following link in your browser, then type the " +
-		"authorization code: \n%v\n", auth_url)
-	
-	var auth_code string
-	if _, err := fmt.Scan(&auth_code) ; err != nil {
-		log.Fatalf("Unable to read authorization code: %v", err)
-	}
-
-	token, err := config.Exchange(context.TODO(), auth_code)
-	if err != nil {
-		log.Fatalf("Unable to retrieve token from web: %v", err)
-	}
-	return token
-}
-
-func tokenFromFile(file string) (*oauth2.Token, error) {
-	f, err := os.Open(file)
-	if err != nil {
-		return nil, err
-	}
-	defer f.Close()
-	token := &oauth2.Token{}
-	err = json.NewDecoder(f).Decode(token)
-	return token, err
-}
-
-func saveToken(path string, token *oauth2.Token) {
-	fmt.Printf("Saving credential file to: %s\n", path)
-	file, 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 file.Close()
-	json.NewEncoder(file).Encode(token)
-}
+const CREDENTIALS_DIR = "creds"
+const TOKEN_FILE = "token.json"
+const CREDENTIALS_FILE = "credentials.json"
 
 func main() {
 	ctx := context.Background()
-	creds_b, err := os.ReadFile(CREDENTIALS_FILE)
+	creds_file := filepath.Join(CREDENTIALS_DIR, CREDENTIALS_FILE)
+	creds_b, err := os.ReadFile(creds_file)
 	if err != nil {
 		log.Fatalf("Unable to read client secret file: %v", err)
 	}