oauth can refresh

email.go

@@ -1,18 +1,22 @@
 package contact
 
 import (
+	"bytes"
 	"context"
 	"crypto/sha256"
 	"crypto/tls"
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
+	"io"
 	"log"
+	"net/http"
 	"net/mail"
 	"net/smtp"
 	"net/url"
 	"os"
 	"strings"
+	"time"
 
 	"github.com/bytbox/go-pop3"
 	"github.com/emersion/go-imap"
@@ -97,12 +101,44 @@ func (e *Emailer) oauthThenReadIMAP() (chan *mail.Message, error) {
 		os.WriteFile(e.OAuth+".token", tokenFileJSON, os.ModePerm)
 		log.Printf("%s", tokenFileJSON)
 	}
-	token, _ := os.ReadFile(e.OAuth + ".token")
 	var tokenStruct struct {
-		AccessToken string `json:"access_token"`
+		AccessToken  string    `json:"access_token"`
+		RefreshToken string    `json:"refresh_token"`
+		Expiry       time.Time `json:"expiry"`
+		ExpiresIn    int       `json:"expires_in"`
 	}
+	token, _ := os.ReadFile(e.OAuth + ".token")
 	json.Unmarshal(token, &tokenStruct)
-	log.Println(e.From, tokenStruct.AccessToken)
+	if time.Until(tokenStruct.Expiry) < time.Minute*5 {
+		var appStruct struct {
+			Installed struct {
+				ClientID     string `json:"client_id"`
+				ClientSecret string `json:"client_secret"`
+				GrantType    string `json:"grant_type"`
+				RefreshToken string `json:"refresh_token"`
+			} `json:"installed"`
+		}
+		json.Unmarshal([]byte(configJSON), &appStruct)
+		appStruct.Installed.GrantType = "refresh_token"
+		appStruct.Installed.RefreshToken = tokenStruct.RefreshToken
+		b, _ := json.Marshal(appStruct.Installed)
+		resp, err := http.Post(`https://oauth2.googleapis.com/token`, `application/json`, bytes.NewReader(b))
+		if err != nil {
+			return nil, err
+		}
+		defer resp.Body.Close()
+		b, _ = io.ReadAll(resp.Body)
+		if resp.StatusCode != http.StatusOK {
+			return nil, fmt.Errorf("(%d) %s", resp.StatusCode, b)
+		}
+		tokenStruct.Expiry = time.Time{}
+		json.Unmarshal(b, &tokenStruct)
+		tokenStruct.Expiry = time.Now().Add(time.Duration(tokenStruct.ExpiresIn) * time.Second)
+		tokenStruct.RefreshToken = appStruct.Installed.RefreshToken
+		b, _ = json.Marshal(tokenStruct)
+		os.WriteFile(e.OAuth+".token", b, os.ModePerm)
+	}
+	log.Println("OAUTH", e.From, time.Until(tokenStruct.Expiry), tokenStruct.AccessToken)
 	return e.readIMAP(e.From, tokenStruct.AccessToken)
 }