Add function to fetch and renew token

.gitignore

@@ -0,0 +1,2 @@
+say-it-backend
+token.json

main.go

@@ -4,12 +4,14 @@ import (
 	"io/ioutil"
 	"net/http"
 	"os"
+	"time"
 
 	"net/url"
 
 	"encoding/json"
 
 	log "github.com/Sirupsen/logrus"
+	"github.com/davecgh/go-spew/spew"
 	"gopkg.in/gin-gonic/gin.v1"
 )
 
@@ -17,6 +19,13 @@ type Token struct {
 	AccessToken  string `json:"access_token"`
 	ExpiresIn    int    `json:"expires_in"`
 	RefreshToken string `json:"refresh_token"`
+	BaseTime     time.Time
+	ExpiresTime  time.Time
+}
+
+type ViewToken struct {
+	Token       string
+	ExpiresTime int64
 }
 
 var (
@@ -26,13 +35,17 @@ var (
 )
 
 func init() {
-	token = fetchToken()
+	loadToken()
 	clientId = os.Getenv("CLIENT_ID")
 	clientSecret = os.Getenv("CLIENT_SECRET")
 	if clientId == "" || clientSecret == "" {
 		log.Fatal("Please set environment variable CLIENT_ID and CLIENT_SECRET")
 	}
-	fetchToken()
+	if shouldFetchToken() {
+		fetchToken()
+	}
+
+	spew.Dump(token)
 }
 
 func main() {
@@ -47,28 +60,68 @@ func landing(c *gin.Context) {
 }
 
 func fetchTokenHandler(c *gin.Context) {
-
+	if time.Now().After(token.ExpiresTime) {
+		log.Info("Token expires, try to refresh one.")
+		// fetchToken()
+	}
+	if token != nil {
+		c.JSON(200, ViewToken{Token: token.AccessToken, ExpiresTime: token.ExpiresTime.Unix()})
+		return
+	}
+	c.JSON(404, gin.H{"message": "No Available Token, please concat the Admin: wahyd4@gmail.com. Thanks!"})
 }
 
-func fetchToken() *Token {
-	params := url.Values{"grant_type": {"client_credentials"}, "client_id": {clientId}, "client_secret": {clientSecret}}
+func fetchToken() {
+	log.Info("Start fetching token")
+	params := url.Values{}
+	params.Add("grant_type", "client_credentials")
+	params.Add("client_id", clientId)
+	params.Add("client_secret", clientSecret)
+
 	resp, err := http.PostForm("https://openapi.baidu.com/oauth/2.0/token", params)
 	if err != nil {
 		log.Errorln("Fetch Baidu access token failed" + err.Error())
 	}
 
-	// defer resp.Body.Close()
+	defer resp.Body.Close()
 	body, _ := ioutil.ReadAll(resp.Body)
 
 	if resp.Status != "200 OK" {
 		log.Errorln("The response of fetch Baidu access token not success: " + string(body))
-		// return nil
+		return
 	}
 
 	var t Token
 	err = json.Unmarshal(body, &t)
 	if err != nil {
-		log.Warnln("Unmarshal json failed: " + err.Error())
+		log.Warn("Unmarshal json failed: " + err.Error())
 	}
-	return &t
+	t.BaseTime = time.Now()
+	t.ExpiresTime = token.BaseTime.Add(time.Second * time.Duration(token.ExpiresIn))
+
+	writeToFile(&t)
+	token = &t
+}
+
+func writeToFile(token *Token) {
+	log.Info("Write updated token to file")
+	tokenJSON, _ := json.Marshal(token)
+	ioutil.WriteFile("./token.json", tokenJSON, 0644)
+}
+
+func loadToken() {
+	log.Info("Loading token from local file")
+	tokenString, err := ioutil.ReadFile("./token.json")
+	if err != nil {
+		log.Warn("Load json file failed, maybe there " + err.Error())
+		return
+	}
+
+	var t Token
+	json.Unmarshal(tokenString, &t)
+	token = &t
+}
+
+func shouldFetchToken() bool {
+	return token == nil || token.AccessToken == "" || time.Now().After(token.ExpiresTime)
 }