feat: Added simple access token caching

.gitignore

@@ -28,3 +28,4 @@
 .vscode
 .idea
 test_config.json
+.DS_Store

server/server.go

@@ -8,11 +8,14 @@ import (
 	"io"
 	"io/ioutil"
 	"log"
+	"math"
 	"mime/multipart"
 	"net/http"
 	"net/url"
+	"os"
 	"regexp"
 	"strings"
+	"time"
 )
 
 const (
@@ -40,6 +43,11 @@ type Server struct {
 	Configuration
 }
 
+type TokenCache struct {
+	AccessToken string `json:"access_token"`
+	ExpiresIn   int    `json:"expires_in"`
+}
+
 // New returns an initialized Secrets object
 func New(config Configuration) (*Server, error) {
 	if config.ServerURL == "" && config.Tenant == "" || config.ServerURL != "" && config.Tenant != "" {
@@ -252,12 +260,43 @@ func (s Server) uploadFile(secretId int, fileField SecretField) error {
 	return err
 }
 
+func (s *Server) setCacheAccessToken(value string, expiresIn int) error {
+	cache := TokenCache{}
+	cache.AccessToken = value
+	cache.ExpiresIn = (int(time.Now().Unix()) + expiresIn) - int(math.Floor(float64(expiresIn)*0.9))
+
+	data, _ := json.Marshal(cache)
+	os.Setenv("SS_AT", string(data))
+	return nil
+}
+
+func (s *Server) getCacheAccessToken() (string, bool) {
+	data, ok := os.LookupEnv("SS_AT")
+	if !ok {
+		os.Setenv("SS_AT", "")
+		return "", ok
+	}
+	cache := TokenCache{}
+	if err := json.Unmarshal([]byte(data), &cache); err != nil {
+		return "", false
+	}
+	if time.Now().Unix() < int64(cache.ExpiresIn) {
+		return cache.AccessToken, true
+	}
+	return "", false
+}
+
 // getAccessToken gets an OAuth2 Access Grant and returns the token
 // endpoint and get an accessGrant.
 func (s *Server) getAccessToken() (string, error) {
 	if s.Credentials.Token != "" {
 		return s.Credentials.Token, nil
 	}
+	accessToken, found := s.getCacheAccessToken()
+	if found {
+		return accessToken, nil
+	}
+
 	response, err := s.checkPlatformDetails()
 	if err != nil {
 		log.Print("Error while checking server details:", err)
@@ -292,6 +331,10 @@ func (s *Server) getAccessToken() (string, error) {
 			log.Print("[ERROR] parsing grant response:", err)
 			return "", err
 		}
+		if err = s.setCacheAccessToken(grant.AccessToken, grant.ExpiresIn); err != nil {
+			log.Print("[ERROR] caching access token:", err)
+			return "", err
+		}
 		return grant.AccessToken, nil
 	} else {
 		return response, nil