1 files changed, 88 insertions, 6 deletions

diff --git a/internal/oauth/token.go b/internal/oauth/token.go
index 31c2c74..855677c 100644
--- a/internal/oauth/token.go
+++ b/internal/oauth/token.go
@@ -1,6 +1,12 @@
 package oauth
 
-import "time"
+import (
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/go-errors/errors"
+)
 
 // TokenResponse defines the OAuth response from the server that includes the tokens.
 type TokenResponse struct {
@@ -17,8 +23,8 @@ type TokenResponse struct {
 	Expires int64 `json:"expires_in"`
 }
 
-// Token is a structure that contains our access and refresh tokens and a timestamp when they expire.
-type Token struct {
+// token is a structure that contains our access and refresh tokens and a timestamp when they expire.
+type token struct {
 	// Access is the access token returned by the server
 	access string
 
@@ -27,10 +33,86 @@ type Token struct {
 
 	// ExpiredTimestamp is the Expires field but converted to a Go timestamp
 	expiredTimestamp time.Time
+
+	// Refresher is the function that refreshes the token
+	Refresher func(string) (*TokenResponse, time.Time, error)
+}
+
+// tokenLock is a wrapper around token that protects it with a lock
+type tokenLock struct {
+	// Protects t
+	mu sync.Mutex
+
+	// The token fields protected by the lock
+	t *token
+}
+
+// Access gets the OAuth access token used for contacting the server API
+// It returns the access token as a string, possibly obtained fresh using the refresher
+// If the token cannot be obtained, an error is returned and the token is an empty string.
+func (l *tokenLock) Access() (string, error) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	// The tokens are not expired yet
+	// So they should be valid, re-login not neede
+	if !l.expired() {
+		return l.t.access, nil
+	}
+
+	// Check if refresh is even possible by doing a simple check if the refresh token is empty
+	// This is not needed but reduces API calls to the server
+	if l.t.refresh == "" {
+		return "", errors.Wrap(&TokensInvalidError{Cause: "no refresh token is present"}, 0)
+	}
+
+	// Otherwise refresh and then later return the access token if we are successful
+	tr, s, err := l.t.Refresher(l.t.refresh)
+	if err != nil {
+		// We have failed to ensure the tokens due to refresh not working
+		return "", errors.Wrap(
+			&TokensInvalidError{Cause: fmt.Sprintf("tokens failed refresh with error: %v", err)}, 0)
+	}
+	if tr == nil {
+		return "", errors.New("No token response after refreshing")
+	}
+	l.updateInternal(*tr, s)
+	return l.t.access, nil
+}
+
+// Clear completely clears the token structure
+// This is useful for forcing re-authorization
+func (l *tokenLock) Clear() {
+	l.mu.Lock()
+	l.t = &token{}
+	l.mu.Unlock()
+}
+
+// updateInternal updates the structure using the response without locking
+func (l *tokenLock) updateInternal(r TokenResponse, s time.Time) {
+	l.t.access = r.Access
+	l.t.refresh = r.Refresh
+	l.t.expiredTimestamp = s.Add(time.Second * time.Duration(r.Expires))
+}
+
+// Update updates the structure usign the response and locks
+func (l *tokenLock) Update(r TokenResponse, s time.Time) {
+	l.mu.Lock()
+	l.updateInternal(r, s)
+	l.mu.Unlock()
+}
+
+// SetExpired overrides the timestamp to the current time
+// This marks the tokens as expired
+func (l *tokenLock) SetExpired() {
+	l.mu.Lock()
+	l.t.expiredTimestamp = time.Now()
+	l.mu.Unlock()
 }
 
-// Expired checks if the access token is expired.
-func (tokens *Token) Expired() bool {
+// expired checks if the access token is expired.
+// This is only called internally and thus does not lock
+func (l *tokenLock) expired() bool {
 	now := time.Now()
-	return !now.Before(tokens.expiredTimestamp)
+	return !now.Before(l.t.expiredTimestamp)
 }