oauthdevice: add RefreshToken field and Refresh method

Author: burmudar

internal/oauthdevice/device_flow.go

@@ -68,6 +68,7 @@ type Client interface {
 	Discover(ctx context.Context, endpoint string) (*OIDCConfiguration, error)
 	Start(ctx context.Context, endpoint string, scopes []string) (*DeviceAuthResponse, error)
 	Poll(ctx context.Context, endpoint, deviceCode string, interval time.Duration, expiresIn int) (*TokenResponse, error)
+	Refresh(ctx context.Context, endpoint, refreshToken string) (*TokenResponse, error)
 }
 
 type httpClient struct {
@@ -307,3 +308,55 @@ func (c *httpClient) pollOnce(ctx context.Context, tokenEndpoint, deviceCode str
 
 	return &tokenResp, nil
 }
+
+// Refresh exchanges a refresh token for a new access token.
+func (c *httpClient) Refresh(ctx context.Context, endpoint, refreshToken string) (*TokenResponse, error) {
+	endpoint = strings.TrimRight(endpoint, "/")
+
+	config, err := c.Discover(ctx, endpoint)
+	if err != nil {
+		return nil, errors.Wrap(err, "OIDC discovery failed")
+	}
+
+	if config.TokenEndpoint == "" {
+		return nil, errors.New("token endpoint not found in OIDC configuration")
+	}
+
+	data := url.Values{}
+	data.Set("client_id", c.clientID)
+	data.Set("grant_type", "refresh_token")
+	data.Set("refresh_token", refreshToken)
+
+	req, err := http.NewRequestWithContext(ctx, "POST", config.TokenEndpoint, strings.NewReader(data.Encode()))
+	if err != nil {
+		return nil, errors.Wrap(err, "creating refresh token request")
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Set("Accept", "application/json")
+
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return nil, errors.Wrap(err, "refresh token request failed")
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, errors.Wrap(err, "reading refresh token response")
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		var errResp ErrorResponse
+		if err := json.Unmarshal(body, &errResp); err == nil && errResp.Error != "" {
+			return nil, errors.Newf("refresh token failed: %s: %s", errResp.Error, errResp.ErrorDescription)
+		}
+		return nil, errors.Newf("refresh token failed with status %d: %s", resp.StatusCode, string(body))
+	}
+
+	var tokenResp TokenResponse
+	if err := json.Unmarshal(body, &tokenResp); err != nil {
+		return nil, errors.Wrap(err, "parsing refresh token response")
+	}
+
+	return &tokenResp, nil
+}

internal/oauthdevice/device_flow_test.go

@@ -507,3 +507,44 @@ func TestPoll_ContextCancellation(t *testing.T) {
 		t.Errorf("error = %v, want context.Canceled or wrapped context canceled error", err)
 	}
 }
+
+func TestRefresh_Success(t *testing.T) {
+	server := newTestServer(t, testServerOptions{
+		handlers: map[string]http.HandlerFunc{
+			testTokenPath: func(w http.ResponseWriter, r *http.Request) {
+				if err := r.ParseForm(); err != nil {
+					http.Error(w, "bad request", http.StatusBadRequest)
+					return
+				}
+				if got := r.FormValue("grant_type"); got != "refresh_token" {
+					t.Errorf("grant_type = %q, want %q", got, "refresh_token")
+				}
+				if got := r.FormValue("refresh_token"); got != "test-refresh-token" {
+					t.Errorf("refresh_token = %q, want %q", got, "test-refresh-token")
+				}
+
+				w.Header().Set("Content-Type", "application/json")
+				json.NewEncoder(w).Encode(TokenResponse{
+					AccessToken:  "new-access-token",
+					RefreshToken: "new-refresh-token",
+					TokenType:    "Bearer",
+					ExpiresIn:    3600,
+				})
+			},
+		},
+	})
+	defer server.Close()
+
+	client := NewClient(DefaultClientID)
+	resp, err := client.Refresh(context.Background(), server.URL, "test-refresh-token")
+	if err != nil {
+		t.Fatalf("Refresh() error = %v", err)
+	}
+
+	if resp.AccessToken != "new-access-token" {
+		t.Errorf("AccessToken = %q, want %q", resp.AccessToken, "new-access-token")
+	}
+	if resp.RefreshToken != "new-refresh-token" {
+		t.Errorf("RefreshToken = %q, want %q", resp.RefreshToken, "new-refresh-token")
+	}
+}