feat(sdk): add AccessToken accessor to SDK

sdk/access_token_test.go

@@ -0,0 +1,73 @@
+package sdk
+
+import (
+	"context"
+	"net/http"
+	"testing"
+
+	"github.com/lestrrat-go/jwx/v2/jwk"
+	"github.com/opentdf/platform/sdk/auth"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAccessToken_ReturnsTokenFromSource(t *testing.T) {
+	s := &SDK{tokenSource: FakeAccessTokenSource{accessToken: "test-token"}}
+
+	tok, err := s.Auth().AccessToken(context.Background())
+	require.NoError(t, err)
+	assert.Equal(t, auth.AccessToken("test-token"), tok)
+}
+
+func TestAccessToken_NoTokenSource(t *testing.T) {
+	s := &SDK{}
+
+	tok, err := s.Auth().AccessToken(context.Background())
+	require.ErrorIs(t, err, ErrNoAccessTokenSource)
+	assert.Empty(t, tok)
+}
+
+func TestAccessToken_EmptyToken(t *testing.T) {
+	s := &SDK{tokenSource: FakeAccessTokenSource{accessToken: ""}}
+
+	tok, err := s.Auth().AccessToken(context.Background())
+	require.ErrorIs(t, err, ErrAccessTokenInvalid)
+	assert.Empty(t, tok)
+}
+
+type recordCtxKey struct{}
+
+// recordingTokenSource captures what AccessToken forwards to it so tests can assert
+// the context and HTTP client are passed through. It records a context value rather
+// than the context itself (avoiding a context.Context struct field) and the client
+// pointer for identity comparison.
+type recordingTokenSource struct {
+	token       string
+	gotCtxValue any
+	gotClient   *http.Client
+}
+
+func (r *recordingTokenSource) AccessToken(ctx context.Context, client *http.Client) (auth.AccessToken, error) {
+	r.gotCtxValue = ctx.Value(recordCtxKey{})
+	r.gotClient = client
+	return auth.AccessToken(r.token), nil
+}
+
+func (r *recordingTokenSource) MakeToken(func(jwk.Key) ([]byte, error)) ([]byte, error) {
+	return nil, nil
+}
+
+func TestAccessToken_ForwardsContextAndClient(t *testing.T) {
+	ctx := context.WithValue(context.Background(), recordCtxKey{}, "value")
+	client := &http.Client{}
+
+	rec := &recordingTokenSource{token: "test-token"}
+	s := &SDK{tokenSource: rec}
+	s.httpClient = client
+
+	tok, err := s.Auth().AccessToken(ctx)
+	require.NoError(t, err)
+	assert.Equal(t, auth.AccessToken("test-token"), tok)
+	assert.Equal(t, "value", rec.gotCtxValue, "context should be forwarded unchanged")
+	assert.Same(t, client, rec.gotClient, "http client should be forwarded unchanged")
+}

sdk/auth_client.go

@@ -0,0 +1,34 @@
+package sdk
+
+import (
+	"context"
+
+	"github.com/opentdf/platform/sdk/auth"
+)
+
+// Auth returns an AuthClient for authentication-related operations.
+func (s *SDK) Auth() *AuthClient {
+	return &AuthClient{sdk: s}
+}
+
+// AuthClient groups authentication operations for the SDK.
+type AuthClient struct {
+	sdk *SDK
+}
+
+// AccessToken returns a valid access token for the SDK's configured credentials.
+// It returns ErrNoAccessTokenSource if the SDK was created without credentials, and
+// ErrAccessTokenInvalid if the token source returns an empty token.
+func (a *AuthClient) AccessToken(ctx context.Context) (auth.AccessToken, error) {
+	if a.sdk.tokenSource == nil {
+		return "", ErrNoAccessTokenSource
+	}
+	token, err := a.sdk.tokenSource.AccessToken(ctx, a.sdk.httpClient)
+	if err != nil {
+		return "", err
+	}
+	if token == "" {
+		return "", ErrAccessTokenInvalid
+	}
+	return token, nil
+}

sdk/sdk.go

@@ -45,6 +45,7 @@ const (
 	ErrPlatformTokenEndpointNotFound = Error("token_endpoint not found in well-known idp configuration")
 	ErrPlatformEndpointNotFound      = Error("platform_endpoint not found in well-known configuration")
 	ErrAccessTokenInvalid            = Error("access token is invalid")
+	ErrNoAccessTokenSource           = Error("no access token source configured; SDK was created without credentials")
 	ErrWellKnowConfigEmpty           = Error("well-known configuration is empty")
 	ErrAttributeNotFound             = Error("attribute not found")
 )