feat(security): implement ChainAuthenticator for sequential authentication

pkg/security/chain.go

@@ -0,0 +1,41 @@
+package security
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+)
+
+// ChainAuthenticator tries each authenticator in order, returning the first success.
+// Login and Logout are delegated to the primary authenticator.
+type ChainAuthenticator struct {
+	authenticators []Authenticator
+}
+
+// NewChainAuthenticator creates a ChainAuthenticator from the given authenticators.
+// At least one authenticator is required; the first is treated as primary for Login/Logout.
+func NewChainAuthenticator(primary Authenticator, rest ...Authenticator) *ChainAuthenticator {
+	return &ChainAuthenticator{
+		authenticators: append([]Authenticator{primary}, rest...),
+	}
+}
+
+func (c *ChainAuthenticator) Authenticate(r *http.Request) (*UserContext, error) {
+	var lastErr error
+	for _, a := range c.authenticators {
+		if uc, err := a.Authenticate(r); err == nil {
+			return uc, nil
+		} else {
+			lastErr = err
+		}
+	}
+	return nil, fmt.Errorf("all authenticators failed; last error: %w", lastErr)
+}
+
+func (c *ChainAuthenticator) Login(ctx context.Context, req LoginRequest) (*LoginResponse, error) {
+	return c.authenticators[0].Login(ctx, req)
+}
+
+func (c *ChainAuthenticator) Logout(ctx context.Context, req LogoutRequest) error {
+	return c.authenticators[0].Logout(ctx, req)
+}

pkg/security/chain_test.go

@@ -0,0 +1,117 @@
+package security
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+// stubAuthenticator is a configurable Authenticator for testing.
+type stubAuthenticator struct {
+	userCtx *UserContext
+	err     error
+}
+
+func (s *stubAuthenticator) Authenticate(_ *http.Request) (*UserContext, error) {
+	return s.userCtx, s.err
+}
+
+func (s *stubAuthenticator) Login(_ context.Context, _ LoginRequest) (*LoginResponse, error) {
+	if s.err != nil {
+		return nil, s.err
+	}
+	return &LoginResponse{Token: "tok"}, nil
+}
+
+func (s *stubAuthenticator) Logout(_ context.Context, _ LogoutRequest) error {
+	return s.err
+}
+
+func TestChainAuthenticator_Authenticate(t *testing.T) {
+	successCtx := &UserContext{UserID: 42, UserName: "alice"}
+	failStub := &stubAuthenticator{err: fmt.Errorf("no token")}
+	okStub := &stubAuthenticator{userCtx: successCtx}
+
+	t.Run("primary succeeds", func(t *testing.T) {
+		chain := NewChainAuthenticator(okStub, failStub)
+		req := httptest.NewRequest("GET", "/", nil)
+
+		uc, err := chain.Authenticate(req)
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if uc.UserID != 42 {
+			t.Errorf("expected UserID 42, got %d", uc.UserID)
+		}
+	})
+
+	t.Run("primary fails, secondary succeeds", func(t *testing.T) {
+		chain := NewChainAuthenticator(failStub, okStub)
+		req := httptest.NewRequest("GET", "/", nil)
+
+		uc, err := chain.Authenticate(req)
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if uc.UserID != 42 {
+			t.Errorf("expected UserID 42, got %d", uc.UserID)
+		}
+	})
+
+	t.Run("all fail", func(t *testing.T) {
+		chain := NewChainAuthenticator(failStub, failStub)
+		req := httptest.NewRequest("GET", "/", nil)
+
+		_, err := chain.Authenticate(req)
+		if err == nil {
+			t.Fatal("expected error when all authenticators fail")
+		}
+	})
+
+	t.Run("three in chain, first two fail", func(t *testing.T) {
+		chain := NewChainAuthenticator(failStub, failStub, okStub)
+		req := httptest.NewRequest("GET", "/", nil)
+
+		uc, err := chain.Authenticate(req)
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if uc.UserName != "alice" {
+			t.Errorf("expected UserName alice, got %s", uc.UserName)
+		}
+	})
+}
+
+func TestChainAuthenticator_LoginLogout(t *testing.T) {
+	primary := &stubAuthenticator{userCtx: &UserContext{UserID: 1}}
+	secondary := &stubAuthenticator{userCtx: &UserContext{UserID: 2}}
+	chain := NewChainAuthenticator(primary, secondary)
+	ctx := context.Background()
+
+	t.Run("login delegates to primary", func(t *testing.T) {
+		resp, err := chain.Login(ctx, LoginRequest{Username: "u", Password: "p"})
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if resp.Token != "tok" {
+			t.Errorf("expected token from primary, got %s", resp.Token)
+		}
+	})
+
+	t.Run("logout delegates to primary", func(t *testing.T) {
+		if err := chain.Logout(ctx, LogoutRequest{}); err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+	})
+
+	t.Run("login error from primary is returned", func(t *testing.T) {
+		failPrimary := &stubAuthenticator{err: fmt.Errorf("db down")}
+		chain2 := NewChainAuthenticator(failPrimary, secondary)
+		_, err := chain2.Login(ctx, LoginRequest{})
+		if err == nil {
+			t.Fatal("expected error from primary login failure")
+		}
+	})
+}