coder · spikecurtis · Sep 6, 2022 · Aug 29, 2022 · Sep 6, 2022
diff --git a/coderd/features.go b/coderd/features.go
@@ -2,7 +2,11 @@ package coderd
 
 import (
 	"net/http"
+	"reflect"
 
+	"golang.org/x/xerrors"
+
+	"github.com/coder/coder/coderd/audit"
 	"github.com/coder/coder/coderd/httpapi"
 	"github.com/coder/coder/codersdk"
 )
@@ -11,11 +15,10 @@ import (
 type FeaturesService interface {
 	EntitlementsAPI(w http.ResponseWriter, r *http.Request)
 
-	// TODO
-	// Get returns the implementations for feature interfaces. Parameter `s `must be a pointer to a
+	// Get returns the implementations for feature interfaces. Parameter `s` must be a pointer to a
 	// struct type containing feature interfaces as fields.  The FeatureService sets all fields to
 	// the correct implementations depending on whether the features are turned on.
-	// Get(s any) error
+	Get(s any) error
 }
 
 type featuresService struct{}
@@ -34,3 +37,57 @@ func (featuresService) EntitlementsAPI(rw http.ResponseWriter, _ *http.Request)
 		HasLicense: false,
 	})
 }
+
+// Get returns the implementations for feature interfaces. Parameter `s` must be a pointer to a
+// struct type containing feature interfaces as fields.  The AGPL featureService always returns the
+// "disabled" version of the feature interface because it doesn't include any enterprise features
+// by definition.
+func (featuresService) Get(ps any) error {
+	if reflect.TypeOf(ps).Kind() != reflect.Pointer {
+		return xerrors.New("input must be pointer to struct")
+	}
+	vs := reflect.ValueOf(ps).Elem()
+	if vs.Kind() != reflect.Struct {
+		return xerrors.New("input must be pointer to struct")
+	}
+	for i := 0; i < vs.NumField(); i++ {
+		vf := vs.Field(i)
+		tf := vf.Type()
+		if tf.Kind() != reflect.Interface {
+			return xerrors.Errorf("fields of input struct must be interfaces: %s", tf.String())
+		}
+		err := setImplementation(vf, tf)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// setImplementation finds the correct implementation for the field's type, and sets it on the
+// struct.  It returns an error if unsuccessful
+func setImplementation(vf reflect.Value, tf reflect.Type) error {
+	// when we get more than a few features it might make sense to have a data structure for finding
+	// the correct implementation that's faster than just a linear search, but for now just spin
+	// through the implementations we have.
+	vd := reflect.ValueOf(DisabledImplementations)
+	for j := 0; j < vd.NumField(); j++ {
+		vdf := vd.Field(j)
+		if vdf.Type() == tf {
+			vf.Set(vdf)
+			return nil
+		}
+	}
+	return xerrors.Errorf("unable to find implementation of interface %s", tf.String())
+}
+
+// FeatureInterfaces contains a field for each interface controlled by an enterprise feature.
+type FeatureInterfaces struct {
+	Auditor audit.Auditor
+}
+
+// DisabledImplementations includes all the implementations of turned-off features.  There are no
+// turned-on implementations in AGPL code.
+var DisabledImplementations = FeatureInterfaces{
+	Auditor: audit.NewNop(),
+}
diff --git a/coderd/features_internal_test.go b/coderd/features_internal_test.go
@@ -9,6 +9,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
+	"github.com/coder/coder/coderd/audit"
 	"github.com/coder/coder/codersdk"
 )
 
@@ -36,3 +37,64 @@ func TestEntitlements(t *testing.T) {
 		}
 	})
 }
+
+func TestFeaturesServiceGet(t *testing.T) {
+	t.Parallel()
+	t.Run("Auditor", func(t *testing.T) {
+		t.Parallel()
+		uut := featuresService{}
+		target := struct {
+			Auditor audit.Auditor
+		}{}
+		err := uut.Get(&target)
+		require.NoError(t, err)
+		assert.NotNil(t, target.Auditor)
+	})
+
+	t.Run("NotPointer", func(t *testing.T) {
+		t.Parallel()
+		uut := featuresService{}
+		target := struct {
+			Auditor audit.Auditor
+		}{}
+		err := uut.Get(target)
+		require.Error(t, err)
+		assert.Nil(t, target.Auditor)
+	})
+
+	t.Run("UnknownInterface", func(t *testing.T) {
+		t.Parallel()
+		uut := featuresService{}
+		target := struct {
+			test testInterface
+		}{}
+		err := uut.Get(&target)
+		require.Error(t, err)
+		assert.Nil(t, target.test)
+	})
+
+	t.Run("PointerToNonStruct", func(t *testing.T) {
+		t.Parallel()
+		uut := featuresService{}
+		var target audit.Auditor
+		err := uut.Get(&target)
+		require.Error(t, err)
+		assert.Nil(t, target)
+	})
+
+	t.Run("StructWithNonInterfaces", func(t *testing.T) {
+		t.Parallel()
+		uut := featuresService{}
+		target := struct {
+			N       int64
+			Auditor audit.Auditor
+		}{}
+		err := uut.Get(&target)
+		require.Error(t, err)
+		assert.Nil(t, target.Auditor)
+	})
+}
+
+type testInterface interface {
+	Test() error
+}
diff --git a/enterprise/coderd/features.go b/enterprise/coderd/features.go
@@ -5,17 +5,23 @@ import (
 	"crypto/ed25519"
 	"fmt"
 	"net/http"
+	"reflect"
 	"sync"
 	"time"
 
+	"github.com/coder/coder/enterprise/audit/backends"
+
 	"github.com/cenkalti/backoff/v4"
+	"golang.org/x/xerrors"
 
 	"cdr.dev/slog"
 
 	agpl "github.com/coder/coder/coderd"
+	agplAudit "github.com/coder/coder/coderd/audit"
 	"github.com/coder/coder/coderd/database"
 	"github.com/coder/coder/coderd/httpapi"
 	"github.com/coder/coder/codersdk"
+	"github.com/coder/coder/enterprise/audit"
 )
 
 type Enablements struct {
@@ -29,6 +35,13 @@ type featuresService struct {
 	keys           map[string]ed25519.PublicKey
 	enablements    Enablements
 	resyncInterval time.Duration
+	// enabledImplementations includes an "enabled" implementation of every feature.  This is
+	// initialized at start of day and remains static.  The consequence of this is that these things
+	// are hanging around using memory even if not licensed or in use, but it greatly simplifies the
+	// logic because we don't have to bother creating and destroying them as entitlements change.
+	// If we have a particularly memory-hungry feature in future, we might wish to reconsider this
+	// choice.
+	enabledImplementations agpl.FeatureInterfaces
 
 	mu           sync.RWMutex
 	entitlements entitlements
@@ -44,11 +57,18 @@ func newFeaturesService(
 	enablements Enablements,
 ) agpl.FeaturesService {
 	fs := &featuresService{
-		logger:         logger,
-		database:       db,
-		pubsub:         pubsub,
-		keys:           keys,
-		enablements:    enablements,
+		logger:      logger,
+		database:    db,
+		pubsub:      pubsub,
+		keys:        keys,
+		enablements: enablements,
+		enabledImplementations: agpl.FeatureInterfaces{
+			Auditor: audit.NewAuditor(
+				audit.DefaultFilter,
+				backends.NewPostgres(db, true),
+				backends.NewSlog(logger),
+			),
+		},
 		resyncInterval: 10 * time.Minute,
 		entitlements: entitlements{
 			activeUsers: numericalEntitlement{
@@ -259,3 +279,48 @@ func max(a, b int64) int64 {
 	}
 	return b
 }
+
+func (s *featuresService) Get(ps any) error {
+	if reflect.TypeOf(ps).Kind() != reflect.Pointer {
+		return xerrors.New("input must be pointer to struct")
+	}
+	vs := reflect.ValueOf(ps).Elem()
+	if vs.Kind() != reflect.Struct {
+		return xerrors.New("input must be pointer to struct")
+	}
+	// grab a local copy of entitlements so that we have a consistent set, but aren't keeping it
+	// locked from updates while we process.
+	s.mu.RLock()
+	ent := s.entitlements
+	s.mu.RUnlock()
+
+	for i := 0; i < vs.NumField(); i++ {
+		vf := vs.Field(i)
+		tf := vf.Type()
+		if tf.Kind() != reflect.Interface {
+			return xerrors.Errorf("fields of input struct must be interfaces: %s", tf.String())
+		}
+
+		err := s.setImplementation(ent, vf, tf)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (s *featuresService) setImplementation(ent entitlements, vf reflect.Value, tf reflect.Type) error {
+	// c.f. https://stackoverflow.com/questions/7132848/how-to-get-the-reflect-type-of-an-interface
+	switch tf {
+	case reflect.TypeOf((*agplAudit.Auditor)(nil)).Elem():
+		// Audit logging
+		if !s.enablements.AuditLogs || ent.auditLogs.state == notEntitled {
+			vf.Set(reflect.ValueOf(agpl.DisabledImplementations.Auditor))
+			return nil
+		}
+		vf.Set(reflect.ValueOf(s.enabledImplementations.Auditor))
+		return nil
+	default:
+		return xerrors.Errorf("unable to find implementation of interface %s", tf.String())
+	}
+}