1 to n support and eventing completeness

Signed-off-by: Kavindu Dodanduwa <kavindudodanduwa@gmail.com>

go.mod

@@ -8,7 +8,7 @@ require (
 	github.com/golang/mock v1.6.0
 	github.com/open-feature/go-sdk-contrib/providers/flagd v0.1.7
 	github.com/open-feature/go-sdk-contrib/tests/flagd v1.1.0
-	golang.org/x/sync v0.1.0
+	golang.org/x/exp v0.0.0-20230522175609-2e198f4a06a1
 	golang.org/x/text v0.10.0
 )
 
@@ -47,7 +47,6 @@ require (
 	go.uber.org/atomic v1.10.0 // indirect
 	go.uber.org/multierr v1.8.0 // indirect
 	go.uber.org/zap v1.24.0 // indirect
-	golang.org/x/exp v0.0.0-20230522175609-2e198f4a06a1 // indirect
 	golang.org/x/net v0.6.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
 	google.golang.org/protobuf v1.28.1 // indirect

go.sum

@@ -388,8 +388,6 @@ golang.org/x/sync v0.0.0-20200317015054-43a5402ce75a/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20200625203802-6e8e738ad208/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
-golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20181116152217-5ac8a444bdc5/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=

pkg/openfeature/api.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/go-logr/logr"
 	"github.com/open-feature/go-sdk/pkg/openfeature/internal"
+	"golang.org/x/exp/maps"
 )
 
 // evaluationAPI wraps OpenFeature evaluation API functionalities
@@ -16,7 +17,7 @@ type evaluationAPI struct {
 	evalCtx         EvaluationContext
 	logger          logr.Logger
 	mu              sync.RWMutex
-	eventExecutor
+	eventExecutor   *eventExecutor
 }
 
 // newEvaluationAPI is a helper to generate an API. Used internally
@@ -46,10 +47,10 @@ func (api *evaluationAPI) setProvider(provider FeatureProvider) error {
 	// Initialize new default provider and shutdown the old one
 	// Provider update must be non-blocking, hence initialization & shutdown happens concurrently
 	oldProvider := api.defaultProvider
-	api.initAndShutdown(provider, oldProvider)
 	api.defaultProvider = provider
 
-	err := api.registerDefaultProvider(provider)
+	api.initNewAndShutdownOld(provider, oldProvider)
+	err := api.eventExecutor.registerDefaultProvider(provider)
 	if err != nil {
 		return err
 	}
@@ -76,10 +77,11 @@ func (api *evaluationAPI) setNamedProvider(clientName string, provider FeaturePr
 
 	// Initialize new default provider and shutdown the old one
 	// Provider update must be non-blocking, hence initialization & shutdown happens concurrently
-	api.initAndShutdown(provider, api.namedProviders[clientName])
+	oldProvider := api.namedProviders[clientName]
 	api.namedProviders[clientName] = provider
 
-	err := api.registerNamedEventingProvider(clientName, provider)
+	api.initNewAndShutdownOld(provider, oldProvider)
+	err := api.eventExecutor.registerNamedEventingProvider(clientName, provider)
 	if err != nil {
 		return err
 	}
@@ -125,6 +127,9 @@ func (api *evaluationAPI) addHooks(hooks ...Hook) {
 }
 
 func (api *evaluationAPI) shutdown() {
+	api.mu.Lock()
+	defer api.mu.Unlock()
+
 	v, ok := api.defaultProvider.(StateHandler)
 	if ok {
 		v.Shutdown()
@@ -161,21 +166,56 @@ func (api *evaluationAPI) forTransaction(clientName string) (FeatureProvider, []
 	return provider, api.hks, api.evalCtx
 }
 
-// initAndShutdown is a helper to initialise new FeatureProvider and shutdown old FeatureProvider.
-// Operation happens concurrently.
-func (api *evaluationAPI) initAndShutdown(newProvider FeatureProvider, oldProvider FeatureProvider) {
-	go func() {
-		v, ok := newProvider.(StateHandler)
-		if ok {
-			v.Init(api.evalCtx)
-		}
-
-		// oldProvider can be nil
-		if oldProvider != nil {
-			v, ok = oldProvider.(StateHandler)
-			if ok {
-				v.Shutdown()
+// initNewAndShutdownOld is a helper to initialise new FeatureProvider and shutdown the old FeatureProvider.
+// Operations happen concurrently.
+func (api *evaluationAPI) initNewAndShutdownOld(newProvider FeatureProvider, oldProvider FeatureProvider) {
+	v, ok := newProvider.(StateHandler)
+	if ok && v.Status() == NotReadyState {
+		go func(provider FeatureProvider, stateHandler StateHandler, evalCtx EvaluationContext, eventChan chan eventPayload) {
+			err := stateHandler.Init(evalCtx)
+			if err != nil {
+				eventChan <- eventPayload{
+					Event{
+						ProviderName:         provider.Metadata().Name,
+						EventType:            ProviderError,
+						ProviderEventDetails: ProviderEventDetails{},
+					}, provider,
+				}
+			} else {
+				eventChan <- eventPayload{
+					Event{
+						ProviderName:         provider.Metadata().Name,
+						EventType:            ProviderReady,
+						ProviderEventDetails: ProviderEventDetails{},
+					}, provider,
+				}
 			}
+		}(newProvider, v, api.evalCtx, api.eventExecutor.eventChan)
+	}
+
+	v, ok = oldProvider.(StateHandler)
+
+	// oldProvider can be nil or without state handling capability
+	if oldProvider == nil || !ok {
+		return
+	}
+
+	// check for multiple bindings
+	if oldProvider == api.defaultProvider || contains(oldProvider, maps.Values(api.namedProviders)) {
+		return
+	}
+
+	go func(forShutdown StateHandler) {
+		forShutdown.Shutdown()
+	}(v)
+}
+
+func contains(provider FeatureProvider, in []FeatureProvider) bool {
+	for _, p := range in {
+		if provider == p {
+			return true
 		}
-	}()
+	}
+
+	return false
 }