feat(hooks): add onConfigDonloaded hook

config_fetcher.go

@@ -4,13 +4,14 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"github.com/configcat/go-sdk/v9/configcatcache"
 	"io"
 	"net/http"
 	"os"
 	"sync"
 	"sync/atomic"
 	"time"
+
+	"github.com/configcat/go-sdk/v9/configcatcache"
 )
 
 const (
@@ -209,6 +210,12 @@ func (f *configFetcher) refreshIfOlder(ctx context.Context, before time.Time, wa
 func (f *configFetcher) fetcher(prevConfig *config) {
 	defer f.wg.Done()
 	config, newURL, err := f.fetchConfig(f.ctx, f.baseURL, prevConfig)
+
+	// Call OnConfigDownloaded hook only for HTTP requests (not cache or local-only)
+	if !f.isOffline() && (f.overrides == nil || f.overrides.Behavior != LocalOnly) {
+		f.callOnConfigDownloaded(err)
+	}
+
 	f.mu.Lock()
 	defer f.mu.Unlock()
 	if err != nil {
@@ -422,6 +429,13 @@ func (f *configFetcher) fetchHTTPWithoutRedirect(ctx context.Context, baseURL st
 	return nil, &fetcherError{EventId: 1101, Err: fmt.Errorf("unexpected HTTP response was received while trying to fetch config JSON: %v", response.Status)}
 }
 
+// callOnConfigDownloaded calls the OnConfigDownloaded hook if it's configured.
+func (f *configFetcher) callOnConfigDownloaded(err error) {
+	if f.hooks != nil && f.hooks.OnConfigDownloaded != nil {
+		go f.hooks.OnConfigDownloaded(err)
+	}
+}
+
 func pollingModeToIdentifier(pollingMode PollingMode) string {
 	switch pollingMode {
 	case AutoPoll:

configcat_client.go

@@ -24,6 +24,9 @@ type Hooks struct {
 
 	// OnConfigChanged is called, when a new config.json has downloaded.
 	OnConfigChanged func()
+
+	// OnConfigDownloaded is called every time a config download attempt is made.
+	OnConfigDownloaded func(err error)
 }
 
 // Config describes configuration options for the Client.

configcat_client_test.go

@@ -1138,6 +1138,73 @@ func rootNodeWithKeyValueType(key string, value interface{}, t SettingType) *Con
 	}
 }
 
+func TestClient_Hooks_OnConfigDownloaded(t *testing.T) {
+	tests := []struct {
+		name         string
+		expectError  bool
+		refreshTwice bool
+	}{
+		{
+			name:         "successful_download",
+			expectError:  false,
+			refreshTwice: false,
+		},
+		{
+			name:         "successful_download_with_refresh",
+			expectError:  false,
+			refreshTwice: true,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			c := qt.New(t)
+			srv := newConfigServer(t)
+			srv.setResponse(configResponse{
+				body: contentForIntegrationTestKey("PKDVCLf-Hq-h-kCzMp-L7Q/psuH7BGHoUmdONrzzUOY7A"),
+			})
+
+			downloadedChan := make(chan error, 10)
+			cfg := srv.config()
+			cfg.Hooks = &Hooks{OnConfigDownloaded: func(err error) {
+				downloadedChan <- err
+			}}
+			client := NewCustomClient(cfg)
+			defer client.Close()
+
+			// Wait for the initial config download
+			select {
+			case err := <-downloadedChan:
+				if test.expectError {
+					c.Assert(err, qt.Not(qt.IsNil))
+				} else {
+					c.Assert(err, qt.IsNil)
+				}
+			case <-time.After(time.Second):
+				t.Fatalf("timed out waiting for OnConfigDownloaded hook")
+			}
+
+			if test.refreshTwice {
+				// Trigger a refresh to get another download event
+				err := client.Refresh(context.Background())
+				c.Assert(err, qt.IsNil)
+
+				// Should get another download notification
+				select {
+				case err := <-downloadedChan:
+					if test.expectError {
+						c.Assert(err, qt.Not(qt.IsNil))
+					} else {
+						c.Assert(err, qt.IsNil)
+					}
+				case <-time.After(time.Second):
+					t.Fatalf("timed out waiting for second OnConfigDownloaded hook")
+				}
+			}
+		})
+	}
+}
+
 type mockHTTPTransport struct {
 	requests  []*http.Request
 	responses []*http.Response