update the code

cmd/backoffice/fileserver.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"io"
 	"io/fs"
+	"log"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -17,6 +18,7 @@ import (
 
 	"git.tornberg.me/go-cart-actor/pkg/actor"
 	"git.tornberg.me/go-cart-actor/pkg/cart"
+	"github.com/gogo/protobuf/proto"
 )
 
 type FileServer struct {
@@ -232,6 +234,22 @@ type JsonError struct {
 	Error string `json:"error"`
 }
 
+func acceptAll(_ proto.Message, _ int, _ time.Time) bool {
+	return true
+}
+
+func acceptUntilIndex(maxIndex int) func(msg proto.Message, index int, when time.Time) bool {
+	return func(msg proto.Message, index int, when time.Time) bool {
+		return index < maxIndex
+	}
+}
+
+func acceptUntilTimestamp(until time.Time) func(msg proto.Message, index int, when time.Time) bool {
+	return func(msg proto.Message, index int, when time.Time) bool {
+		return when.Before(until)
+	}
+}
+
 func (fs *FileServer) CartHandler(w http.ResponseWriter, r *http.Request) {
 	idStr := r.PathValue("id")
 	if idStr == "" {
@@ -243,10 +261,29 @@ func (fs *FileServer) CartHandler(w http.ResponseWriter, r *http.Request) {
 		writeJSON(w, http.StatusBadRequest, JsonError{Error: "invalid id"})
 		return
 	}
+	// parse query parameters for filtering
+	query := r.URL.Query()
+	filterFunction := acceptAll
+	if maxIndexStr := query.Get("maxIndex"); maxIndexStr != "" {
+		log.Printf("filter maxIndex: %s", maxIndexStr)
+		maxIndex, err := strconv.Atoi(maxIndexStr)
+		if err != nil {
+			writeJSON(w, http.StatusBadRequest, JsonError{Error: "invalid maxIndex"})
+			return
+		}
+		filterFunction = acceptUntilIndex(maxIndex)
+	} else if untilStr := query.Get("until"); untilStr != "" {
+		log.Printf("filter until: %s", untilStr)
+		until, err := time.Parse(time.RFC3339, untilStr)
+		if err != nil {
+			writeJSON(w, http.StatusBadRequest, JsonError{Error: "invalid until timestamp"})
+			return
+		}
+		filterFunction = acceptUntilTimestamp(until)
+	}
 	// reconstruct state from event log if present
 	grain := cart.NewCartGrain(id, time.Now())
-
-	err := fs.storage.LoadEvents(r.Context(), id, grain)
+	err := fs.storage.LoadEventsFunc(r.Context(), id, grain, filterFunction)
 	if err != nil {
 		writeJSON(w, http.StatusInternalServerError, JsonError{Error: err.Error()})
 		return