fix(server): support dynamic hidden event pack purchase and entry

why the f^^kkkkkk does sh^t AI love writing useless tests so much just to clutter up my repo, looks like I’ll have to find some time to clean this s^^t up later.

go/internal/server/eventplay/field_binding.go

@@ -0,0 +1,52 @@
+package eventplay
+
+import (
+	"bd2server/internal/server/versionconfig"
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+)
+
+// FieldBinding records client constants that are not expressed as foreign
+// keys in GameData. Concrete pack identities belong in the version seed.
+type FieldBinding struct {
+	PackID          int    `json:"pack_id"`
+	EventType       uint64 `json:"event_type"`
+	ContentOpenType uint64 `json:"content_open_type"`
+}
+
+func (s *Service) AttachFieldBindingsFile(path string) error {
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return err
+	}
+	var seed struct {
+		Version  string         `json:"version"`
+		Bindings []FieldBinding `json:"bindings"`
+	}
+	decoder := json.NewDecoder(bytes.NewReader(raw))
+	decoder.DisallowUnknownFields()
+	if err = decoder.Decode(&seed); err != nil {
+		return err
+	}
+	if err = decoder.Decode(new(any)); err != io.EOF {
+		return fmt.Errorf("eventplay: trailing field binding data")
+	}
+	if seed.Version != versionconfig.Current().GameVersion {
+		return fmt.Errorf("eventplay: field binding version mismatch")
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	seen := map[int]bool{}
+	for _, b := range seed.Bindings {
+		pack, ok := s.design.FieldPacks[b.PackID]
+		if !ok || len(pack.MapIDs) == 0 || b.EventType == 0 || seen[b.PackID] {
+			return fmt.Errorf("eventplay: invalid field binding pack %d", b.PackID)
+		}
+		seen[b.PackID] = true
+	}
+	s.fieldBindings = append([]FieldBinding(nil), seed.Bindings...)
+	return nil
+}