1 files changed, 71 insertions, 0 deletions
diff --git a/pkg/common/sync_subject.go b/pkg/common/sync_subject.go
new file mode 100644
index 0000000..a39d6df
--- /dev/null
+++ b/pkg/common/sync_subject.go
@@ -0,0 +1,71 @@
+package common
+
+import (
+	"github.com/icinga/icingadb/pkg/contracts"
+	v1 "github.com/icinga/icingadb/pkg/icingadb/v1"
+	"github.com/icinga/icingadb/pkg/utils"
+)
+
+// SyncSubject defines information about entities to be synchronized.
+type SyncSubject struct {
+	entity       contracts.Entity
+	factory      contracts.EntityFactoryFunc
+	withChecksum bool
+}
+
+// NewSyncSubject returns a new SyncSubject.
+func NewSyncSubject(factoryFunc contracts.EntityFactoryFunc) *SyncSubject {
+	e := factoryFunc()
+
+	var factory contracts.EntityFactoryFunc
+	if _, ok := e.(contracts.Initer); ok {
+		factory = func() contracts.Entity {
+			e := factoryFunc()
+			e.(contracts.Initer).Init()
+
+			return e
+		}
+	} else {
+		factory = factoryFunc
+	}
+
+	_, withChecksum := e.(contracts.Checksumer)
+
+	return &SyncSubject{
+		entity:       e,
+		factory:      factory,
+		withChecksum: withChecksum,
+	}
+}
+
+// Entity returns one value from the factory. Always returns the same entity.
+func (s SyncSubject) Entity() contracts.Entity {
+	return s.entity
+}
+
+// Factory returns the entity factory function that calls Init() on the created contracts.Entity if applicable.
+func (s SyncSubject) Factory() contracts.EntityFactoryFunc {
+	return s.factory
+}
+
+// FactoryForDelta behaves like Factory() unless s is WithChecksum().
+// In the latter case it returns a factory for EntityWithChecksum instead.
+// Rationale: Sync#ApplyDelta() uses its input entities which are WithChecksum() only for the delta itself
+// and not for insertion into the database, so EntityWithChecksum is enough. And it consumes less memory.
+func (s SyncSubject) FactoryForDelta() contracts.EntityFactoryFunc {
+	if s.withChecksum {
+		return v1.NewEntityWithChecksum
+	}
+
+	return s.factory
+}
+
+// Name returns the declared name of the entity.
+func (s SyncSubject) Name() string {
+	return utils.Name(s.entity)
+}
+
+// WithChecksum returns whether entities from the factory implement contracts.Checksumer.
+func (s SyncSubject) WithChecksum() bool {
+	return s.withChecksum
+}