try writemodel

internal/eventstore/v2/write_model.go

@@ -0,0 +1,45 @@
+package eventstore
+
+func NewReadModel() *ReadModel {
+	return &ReadModel{
+		Events: []EventReader{},
+	}
+}
+
+//WriteModel is the minimum representation of a command side view model.
+// It implements a basic reducer
+// it's purpose is to reduce events to create new ones
+type WriteModel struct {
+	AggregateID       string        `json:"-"`
+	ProcessedSequence uint64        `json:"-"`
+	Events            []EventReader `json:"-"`
+}
+
+//AppendEvents adds all the events to the read model.
+// The function doesn't compute the new state of the read model
+func (rm *WriteModel) AppendEvents(events ...EventReader) *WriteModel {
+	rm.Events = append(rm.Events, events...)
+	return rm
+}
+
+//Reduce is the basic implementaion of reducer
+// If this function is extended the extending function should be the last step
+func (rm *WriteModel) Reduce() error {
+	if len(rm.Events) == 0 {
+		return nil
+	}
+
+	if rm.AggregateID == "" {
+		rm.AggregateID = rm.Events[0].AggregateID()
+	}
+	if rm.ResourceOwner == "" {
+		rm.ResourceOwner = rm.Events[0].ResourceOwner()
+	}
+
+	rm.ProcessedSequence = rm.Events[len(rm.Events)-1].Sequence()
+
+	// all events processed and not needed anymore
+	rm.Events = nil
+	rm.Events = []EventReader{}
+	return nil
+}