entity/dag: proper base operation for simplified implementation

- reduce boilerplace necessary to implement an operation
- consolidate what an operation is in the core, which in turn pave the way for a generic cache layer mechanism
- avoid the previously complex unmarshalling process
- support operation metadata from the core
- simplified testing

1 files changed, 39 insertions, 0 deletions

diff --git a/entity/dag/op_noop.go b/entity/dag/op_noop.go
new file mode 100644
index 00000000..2bc53578
--- /dev/null
+++ b/entity/dag/op_noop.go
@@ -0,0 +1,39 @@
+package dag
+
+import (
+	"github.com/MichaelMure/git-bug/entity"
+	"github.com/MichaelMure/git-bug/identity"
+)
+
+var _ Operation = &NoOpOperation[Snapshot]{}
+var _ OperationDoesntChangeSnapshot = &NoOpOperation[Snapshot]{}
+
+// NoOpOperation is an operation that does not change the entity state. It can
+// however be used to store arbitrary metadata in the entity history, for example
+// to support a bridge feature.
+type NoOpOperation[SnapT Snapshot] struct {
+	OpBase
+}
+
+func NewNoOpOp[SnapT Snapshot](opType OperationType, author identity.Interface, unixTime int64) *NoOpOperation[SnapT] {
+	return &NoOpOperation[SnapT]{
+		OpBase: NewOpBase(opType, author, unixTime),
+	}
+}
+
+func (op *NoOpOperation[SnapT]) Id() entity.Id {
+	return IdOperation(op, &op.OpBase)
+}
+
+func (op *NoOpOperation[SnapT]) Apply(snapshot SnapT) {
+	// Nothing to do
+}
+
+func (op *NoOpOperation[SnapT]) Validate() error {
+	if err := op.OpBase.Validate(op, op.OperationType); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (op *NoOpOperation[SnapT]) DoesntChangeSnapshot() {}