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, 68 insertions, 0 deletions

diff --git a/entity/dag/op_set_metadata.go b/entity/dag/op_set_metadata.go
new file mode 100644
index 00000000..bf32171f
--- /dev/null
+++ b/entity/dag/op_set_metadata.go
@@ -0,0 +1,68 @@
+package dag
+
+import (
+	"fmt"
+
+	"github.com/pkg/errors"
+
+	"github.com/MichaelMure/git-bug/entity"
+	"github.com/MichaelMure/git-bug/identity"
+	"github.com/MichaelMure/git-bug/util/text"
+)
+
+var _ Operation = &SetMetadataOperation[Snapshot]{}
+var _ OperationDoesntChangeSnapshot = &SetMetadataOperation[Snapshot]{}
+
+type SetMetadataOperation[SnapT Snapshot] struct {
+	OpBase
+	Target      entity.Id         `json:"target"`
+	NewMetadata map[string]string `json:"new_metadata"`
+}
+
+func NewSetMetadataOp[SnapT Snapshot](opType OperationType, author identity.Interface, unixTime int64, target entity.Id, newMetadata map[string]string) *SetMetadataOperation[SnapT] {
+	return &SetMetadataOperation[SnapT]{
+		OpBase:      NewOpBase(opType, author, unixTime),
+		Target:      target,
+		NewMetadata: newMetadata,
+	}
+}
+
+func (op *SetMetadataOperation[SnapT]) Id() entity.Id {
+	return IdOperation(op, &op.OpBase)
+}
+
+func (op *SetMetadataOperation[SnapT]) Apply(snapshot SnapT) {
+	for _, target := range snapshot.AllOperations() {
+		if target.Id() == op.Target {
+			// Apply the metadata in an immutable way: if a metadata already
+			// exist, it's not possible to override it.
+			for key, value := range op.NewMetadata {
+				target.setExtraMetadataImmutable(key, value)
+			}
+			return
+		}
+	}
+}
+
+func (op *SetMetadataOperation[SnapT]) Validate() error {
+	if err := op.OpBase.Validate(op, op.OperationType); err != nil {
+		return err
+	}
+
+	if err := op.Target.Validate(); err != nil {
+		return errors.Wrap(err, "target invalid")
+	}
+
+	for key, val := range op.NewMetadata {
+		if !text.SafeOneLine(key) {
+			return fmt.Errorf("metadata key is unsafe")
+		}
+		if !text.Safe(val) {
+			return fmt.Errorf("metadata value is not fully printable")
+		}
+	}
+
+	return nil
+}
+
+func (op *SetMetadataOperation[SnapT]) DoesntChangeSnapshot() {}