Add nodes for attestations, artifacts and builders

Implements most of guacsec#11.

Still working on the testing interface for this as I also want to be
able to write and read subgraphs from DB (guacsec#10/guacsec#12/guacsec#14).

Signed-off-by: Mihai Maruseac <mihaimaruseac@google.com>

pkg/assembler/assembler.go

@@ -17,43 +17,66 @@ package assembler
 
 type assembler struct{} //nolint: unused
 
-// Identifiable implements the ability to retrieve a set of
-// attributes such that a graph query is able to identify a
-// GuacNode or GuacEdge uniquely (or as a GuacHyperNode).
-type Identifiable interface {
-	// Identifiers returns a map of fields and values which
-	// can be used to identify an object in the graph.
-	Identifiers() map[string]interface{}
-}
-
 // GuacNode represents a node in the GUAC graph
 type GuacNode interface {
-	Identifiable
-
 	// Type returns the type of node
 	Type() string
 
 	// Properties returns the list of properties of the node
 	Properties() map[string]interface{}
+
+	// Attributes returns the names of the properties of the node.
+	//
+	// If a string `s` is in the list returned by `Attributes` then it
+	// should also be a key in the map returned by `Properties`.
+	Attributes() []string
+
+	// IdentifiableAttributes returns a list of tuples of property names
+	// that can uniquely specify a GuacNode.
+	//
+	// Any string found in a tuple returned by `IdentifiableAttributes`
+	// must also be returned by `Attributes`.
+	IdentifiableAttributes() [][]string
 }
 
 // GuacEdge represents an edge in the GUAC graph
 type GuacEdge interface {
-	Identifiable
+	// Type returns the type of edge
+	Type() string
 
 	// Nodes returns the (v,u) nodes of the edge
-	// where v--edge-->u for directional edges.
+	//
+	// For directional edges: v-[edge]->u.
+	// For non-directional edges there is no guaranteed order.
 	Nodes() (v, u GuacNode)
 
-	// Type returns the type of edge
-	Type() string
-
-	// Properties returns the list of properties of the node
+	// Properties returns the list of properties of the edge
 	Properties() map[string]interface{}
+
+	// Attributes returns the names of the properties of the edge.
+	//
+	// If a string `s` is in the list returned by `Attributes` then it
+	// should also be a key in the map returned by `Properties`.
+	Attributes() []string
+
+	// IdentifiableAttributes returns a list of tuples of property names
+	// that can uniquely specify a GuacEdge, as an alternative to the two
+	// node endpoints.
+	//
+	// Any string found in a tuple returned by `IdentifiableAttributes`
+	// must also be returned by `Attributes`.
+	//
+	// TODO(mihaimaruseac): We might not need this?
+	IdentifiableAttributes() [][]string
 }
 
-// AssemblerInput represents the inputs to add to the graph
-type AssemblerInput struct {
+// Subgraph represents a subgraph read from the database or written to it.
+type Subgraph struct {
 	V []GuacNode
 	E []GuacEdge
 }
+
+// TODO(mihaimaruseac): Write queries to write/read subgraphs from DB?
+
+// AssemblerInput represents the inputs to add to the graph
+type AssemblerInput = Subgraph

pkg/assembler/nodes.go

@@ -16,9 +16,80 @@
 package assembler
 
 // ArtifactNode is a node that represents an artifact
-// TODO: implement GuacNode
-type ArtifactNode struct{}
+type ArtifactNode struct{
+	Name     string
+	Checksum string
+}
+
+func (an* ArtifactNode) Type() string {
+	return "Artifact"
+}
+
+func (an *ArtifactNode) Properties() map[string]interface{} {
+	properties := make(map[string]interface{})
+	properties["name"]     = an.Name
+	properties["checksum"] = an.Checksum
+	return properties
+}
+
+func (an *ArtifactNode) Attributes() []string {
+	return []string{"name", "checksum"}
+}
+
+func (an *ArtifactNode) IdentifiableAttributes() [][]string {
+	// An artifact can be uniquely identified by checksum
+	return [][]string{{"checksum"}}
+}
 
 // AttestationNode is a node that represents an attestation
-// TODO: implement GuacNode
-type AttestationNode struct{}
+type AttestationNode struct{
+	// TODO(mihaimaruseac): Unsure what fields to store here
+	File     string
+	Checksum string
+}
+
+func (an* AttestationNode) Type() string {
+	return "Attestation"
+}
+
+func (an *AttestationNode) Properties() map[string]interface{} {
+	properties := make(map[string]interface{})
+	properties["file"]     = an.File
+	properties["checksum"] = an.Checksum
+	return properties
+}
+
+func (an *AttestationNode) Attributes() []string {
+	return []string{"file", "checksum"}
+}
+
+func (an *AttestationNode) IdentifiableAttributes() [][]string {
+	// An attestation can be uniquely identified by filename?
+	return [][]string{{"file"}}
+}
+
+// BuilderNode is a node that represents an attestation
+type BuilderNode struct{
+	BuilderType     string
+	BuilderId       string
+}
+
+func (bn* BuilderNode) Type() string {
+	return "Builder"
+}
+
+func (bn *BuilderNode) Properties() map[string]interface{} {
+	properties := make(map[string]interface{})
+	properties["type"] = bn.BuilderType
+	properties["id"]   = bn.BuilderId
+	return properties
+}
+
+func (bn *BuilderNode) Attributes() []string {
+	return []string{"type", "id"}
+}
+
+func (bn *BuilderNode) IdentifiableAttributes() [][]string {
+	// A builder needs both type and id to be identified
+	return [][]string{{"type", "id"}}
+}