Update traversal package to new linking system.

Signed-off-by: Eric Myhre <hash@exultant.us>

traversal/fns.go

@@ -3,33 +3,9 @@ package traversal
 import (
 	"context"
 
-	cid "github.com/ipfs/go-cid"
 	ipld "github.com/ipld/go-ipld-prime"
 )
 
-// An example use of LinkContext in LinkLoader logic might be inspecting the
-// LinkNode, and if it's using the type system, inspecting its Type property;
-// then deciding on whether or not we want to load objects of that Type.
-// This might be used to do a traversal which looks at all directory objects,
-// but not file contents, for example.
-type LinkContext struct {
-	LinkPath   ipld.Path
-	LinkNode   ipld.Node // has the cid again, but also might have type info // always zero for writing new nodes, for obvi reasons.
-	ParentNode ipld.Node
-}
-
-type LinkLoader func(context.Context, cid.Cid, LinkContext) (ipld.Node, error)
-
-// One presumes implementations will also *save* the content somewhere.
-// The LinkContext parameter is a nod to this -- none of those parameters
-// are relevant to the generation of the Cid itself, but perhaps one might
-// want to use them when deciding where to store some files, etc.
-type LinkBuilder func(
-	ctx context.Context,
-	node ipld.Node, lnkCtx LinkContext,
-	multicodecType uint64, multihashType uint64, multihashLength int,
-) (cid.Cid, error)
-
 // VisitFn is a read-only visitor.
 type VisitFn func(TraversalProgress, ipld.Node) error
 
@@ -45,14 +21,14 @@ type TraversalReason byte // enum = SelectionMatch | SelectionParent | Selection
 type TraversalProgress struct {
 	*TraversalConfig
 	Path      ipld.Path // Path is how we reached the current point in the traversal.
-	LastBlock struct {  // LastBlock stores the Path and CID of the last block edge we had to load.  (It will always be zero in traversals with no linkloader.)
+	LastBlock struct {  // LastBlock stores the Path and Link of the last block edge we had to load.  (It will always be zero in traversals with no linkloader.)
 		ipld.Path
-		cid.Cid
+		ipld.Link
 	}
 }
 
 type TraversalConfig struct {
 	Ctx        context.Context // Context carried through a traversal.  Optional; use it if you need cancellation.
-	LinkLoader LinkLoader
-	// `blockWriter func(Context, Node, multicodec(?)) (CID, error)` probably belongs here.
+	LinkLoader ipld.Loader     // Loader used for automatic link traversal.
+	LinkStorer ipld.Storer     // Storer used if any mutation features (e.g. traversal.Transform) are used.
 }