90 lines
2.3 KiB
Go
90 lines
2.3 KiB
Go
package utils
|
|
|
|
import (
|
|
"bytes"
|
|
"context"
|
|
"fmt"
|
|
"io"
|
|
|
|
// must be imported to init() raw-codec support
|
|
_ "github.com/ipld/go-ipld-prime/codec/raw"
|
|
|
|
"github.com/ipfs/go-cid"
|
|
mdagipld "github.com/ipfs/go-ipld-format"
|
|
dagpb "github.com/ipld/go-codec-dagpb"
|
|
"github.com/ipld/go-ipld-prime"
|
|
cidlink "github.com/ipld/go-ipld-prime/linking/cid"
|
|
basicnode "github.com/ipld/go-ipld-prime/node/basic"
|
|
"github.com/ipld/go-ipld-prime/traversal"
|
|
"github.com/ipld/go-ipld-prime/traversal/selector"
|
|
selectorparse "github.com/ipld/go-ipld-prime/traversal/selector/parse"
|
|
)
|
|
|
|
func TraverseDag(
|
|
ctx context.Context,
|
|
ds mdagipld.DAGService,
|
|
startFrom cid.Cid,
|
|
optionalSelector ipld.Node,
|
|
visitCallback traversal.AdvVisitFn,
|
|
) error {
|
|
|
|
if optionalSelector == nil {
|
|
optionalSelector = selectorparse.CommonSelector_MatchAllRecursively
|
|
}
|
|
|
|
parsedSelector, err := selector.ParseSelector(optionalSelector)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
// not sure what this is for TBH: we also provide ctx in &traversal.Config{}
|
|
linkContext := ipld.LinkContext{Ctx: ctx}
|
|
|
|
// this is what allows us to understand dagpb
|
|
nodePrototypeChooser := dagpb.AddSupportToChooser(
|
|
func(ipld.Link, ipld.LinkContext) (ipld.NodePrototype, error) {
|
|
return basicnode.Prototype.Any, nil
|
|
},
|
|
)
|
|
|
|
// this is how we implement GETs
|
|
linkSystem := cidlink.DefaultLinkSystem()
|
|
linkSystem.StorageReadOpener = func(lctx ipld.LinkContext, lnk ipld.Link) (io.Reader, error) {
|
|
cl, isCid := lnk.(cidlink.Link)
|
|
if !isCid {
|
|
return nil, fmt.Errorf("unexpected link type %#v", lnk)
|
|
}
|
|
|
|
node, err := ds.Get(lctx.Ctx, cl.Cid)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
return bytes.NewBuffer(node.RawData()), nil
|
|
}
|
|
|
|
// this is how we pull the start node out of the DS
|
|
startLink := cidlink.Link{Cid: startFrom}
|
|
startNodePrototype, err := nodePrototypeChooser(startLink, linkContext)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
startNode, err := linkSystem.Load(
|
|
linkContext,
|
|
startLink,
|
|
startNodePrototype,
|
|
)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
// this is the actual execution, invoking the supplied callback
|
|
return traversal.Progress{
|
|
Cfg: &traversal.Config{
|
|
Ctx: ctx,
|
|
LinkSystem: linkSystem,
|
|
LinkTargetNodePrototypeChooser: nodePrototypeChooser,
|
|
},
|
|
}.WalkAdv(startNode, parsedSelector, visitCallback)
|
|
}
|