Merge pull request #17 from ipfs/chore/mock-selector-interfaces-4

Setup IPLD Bridge and provide mock-interface and "beta" implementation

docs/go-graphsync.puml

@@ -4,11 +4,51 @@
 
 package "go-ipld-prime" {
   interface Node {
-
   }
+  interface NodeBuilder {
+  }
+  interface Path {
+  }
+  package traversal {
+    package selector {
       interface Selector {
       }
+      object "PackagePublicFunctions" as goSelectorPF {
+        ReifySelector(cidRootedSelector Node) (Selector, error)
+      }
+    }
+    interface AdvVisitFn {
+    }
+    class TraversalConfig {
+      ctx context.Context
+      linkLoader LinkLoader
+    }
+    class TraversalProgress {
+      TraverseInformatively(Node, Selector, AdvVisitFn)
+    }
+
+    TraversalProgress *-- TraversalConfig
+  }
+
+  package repose {
+    interface RawLoader {
+    }
+
+    interface MulticodecDecodeTable {
+    }
+
+    interface NodeBuilderChooser {
+    }
 
+    interface LinkLoader {
+    }
+
+    object "Package Public Functions" as goIPLDReposePf {
+      ComposeLinkLoader(RawLoader, NodeBuilderChooser, MulticodecDecodeTable)
+      EncoderDagCbor(Node, io.Writer)
+      DecodeDagCbor(NodeBuilder, io.Writer)
+    }  
+  }
 }
 
 package "go-graphsync" {
@@ -17,11 +57,16 @@ package "go-graphsync" {
       network : GraphySyncNetwork
       requestManager : RequestManager
       responseManager: ResponseManager
-      Request(p peer.ID, selector Selector, root Cid) chan Block
+      ipldBridge: IPLDBridge
+      rawLoader: RawLoader
+      
+      Request(ctx context.Context, p peer.ID, cidRootedSelector Node) chan Block
       ReceiveMessage(ctx context.Context, sender peer.ID, incoming GraphSyncMessage)
       ReceiveError(error)
     }
 
+    GraphSync *-- RawLoader
+
   package network {
     
     interface Receiver {
@@ -58,8 +103,9 @@ package "go-graphsync" {
   package requestmanager {
   class RequestManager {
     network : GraphSyncNetwork
+    ipldBridge: GraphSyncNetwork
 
-    SendRequest(p peer.ID, selector Selector, root Cid) chan Block
+    SendRequest(ctx context.Context, p peer.ID, cidRootedSelector Node) chan Block
     ProcessResponses(responses []GraphSyncResponse)
   }
   RequestManager *-- GraphSyncNetwork
@@ -69,10 +115,14 @@ package "go-graphsync" {
   package responsemanager {
   class ResponseManager {
     network : GraphySyncNetwork
+    ipldBridge: IPLDBridge
+    rawLoader: RawLoader
+
     ProcessRequests(p peer.ID, requests []GraphSyncRequests)
   }
   ResponseManager *-- GraphSyncNetwork
   GraphSync *-- ResponseManager
+  ResponseManager *-- RawLoader
   }
   package message {
     object "Package Public Functions" as goGraphSyncMessagePF {
@@ -111,8 +161,39 @@ package "go-graphsync" {
     
   }
 
+  package ipldbridge {
+    interface IPLDBridge {
+      ComposeLinkLoader(actualLoader RawLoader) LinkLoader
+	    ValidateSelectorSpec(cidRootedSelector ipld.Node) []error
+	    EncodeNode(ipld.Node) ([]byte, error)
+	    DecodeNode([]byte) (ipld.Node, error)
+	    DecodeSelectorSpec(cidRootedSelector ipld.Node) (ipld.Node, Selector, error)
+	    Traverse(ctx context.Context, loader LinkLoader, root ipld.Node, s Selector, fn AdvVisitFn) error
+    }
+
+    GraphSync *-- IPLDBridge
+    RequestManager *-- IPLDBridge
+    ResponseManager *-- IPLDBridge
+  
+    class ipldBridge {
+      nodeBuilderChooser: NodeBuilderChooser
+      multicodecTable: MulticodecDecodeTable
+    }
+
+    object "PackagePublicFunctions" as goIPLDBridge {
+      NewIPLDBridge(nodeBuilderChooser NodeBuilderChooser, multicodecTable MulticodecDecodeTable) IPLDBridge
+    }
+
+    IPLDBridge <|-- ipldBridge
+    goIPLDBridge .. ipldBridge 
+    ipldBridge *-- MulticodecDecodeTable
+    ipldBridge *-- NodeBuilderChooser
+    ipldBridge .. TraversalProgress
+    ipldBridge .. goSelectorPF
+    ipldBridge .. goIPLDReposePf
+  }
   object "PackagePublicFunctions" as goGraphsyncPf {
-    New(ctx context.Context, network GraphSyncNetwork) GraphSync
+    New(ctx context.Context, network GraphSyncNetwork, rawLoader RawLoader, multicodecDecodeTable MulticodecDecodeTable, nodeBuilderChooser NodeBuilderChooser) GraphSync
   }
 
 }
@@ -121,12 +202,18 @@ package "go-filecoin" {
   class "go-filecoin" {
     graphSync : GraphSync
     host: libp2pHost.Host
+    nodeBuilderChooser: NodeBuilderChooser
+    multicodecTable: MulticodecDecodeTable
+    rawLoader: RawLoader
   }
 
   "go-filecoin" *-- GraphSync
   "go-filecoin" .. goGraphsyncPf
   "go-filecoin" .. goGraphSyncNetworkPF
-  "go-filecoin" .. Selector
+  "go-filecoin" .. goIPLDBridge
+  "go-filecoin" *-- RawLoader
+  "go-filecoin" *-- MulticodecDecodeTable
+  "go-filecoin" *-- NodeBuilderChooser
 
 }
 

go.mod

+module github.com/ipfs/go-graphsync
+
+go 1.12
+
+require (
+	github.com/gogo/protobuf v1.2.1
+	github.com/ipfs/go-block-format v0.0.2
+	github.com/ipfs/go-cid v0.0.1
+	github.com/ipfs/go-ipfs-blocksutil v0.0.1
+	github.com/ipfs/go-log v0.0.1
+	github.com/ipld/go-ipld-prime v0.0.0-20190306022502-066284669cf6
+	github.com/jbenet/go-random v0.0.0-20190219211222-123a90aedc0c
+	github.com/libp2p/go-libp2p-host v0.0.1
+	github.com/libp2p/go-libp2p-net v0.0.1
+	github.com/libp2p/go-libp2p-peer v0.0.1
+	github.com/libp2p/go-libp2p-peerstore v0.0.1
+	github.com/libp2p/go-libp2p-protocol v0.0.1
+	github.com/multiformats/go-multihash v0.0.1
+	github.com/polydawn/refmt v0.0.0-20190221155625-df39d6c2d992 // indirect
+)

go.sum

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ipldbridge/ipld_impl.go

+package ipldbridge
+
+import (
+	"bytes"
+	"context"
+	"errors"
+
+	ipld "github.com/ipld/go-ipld-prime"
+	ipldfree "github.com/ipld/go-ipld-prime/impl/free"
+	ipldrepose "github.com/ipld/go-ipld-prime/repose"
+	ipldtraversal "github.com/ipld/go-ipld-prime/traversal"
+	ipldselector "github.com/ipld/go-ipld-prime/traversal/selector"
+	ipldtypesystem "github.com/ipld/go-ipld-prime/typed/system"
+)
+
+// not sure how these will come into being or from where
+var cidRootedSelectorType ipldtypesystem.Type
+var universe ipldtypesystem.Universe
+
+// TraversalConfig is an alias from ipld, in case it's renamed/moved.
+type TraversalConfig = ipldtraversal.TraversalConfig
+
+type ipldBridge struct {
+	nodeBuilderChooser NodeBuilderChooser
+	multicodecTable    MulticodecDecodeTable
+}
+
+// NewIPLDBridge returns an IPLD Bridge.
+func NewIPLDBridge(nodeBuilderChooser NodeBuilderChooser,
+	multicodecTable MulticodecDecodeTable) IPLDBridge {
+	return &ipldBridge{nodeBuilderChooser, multicodecTable}
+}
+
+func (rb *ipldBridge) ComposeLinkLoader(
+	actualLoader RawLoader) LinkLoader {
+	return ipldrepose.ComposeLinkLoader(actualLoader, rb.nodeBuilderChooser, rb.multicodecTable)
+}
+
+func (rb *ipldBridge) Traverse(ctx context.Context, loader LinkLoader, root ipld.Node, s Selector, fn AdvVisitFn) error {
+	config := &TraversalConfig{Ctx: ctx, LinkLoader: loader}
+	return TraversalProgress{TraversalConfig: config}.TraverseInformatively(root, s, fn)
+}
+
+func (rb *ipldBridge) ValidateSelectorSpec(cidRootedSelector ipld.Node) []error {
+	return ipldtypesystem.Validate(universe, cidRootedSelectorType, cidRootedSelector)
+}
+
+func (rb *ipldBridge) EncodeNode(node ipld.Node) ([]byte, error) {
+	var buffer bytes.Buffer
+	err := ipldrepose.EncoderDagCbor(node, &buffer)
+	if err != nil {
+		return nil, err
+	}
+	return buffer.Bytes(), nil
+}
+
+func (rb *ipldBridge) DecodeNode(encoded []byte) (ipld.Node, error) {
+	reader := bytes.NewReader(encoded)
+	return ipldrepose.DecoderDagCbor(ipldfree.NodeBuilder(), reader)
+}
+
+func (rb *ipldBridge) DecodeSelectorSpec(cidRootedSelector ipld.Node) (ipld.Node, Selector, error) {
+
+	errs := rb.ValidateSelectorSpec(cidRootedSelector)
+	if len(errs) != 0 {
+		return nil, nil, errors.New("Node does not validate as selector spec")
+	}
+
+	root, err := cidRootedSelector.TraverseField("root")
+	if err != nil {
+		return nil, nil, err
+	}
+	rootCid, err := root.AsLink()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	node, err := ipldfree.NodeBuilder().CreateLink(rootCid)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	selector, err := ipldselector.ReifySelector(cidRootedSelector)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return node, selector, nil
+}

ipldbridge/ipldbridge.go

+package ipldbridge
+
+import (
+	"context"
+
+	ipld "github.com/ipld/go-ipld-prime"
+	ipldrepose "github.com/ipld/go-ipld-prime/repose"
+	ipldtraversal "github.com/ipld/go-ipld-prime/traversal"
+	ipldselector "github.com/ipld/go-ipld-prime/traversal/selector"
+)
+
+// MulticodecDecodeTable is an alias from ipld, in case it's renamed/moved.
+type MulticodecDecodeTable = ipldrepose.MulticodecDecodeTable
+
+// NodeBuilderChooser is an an alias from ipld, in case it's renamed/moved.
+type NodeBuilderChooser = ipldrepose.NodeBuilderChooser
+
+// LinkLoader is alias from ipld, in case it.s renamed/moved.
+type LinkLoader = ipldtraversal.LinkLoader
+
+// RawLoader is an alias from ipld, in case it's renamed/moved.
+type RawLoader = ipldrepose.ActualLoader
+
+// AdvVisitFn is an alias from ipld, in case it's renamed/moved.
+type AdvVisitFn = ipldtraversal.AdvVisitFn
+
+// Selector is an alias from ipld, in case it's renamed/moved.
+type Selector = ipldselector.Selector
+
+// LinkContext is an alias from ipld, in case it's renamed/moved.
+type LinkContext = ipldtraversal.LinkContext
+
+// TraversalProgress is an alias from ipld, in case it's renamed/moved.
+type TraversalProgress = ipldtraversal.TraversalProgress
+
+// TraversalReason is an alias from ipld, in case it's renamed/moved.
+type TraversalReason = ipldtraversal.TraversalReason
+
+// IPLDBridge is an interface for making calls to IPLD, which can be
+// replaced with alternative implementations
+type IPLDBridge interface {
+	// ComposeLinkLoader converts a raw block loader into an IPLD node loader.
+	ComposeLinkLoader(actualLoader RawLoader) LinkLoader
+
+	// ValidateSelectorSpec verifies if a node matches the selector spec.
+	ValidateSelectorSpec(cidRootedSelector ipld.Node) []error
+
+	// EncodeNode encodes an IPLD Node to bytes for network transfer.
+	EncodeNode(ipld.Node) ([]byte, error)
+
+	// DecodeNode decodes bytes crossing a network to an IPLD Node.
+	DecodeNode([]byte) (ipld.Node, error)
+
+	// DecodeSelectorSpec checks if a generic IPLD node is a selector spec,
+	// and if so, converts it to a root node and a go-ipld-prime Selector.
+	DecodeSelectorSpec(cidRootedSelector ipld.Node) (ipld.Node, Selector, error)
+
+	// Traverse performs a selector traversal, starting at a given root, using the given selector,
+	// and the given link loader. The given visit function will be called for each node
+	// visited.
+	Traverse(ctx context.Context, loader LinkLoader, root ipld.Node, s Selector, fn AdvVisitFn) error
+}

package.json

-{
-  "author": "hannahhoward",
-  "bugs": {
-    "url": "https://github.com/ipfs/go-graphsync"
-  },
-  "gx": {
-    "dvcsimport": "github.com/ipfs/go-graphsync"
-  },
-  "gxDependencies": [
-    {
-      "author": "whyrusleeping",
-      "hash": "QmYxivS34F2M2n44WQQnRHGAKS8aoRUxwGpi9wk4Cdn4Jf",
-      "name": "go-libp2p",
-      "version": "6.0.30"
-    },
-    {
-      "author": "hsanjuan",
-      "hash": "QmVZ6cQXHoTQja4oo9GhhHZi7dThi4x98mRKgGtKnTy37u",
-      "name": "go-ipfs-routing",
-      "version": "0.1.13"
-    },
-    {
-      "author": "whyrusleeping",
-      "hash": "QmNvHv84aH2qZafDuSdKJCQ1cvPZ1kmQmyD4YtzjUHuk9v",
-      "name": "go-testutil",
-      "version": "1.2.15"
-    },
-    {
-      "author": "whyrusleeping",
-      "hash": "QmY5Grm8pJdiSSVsYxx4uNRgweY72EmYwuSDbRnbFok3iY",
-      "name": "go-libp2p-peer",
-      "version": "3.0.0"
-    },
-    {
-      "author": "whyrusleeping",
-      "hash": "QmdxUuburamoF6zF9qjeQC4WYcWGbWuRmdLacMEsW8ioD8",
-      "name": "gogo-protobuf",
-      "version": "0.0.0"
-    },
-    {
-      "author": "hsanjuan",
-      "hash": "QmZUbTDJ39JpvtFCSubiWeUTQRvMA1tVE5RZCJrY4oeAsC",
-      "name": "go-ipfs-pq",
-      "version": "0.0.1"
-    },
-    {
-      "author": "whyrusleeping",
-      "hash": "QmNohiVssaPw3KVLZik59DBVGTSm2dGvYT9eoXt5DQ36Yz",
-      "name": "go-ipfs-util",
-      "version": "1.2.9"
-    },
-    {
-      "author": "whyrusleeping",
-      "hash": "QmaoXrM4Z41PD48JY36YqQGKQpLGjyLA2cKcLsES7YddAq",
-      "name": "go-libp2p-host",
-      "version": "3.0.21"
-    },
-    {
-      "author": "hsanjuan",
-      "hash": "QmUe1WCHkQaz4UeNKiHDUBV2T6i9prc3DniqyHPXyfGaUq",
-      "name": "go-ipfs-delay",
-      "version": "0.1.0"
-    },
-    {
-      "hash": "QmcuXC5cxs79ro2cUuHs4HQ2bkDLJUYokwL8aivcX6HW3C",
-      "name": "go-log",
-      "version": "1.5.8"
-    },
-    {
-      "author": "whyrusleeping",
-      "hash": "QmcD6i5pkzKcy5AiSEU22xmj8MYkkPSaXVvbYo7Wx2hp6H",
-      "name": "go-libp2p-netutil",
-      "version": "0.4.18"
-    },
-    {
-      "author": "whyrusleeping",
-      "hash": "QmNgLg1NTw37iWbYPKcyK85YJ9Whs1MkPtJwhfqbNYAyKg",
-      "name": "go-libp2p-net",
-      "version": "3.0.22"
-    },
-    {
-      "author": "whyrusleeping",
-      "hash": "QmPiemjiKBC9VA7vZF82m4x1oygtg2c2YVqag8PX7dN1BD",
-      "name": "go-libp2p-peerstore",
-      "version": "2.0.13"
-    },
-    {
-      "author": "multiformats",
-      "hash": "QmNTCey11oxhb1AxDnQBRHtdhap6Ctud872NjAYPYYXPuc",
-      "name": "go-multiaddr",
-      "version": "1.4.0"
-    },
-    {
-      "author": "whyrusleeping",
-      "hash": "QmZNkThpqfVXs9GNbexPrfBbXSLNYeKrE7jwFM2oqHbyqN",
-      "name": "go-libp2p-protocol",
-      "version": "1.0.0"
-    },
-    {
-      "author": "whyrusleeping",
-      "hash": "QmWZnkipEJbsdUDhgTGBnKAN1iHM2WDMNqsXHyAuaAiCgo",
-      "name": "go-libp2p-loggables",
-      "version": "1.1.29"
-    },
-    {
-      "author": "why",
-      "hash": "QmSFo2QrMF4M1mKdB291ZqNtsie4NfwXCRdWgDU3inw4Ff",
-      "name": "go-libp2p-interface-connmgr",
-      "version": "0.0.27"
-    },
-    {
-      "hash": "QmTiRqrF5zkdZyrdsL5qndG1UbeWi8k8N2pYxCtXWrahR2",
-      "name": "go-libp2p-routing",
-      "version": "2.7.7"
-    },
-    {
-      "author": "jbenet",
-      "hash": "QmSJ9n2s9NUoA9D849W5jj5SJ94nMcZpj1jCgQJieiNqSt",
-      "name": "go-random",
-      "version": "1.0.0"
-    },
-    {
-      "author": "whyrusleeping",
-      "hash": "QmRL22E4paat7ky7vx9MLpR97JHHbFPrg3ytFQw6qp1y1s",
-      "name": "go-ipld-format",
-      "version": "0.8.0"
-    }
-  ],
-  "gxVersion": "0.0.1",
-  "language": "go",
-  "license": "",
-  "name": "go-graphsync",
-  "releaseCmd": "git commit -a -m \"gx publish $VERSION\"",
-  "version": "0.0.1"
-}
-

testbridge/mocknodes.go

+package testbridge
+
+import (
+	"fmt"
+
+	cid "github.com/ipfs/go-cid"
+	ipld "github.com/ipld/go-ipld-prime"
+)
+
+type mockSelectorSpec struct {
+	cidsVisited []cid.Cid
+}
+
+// NewMockSelectorSpec returns a new mock selector that will visit the given
+// cids.
+func NewMockSelectorSpec(cidsVisited []cid.Cid) ipld.Node {
+	return &mockSelectorSpec{cidsVisited}
+}
+
+func (mss *mockSelectorSpec) Kind() ipld.ReprKind { return ipld.ReprKind_Null }
+func (mss *mockSelectorSpec) TraverseField(key string) (ipld.Node, error) {
+	return nil, fmt.Errorf("404")
+}
+func (mss *mockSelectorSpec) TraverseIndex(idx int) (ipld.Node, error) {
+	return nil, fmt.Errorf("404")
+}
+func (mss *mockSelectorSpec) Keys() ipld.KeyIterator { return &mockKeyIterator{} }
+func (mss *mockSelectorSpec) KeysImmediate() ([]string, error) {
+	return nil, fmt.Errorf("404")
+}
+func (mss *mockSelectorSpec) Length() int               { return 0 }
+func (mss *mockSelectorSpec) IsNull() bool              { return true }
+func (mss *mockSelectorSpec) AsBool() (bool, error)     { return false, fmt.Errorf("404") }
+func (mss *mockSelectorSpec) AsInt() (int, error)       { return 0, fmt.Errorf("404") }
+func (mss *mockSelectorSpec) AsFloat() (float64, error) { return 0.0, fmt.Errorf("404") }
+func (mss *mockSelectorSpec) AsString() (string, error) { return "", fmt.Errorf("404") }
+func (mss *mockSelectorSpec) AsBytes() ([]byte, error)  { return nil, fmt.Errorf("404") }
+func (mss *mockSelectorSpec) AsLink() (cid.Cid, error)  { return cid.Cid{}, fmt.Errorf("404") }
+
+type mockKeyIterator struct {
+}
+
+func (mki *mockKeyIterator) Next() (string, error) { return "", fmt.Errorf("404") }
+func (mki *mockKeyIterator) HasNext() bool         { return false }
+
+type mockBlockNode struct {
+	data []byte
+}
+
+// NewMockBlockNode returns a new node for a byte array
+func NewMockBlockNode(data []byte) ipld.Node {
+	return &mockBlockNode{data}
+}
+
+func (mbn *mockBlockNode) Kind() ipld.ReprKind { return ipld.ReprKind_Bytes }
+func (mbn *mockBlockNode) TraverseField(key string) (ipld.Node, error) {
+	return nil, fmt.Errorf("404")
+}
+func (mbn *mockBlockNode) TraverseIndex(idx int) (ipld.Node, error) {
+	return nil, fmt.Errorf("404")
+}
+func (mbn *mockBlockNode) Keys() ipld.KeyIterator { return &mockKeyIterator{} }
+func (mbn *mockBlockNode) KeysImmediate() ([]string, error) {
+	return nil, fmt.Errorf("404")
+}
+func (mbn *mockBlockNode) Length() int               { return 0 }
+func (mbn *mockBlockNode) IsNull() bool              { return false }
+func (mbn *mockBlockNode) AsBool() (bool, error)     { return false, fmt.Errorf("404") }
+func (mbn *mockBlockNode) AsInt() (int, error)       { return 0, fmt.Errorf("404") }
+func (mbn *mockBlockNode) AsFloat() (float64, error) { return 0.0, fmt.Errorf("404") }
+func (mbn *mockBlockNode) AsString() (string, error) { return "", fmt.Errorf("404") }
+func (mbn *mockBlockNode) AsBytes() ([]byte, error)  { return mbn.data, nil }
+func (mbn *mockBlockNode) AsLink() (cid.Cid, error)  { return cid.Cid{}, fmt.Errorf("404") }

testbridge/mockselector.go

+package testbridge
+
+import (
+	"github.com/ipfs/go-cid"
+	ipldbridge "github.com/ipfs/go-graphsync/ipldbridge"
+	ipld "github.com/ipld/go-ipld-prime"
+)
+
+type mockSelector struct {
+	cidsVisited []cid.Cid
+}
+
+func newMockSelector(mss *mockSelectorSpec) ipldbridge.Selector {
+	return &mockSelector{mss.cidsVisited}
+}
+
+func (ms *mockSelector) Explore(ipld.Node) (ipld.KeyIterator, ipldbridge.Selector) {
+	return nil, ms
+}
+func (ms *mockSelector) Decide(ipld.Node) bool { return false }

testbridge/testbridge.go

+package testbridge
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+
+	cid "github.com/ipfs/go-cid"
+	ipldbridge "github.com/ipfs/go-graphsync/ipldbridge"
+	ipld "github.com/ipld/go-ipld-prime"
+	multihash "github.com/multiformats/go-multihash"
+)
+
+type mockIPLDBridge struct {
+}
+
+// NewMockIPLDBridge returns an IPLD bridge that works with MockSelectors
+func NewMockIPLDBridge() ipldbridge.IPLDBridge {
+	return &mockIPLDBridge{}
+}
+
+func (mb *mockIPLDBridge) ComposeLinkLoader(actualLoader ipldbridge.RawLoader) ipldbridge.LinkLoader {
+	return func(ctx context.Context, lnk cid.Cid, lnkCtx ipldbridge.LinkContext) (ipld.Node, error) {
+		r, err := actualLoader(ctx, lnk, lnkCtx)
+		if err != nil {
+			return nil, err
+		}
+		var buffer bytes.Buffer
+		io.Copy(&buffer, r)
+		data := buffer.Bytes()
+		hash, err := multihash.Sum(data, lnk.Prefix().MhType, lnk.Prefix().MhLength)
+		if err != nil {
+			return nil, err
+		}
+		if hash.B58String() != lnk.Hash().B58String() {
+			return nil, fmt.Errorf("hash mismatch")
+		}
+		return NewMockBlockNode(data), nil
+	}
+}
+
+func (mb *mockIPLDBridge) ValidateSelectorSpec(cidRootedSelector ipld.Node) []error {
+	_, ok := cidRootedSelector.(*mockSelectorSpec)
+	if !ok {
+		return []error{fmt.Errorf("not a selector")}
+	}
+	return nil
+}
+
+func (mb *mockIPLDBridge) EncodeNode(node ipld.Node) ([]byte, error) {
+	spec, ok := node.(*mockSelectorSpec)
+	if ok {
+		data, err := json.Marshal(spec.cidsVisited)
+		if err != nil {
+			return nil, err
+		}
+		return data, nil
+	}
+	return nil, fmt.Errorf("format not supported")
+}
+
+func (mb *mockIPLDBridge) DecodeNode(data []byte) (ipld.Node, error) {
+	var cidsVisited []cid.Cid
+	err := json.Unmarshal(data, &cidsVisited)
+	if err == nil {
+		return &mockSelectorSpec{cidsVisited}, nil
+	}
+	return nil, fmt.Errorf("format not supported")
+}
+
+func (mb *mockIPLDBridge) DecodeSelectorSpec(cidRootedSelector ipld.Node) (ipld.Node, ipldbridge.Selector, error) {
+	spec, ok := cidRootedSelector.(*mockSelectorSpec)
+	if !ok {
+		return nil, nil, fmt.Errorf("not a selector")
+	}
+	return nil, newMockSelector(spec), nil
+}
+
+func (mb *mockIPLDBridge) Traverse(ctx context.Context, loader ipldbridge.LinkLoader, root ipld.Node, s ipldbridge.Selector, fn ipldbridge.AdvVisitFn) error {
+	ms, ok := s.(*mockSelector)
+	if !ok {
+		return fmt.Errorf("not supported")
+	}
+	var lastErr error
+	for _, lnk := range ms.cidsVisited {
+		node, err := loader(ctx, lnk, ipldbridge.LinkContext{})
+		if err != nil {
+			lastErr = err
+		} else {
+			fn(ipldbridge.TraversalProgress{}, node, 0)
+		}
+	}
+	return lastErr
+}

testbridge/testbridge_test.go

+package testbridge
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"reflect"
+	"testing"
+
+	blocks "github.com/ipfs/go-block-format"
+
+	"github.com/ipld/go-ipld-prime"
+
+	"github.com/ipfs/go-cid"
+	"github.com/ipfs/go-graphsync/ipldbridge"
+	"github.com/ipfs/go-graphsync/testutil"
+)
+
+func TestSelectorTraversal(t *testing.T) {
+	blks := testutil.GenerateBlocksOfSize(5, 20)
+	cids := make([]cid.Cid, 0, 5)
+	for _, block := range blks {
+		cids = append(cids, block.Cid())
+	}
+	var uniqueBlocksVisited []blocks.Block
+	loader := func(ctx context.Context, lnk cid.Cid, lnkCtx ipldbridge.LinkContext) (io.Reader, error) {
+		for _, block := range blks {
+			if block.Cid() == lnk {
+				if testutil.ContainsBlock(uniqueBlocksVisited, block) {
+					return nil, fmt.Errorf("loaded block twice")
+				}
+				uniqueBlocksVisited = append(uniqueBlocksVisited, block)
+				return bytes.NewReader(block.RawData()), nil
+			}
+		}
+		return nil, fmt.Errorf("unable to load block")
+	}
+	bridge := NewMockIPLDBridge()
+	linkloader := bridge.ComposeLinkLoader(loader)
+	mockSelectorSpec := NewMockSelectorSpec(cids)
+	node, selector, err := bridge.DecodeSelectorSpec(mockSelectorSpec)
+	if err != nil {
+		t.Fatal("unable to decode selector")
+	}
+	var traversalFn ipldbridge.AdvVisitFn
+	traversalFn = func(tp ipldbridge.TraversalProgress, node ipld.Node, traversalReason ipldbridge.TraversalReason) error {
+		return nil
+	}
+	ctx := context.Background()
+	err = bridge.Traverse(ctx, linkloader, node, selector, traversalFn)
+	if err != nil {
+		t.Fatal(err.Error())
+	}
+	if len(uniqueBlocksVisited) != 5 {
+		t.Fatal("did not visit all blocks")
+	}
+}
+
+func TestEncodeDecodeSelectorSpec(t *testing.T) {
+	cids := testutil.GenerateCids(5)
+	spec := NewMockSelectorSpec(cids)
+	bridge := NewMockIPLDBridge()
+	data, err := bridge.EncodeNode(spec)
+	if err != nil {
+		t.Fatal("error encoding selector spec")
+	}
+	node, err := bridge.DecodeNode(data)
+	if err != nil {
+		t.Fatal("error decoding data")
+	}
+	returnedSpec, ok := node.(*mockSelectorSpec)
+	if !ok {
+		t.Fatal("did not decode a selector")
+	}
+	if len(returnedSpec.cidsVisited) != 5 {
+		t.Fatal("did not decode enough cids")
+	}
+	if !reflect.DeepEqual(cids, returnedSpec.cidsVisited) {
+		t.Fatal("did not decode correct cids")
+	}
+}