From 870b05f1b1d967b811cb73f7f3e2112c2e7314c9 Mon Sep 17 00:00:00 2001
From: Alan Shaw <alan@storacha.network>
Date: Tue, 22 Oct 2024 13:21:25 +0100
Subject: [PATCH] feat: add delegation format and parse utility functions

---
 core/delegation/delegation.go      | 36 ++++++++++++++++++++++++++++++
 core/delegation/delegation_test.go | 22 ++++++++++++++++++
 go.mod                             |  1 +
 3 files changed, 59 insertions(+)

diff --git a/core/delegation/delegation.go b/core/delegation/delegation.go
index 32e9c33..9f8f6e9 100644
--- a/core/delegation/delegation.go
+++ b/core/delegation/delegation.go
@@ -7,6 +7,10 @@ import (
 	"iter"
 	"sync"
 
+	"github.com/ipfs/go-cid"
+	"github.com/multiformats/go-multibase"
+	"github.com/multiformats/go-multicodec"
+	"github.com/multiformats/go-multihash"
 	"github.com/storacha/go-ucanto/core/car"
 	"github.com/storacha/go-ucanto/core/dag/blockstore"
 	adm "github.com/storacha/go-ucanto/core/delegation/datamodel"
@@ -206,3 +210,35 @@ func Extract(b []byte) (Delegation, error) {
 
 	return NewDelegationView(model.Ucan0_9_1, br)
 }
+
+func Format(dlg Delegation) (string, error) {
+	bytes, err := io.ReadAll(dlg.Archive())
+	if err != nil {
+		return "", fmt.Errorf("archiving delegation: %w", err)
+	}
+	digest, err := multihash.Sum(bytes, uint64(multicodec.Identity), -1)
+	if err != nil {
+		return "", fmt.Errorf("creating multihash: %w", err)
+	}
+	return cid.NewCidV1(uint64(multicodec.Car), digest).StringOfBase(multibase.Base64pad)
+}
+
+func Parse(input string) (Delegation, error) {
+	cid, err := cid.Decode(input)
+	if err != nil {
+		return nil, fmt.Errorf("decoding CID: %w", err)
+	}
+	codec := multicodec.Code(cid.Prefix().Codec)
+	if codec != multicodec.Car {
+		return nil, fmt.Errorf("non CAR codec found: %s", codec.String())
+	}
+	mhinfo, err := multihash.Decode(cid.Hash())
+	if err != nil {
+		return nil, fmt.Errorf("decoding multihash: %w", err)
+	}
+	mhcodec := multicodec.Code(mhinfo.Code)
+	if mhcodec != multicodec.Identity {
+		return nil, fmt.Errorf("non identity multihash: %s", mhcodec.String())
+	}
+	return Extract(mhinfo.Digest)
+}
diff --git a/core/delegation/delegation_test.go b/core/delegation/delegation_test.go
index c577f7c..451ad45 100644
--- a/core/delegation/delegation_test.go
+++ b/core/delegation/delegation_test.go
@@ -1,6 +1,7 @@
 package delegation
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/storacha/go-ucanto/core/ipld/block"
@@ -34,3 +35,24 @@ func TestAttach(t *testing.T) {
 	}
 	require.True(t, found)
 }
+
+func TestFormatParse(t *testing.T) {
+	dlg, err := Delegate(
+		fixtures.Alice,
+		fixtures.Bob,
+		[]ucan.Capability[ucan.NoCaveats]{
+			ucan.NewCapability("test/proof", fixtures.Alice.DID().String(), ucan.NoCaveats{}),
+		},
+	)
+	require.NoError(t, err)
+
+	formatted, err := Format(dlg)
+	require.NoError(t, err)
+
+	fmt.Println(formatted)
+
+	parsed, err := Parse(formatted)
+	require.NoError(t, err)
+
+	require.Equal(t, dlg.Link(), parsed.Link())
+}
diff --git a/go.mod b/go.mod
index 0a144e7..bfc454a 100644
--- a/go.mod
+++ b/go.mod
@@ -9,6 +9,7 @@ require (
 	github.com/ipld/go-ipld-prime v0.21.1-0.20240917223228-6148356a4c2e
 	github.com/multiformats/go-base32 v0.1.0
 	github.com/multiformats/go-multibase v0.2.0
+	github.com/multiformats/go-multicodec v0.9.0
 	github.com/multiformats/go-multihash v0.2.3
 	github.com/multiformats/go-varint v0.0.7
 	github.com/pkg/errors v0.9.1