From 78838e451827203860d4eabc91ee90d2354e42b9 Mon Sep 17 00:00:00 2001
From: Alan Shaw <alan.shaw@protocol.ai>
Date: Tue, 19 Sep 2023 22:52:23 +0100
Subject: [PATCH] feat: support for non did:key

---
 did.go      | 19 ++++++++++++++++---
 did_test.go | 26 ++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/did.go b/did.go
index b093ce4..2c49953 100644
--- a/did.go
+++ b/did.go
@@ -11,9 +11,13 @@ import (
 const Prefix = "did:"
 const KeyPrefix = "did:key:"
 
+const DIDCore = 0x0d1d
 const Ed25519 = 0xed
 
+var MethodOffset = varint.UvarintSize(uint64(DIDCore))
+
 type DID struct {
+	key bool
 	str string
 }
 
@@ -37,8 +41,11 @@ func (d DID) DID() DID {
 }
 
 func (d DID) String() string {
-	key, _ := mbase.Encode(mbase.Base58BTC, []byte(d.str))
-	return "did:key:" + key
+	if d.key {
+		key, _ := mbase.Encode(mbase.Base58BTC, []byte(d.str))
+		return "did:key:" + key
+	}
+	return "did:" + d.str[MethodOffset:]
 }
 
 func Decode(bytes []byte) (DID, error) {
@@ -47,6 +54,8 @@ func Decode(bytes []byte) (DID, error) {
 		return Undef, err
 	}
 	if code == Ed25519 {
+		return DID{str: string(bytes), key: true}, nil
+	} else if code == DIDCore {
 		return DID{str: string(bytes)}, nil
 	}
 	return Undef, fmt.Errorf("decoding DID: unsupported DID encoding: 0x%x", code)
@@ -68,5 +77,9 @@ func Parse(str string) (DID, error) {
 		return Decode(bytes)
 	}
 
-	return Undef, fmt.Errorf("parsing DID: unsupported method")
+	buf := make([]byte, MethodOffset)
+	varint.PutUvarint(buf, DIDCore)
+	suffix, _ := strings.CutPrefix(str, Prefix)
+	buf = append(buf, suffix...)
+	return DID{str: string(buf)}, nil
 }
diff --git a/did_test.go b/did_test.go
index 720e733..47cfe96 100644
--- a/did_test.go
+++ b/did_test.go
@@ -30,6 +30,32 @@ func TestDecodeDIDKey(t *testing.T) {
 	}
 }
 
+func TestParseDIDWeb(t *testing.T) {
+	str := "did:web:up.web3.storage"
+	d, err := Parse(str)
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+	if d.String() != str {
+		t.Fatalf("expected %v to equal %v", d.String(), str)
+	}
+}
+
+func TestDecodeDIDWeb(t *testing.T) {
+	str := "did:web:up.web3.storage"
+	d0, err := Parse(str)
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+	d1, err := Decode(d0.Bytes())
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+	if d1.String() != str {
+		t.Fatalf("expected %v to equal %v", d1.String(), str)
+	}
+}
+
 func TestEquivalence(t *testing.T) {
 	u0 := DID{}
 	u1 := Undef