syntax: more AtIdentifier helpers and test coverage

atproto/syntax/atidentifier.go

@@ -24,6 +24,11 @@ func ParseAtIdentifier(raw string) (*AtIdentifier, error) {
 	return &AtIdentifier{Inner: handle}, nil
 }
 
+func (n AtIdentifier) IsHandle() bool {
+	_, ok := n.Inner.(Handle)
+	return ok
+}
+
 func (n AtIdentifier) AsHandle() (Handle, error) {
 	handle, ok := n.Inner.(Handle)
 	if ok {
@@ -32,6 +37,11 @@ func (n AtIdentifier) AsHandle() (Handle, error) {
 	return "", fmt.Errorf("AT Identifier is not a Handle")
 }
 
+func (n AtIdentifier) IsDID() bool {
+	_, ok := n.Inner.(DID)
+	return ok
+}
+
 func (n AtIdentifier) AsDID() (DID, error) {
 	did, ok := n.Inner.(DID)
 	if ok {

atproto/syntax/atidentifier_test.go

@@ -48,3 +48,38 @@ func TestInteropAtIdentifiersInvalid(t *testing.T) {
 	}
 	assert.NoError(scanner.Err())
 }
+
+func TestDowncase(t *testing.T) {
+	assert := assert.New(t)
+
+	aidh, err := ParseAtIdentifier("example.com")
+	assert.NoError(err)
+	assert.True(aidh.IsHandle())
+	assert.False(aidh.IsDID())
+	_, err = aidh.AsHandle()
+	assert.NoError(err)
+	_, err = aidh.AsDID()
+	assert.Error(err)
+
+	aidd, err := ParseAtIdentifier("did:web:example.com")
+	assert.NoError(err)
+	assert.False(aidd.IsHandle())
+	assert.True(aidd.IsDID())
+	_, err = aidd.AsHandle()
+	assert.Error(err)
+	_, err = aidd.AsDID()
+	assert.NoError(err)
+}
+
+func TestEmtpy(t *testing.T) {
+	assert := assert.New(t)
+
+	atid := AtIdentifier{}
+
+	assert.False(atid.IsHandle())
+	assert.False(atid.IsDID())
+	assert.Equal(atid, atid.Normalize())
+	atid.AsHandle()
+	atid.AsDID()
+	assert.Empty(atid.String())
+}