feat: Credential VC Id is an URN and not a url (#680)

* feat: Return credential ID as URN

* chore: linter

* chore: Clearest implementation of urn package.

internal/core/services/claims.go

@@ -32,6 +32,7 @@ import (
 	"github.com/polygonid/sh-id-platform/internal/loader"
 	"github.com/polygonid/sh-id-platform/internal/log"
 	"github.com/polygonid/sh-id-platform/internal/repositories"
+	"github.com/polygonid/sh-id-platform/internal/urn"
 	"github.com/polygonid/sh-id-platform/pkg/credentials/revocation_status"
 	"github.com/polygonid/sh-id-platform/pkg/pubsub"
 	"github.com/polygonid/sh-id-platform/pkg/rand"
@@ -652,10 +653,13 @@ func (c *claim) getAgentCredential(ctx context.Context, basicMessage *ports.Agen
 		return nil, fmt.Errorf("invalid credential fetch request body: %w", err)
 	}
 
-	claimID, err := uuid.Parse(fetchRequestBody.ID)
+	claimID, err := urn.UUIDFromURNString(fetchRequestBody.ID)
 	if err != nil {
-		log.Error(ctx, "wrong claimID in agent request body", "err", err)
-		return nil, fmt.Errorf("invalid claim ID")
+		claimID, err = uuid.Parse(fetchRequestBody.ID)
+		if err != nil {
+			log.Error(ctx, "wrong claimID in agent request body", "err", err)
+			return nil, fmt.Errorf("invalid claim ID")
+		}
 	}
 
 	claim, err := c.icRepo.GetByIdAndIssuer(ctx, c.storage.Pgx, basicMessage.IssuerDID, claimID)
@@ -802,7 +806,7 @@ func (c *claim) newVerifiableCredential(ctx context.Context, claimReq *ports.Cre
 
 	issuanceDate := time.Now().UTC()
 	return verifiable.W3CCredential{
-		ID:                c.buildCredentialID(*claimReq.DID, vcID, claimReq.SingleIssuer),
+		ID:                string(c.buildCredentialID(vcID)),
 		Context:           credentialCtx,
 		Type:              credentialType,
 		Expiration:        claimReq.Expiration,
@@ -819,10 +823,6 @@ func (c *claim) newVerifiableCredential(ctx context.Context, claimReq *ports.Cre
 	}, nil
 }
 
-func (c *claim) buildCredentialID(issuerDID w3c.DID, credID uuid.UUID, singleIssuer bool) string {
-	// TODO: review how to build the credential ID
-	if singleIssuer {
-		return fmt.Sprintf("%s/v1/credentials/%s", strings.TrimSuffix(c.host, "/"), credID.String())
-	}
-	return fmt.Sprintf("%s/v1/%s/claims/%s", strings.TrimSuffix(c.host, "/"), issuerDID.String(), credID.String())
+func (c *claim) buildCredentialID(credID uuid.UUID) urn.URN {
+	return urn.FromUUID(credID)
 }

internal/urn/urn.go

@@ -0,0 +1,50 @@
+package urn
+
+import (
+	"errors"
+
+	"github.com/google/uuid"
+)
+
+// URN represents a Uniform Resource Name.
+type URN string
+
+// FromUUID creates a URN from a UUID.
+func FromUUID(uuid uuid.UUID) URN {
+	return URN("urn:uuid:" + uuid.String())
+}
+
+// UUID returns the UUID from a URN. It can throw an error to prevent bad constructor calls or urns without uuids
+func (u URN) UUID() (uuid.UUID, error) {
+	if err := u.valid(); err != nil {
+		return uuid.Nil, err
+	}
+	return uuid.Parse(string(u[9:]))
+}
+
+func (u URN) valid() error {
+	if len(u) < len("urn:uuid:") {
+		return errors.New("invalid uuid URN length")
+	}
+	if u[:9] != "urn:uuid:" {
+		return errors.New("invalid uuid URN prefix")
+	}
+	return nil
+}
+
+// Parse creates a URN from a string.
+func Parse(u string) (URN, error) {
+	if err := URN(u).valid(); err != nil {
+		return "", err
+	}
+	return URN(u), nil
+}
+
+// UUIDFromURNString returns the UUID from a URN string.
+func UUIDFromURNString(s string) (uuid.UUID, error) {
+	urn, err := Parse(s)
+	if err != nil {
+		return uuid.Nil, err
+	}
+	return urn.UUID()
+}

internal/urn/urn_test.go

@@ -0,0 +1,36 @@
+package urn
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFromUUID(t *testing.T) {
+	id := uuid.New()
+	urn := FromUUID(id)
+	assert.Equal(t, "urn:uuid:"+id.String(), string(urn))
+}
+
+func TestUUIDFromURNString(t *testing.T) {
+	for _, ts := range []struct {
+		urn string
+		err error
+	}{
+		{"", errors.New("invalid uuid URN length")},
+		{"urn:uuid:", errors.New("invalid UUID length: 0")},
+		{"urn:uuid:1234", errors.New("invalid UUID length: 4")},
+		{"urn:uuid:123e4567-e89b-12d3-a456-426614174000", nil},
+	} {
+		t.Run(ts.urn, func(t *testing.T) {
+			u, err := UUIDFromURNString(ts.urn)
+			if err == nil {
+				assert.Equal(t, ts.urn[9:], u.String())
+			} else {
+				assert.Equal(t, ts.err.Error(), err.Error())
+			}
+		})
+	}
+}