add validFrom and validUntil aliases for issuanceDate and epirationDate

vc/vc.go

@@ -138,10 +138,18 @@ type VerifiableCredential struct {
 	Type []ssi.URI `json:"type"`
 	// Issuer refers to the party that issued the credential
 	Issuer ssi.URI `json:"issuer"`
-	// IssuanceDate is a rfc3339 formatted datetime.
+	// IssuanceDate is a rfc3339 formatted datetime. Has alias ValidFrom
 	IssuanceDate time.Time `json:"issuanceDate"`
-	// ExpirationDate is a rfc3339 formatted datetime. It is optional
+	// ValidFrom is a rfc3339 formatted datetime. It is optional, and is mutually exclusive with IssuanceDate (not enforced).
+	// It's a forwards compatible alternative for IssuanceDate.
+	// The jwt-vc 'nbf' field will unmarshal to IssuanceDate, which may not match with the JSON-LD definition of certain VCs.
+	ValidFrom *time.Time `json:"validFrom,omitempty"`
+	// ExpirationDate is a rfc3339 formatted datetime. Has alias ValidUntil. It is optional
 	ExpirationDate *time.Time `json:"expirationDate,omitempty"`
+	// ValidFrom is a rfc3339 formatted datetime. It is optional, and is mutually exclusive with ExpirationDate (not enforced).
+	// It's a forwards compatible alternative for ExpirationDate.
+	// The jwt-vc 'exp' field will unmarshal to ExpirationDate, which may not match with the JSON-LD definition of certain VCs.
+	ValidUntil *time.Time `json:"validUntil,omitempty"`
 	// CredentialStatus holds information on how the credential can be revoked. It is optional
 	CredentialStatus *CredentialStatus `json:"credentialStatus,omitempty"`
 	// CredentialSubject holds the actual data for the credential. It must be extracted using the UnmarshalCredentialSubject method and a custom type.
@@ -173,6 +181,32 @@ func (vc VerifiableCredential) JWT() jwt.Token {
 	return token
 }
 
+// ValidAt returns true if
+// - t >= IssuanceDate and ValidFrom
+// - t <= ExpirationDate and ValidUntil
+// For any value that is missing, the evaluation defaults to true
+func (vc VerifiableCredential) ValidAt(t time.Time) bool {
+	// IssuanceDate is a required field, but will default to the zero value when missing. (when ValidFrom != nil)
+	// t > IssuanceDate
+	if !vc.IssuanceDate.IsZero() && t.Before(vc.IssuanceDate) {
+		return false
+	}
+	// t > ValidFrom
+	if vc.ValidFrom != nil && t.Before(*vc.ValidFrom) {
+		return false
+	}
+	// t < ExpirationDate
+	if vc.ExpirationDate != nil && t.After(*vc.ExpirationDate) {
+		return false
+	}
+	// t < ValidUntil
+	if vc.ValidUntil != nil && t.After(*vc.ValidUntil) {
+		return false
+	}
+	// valid
+	return true
+}
+
 // CredentialStatus defines the method on how to determine a credential is revoked.
 type CredentialStatus struct {
 	ID   ssi.URI `json:"id"`

vc/vc_test.go

@@ -379,3 +379,21 @@ func TestCreateJWTVerifiableCredential(t *testing.T) {
 		assert.Nil(t, claims[jwt.JwtIDKey])
 	})
 }
+
+func TestVerifiableCredential_ValidAt(t *testing.T) {
+	lll := time.Date(1999, 0, 0, 0, 0, 0, 0, time.UTC)
+	hhh := time.Date(2001, 0, 0, 0, 0, 0, 0, time.UTC)
+
+	// no validity period is always true; includes missing IssuanceDate(.IsZero() == true)
+	assert.True(t, VerifiableCredential{}.ValidAt(time.Now()))
+
+	// valid on bounds
+	assert.True(t, VerifiableCredential{IssuanceDate: lll, ValidFrom: &lll}.ValidAt(lll))
+	assert.True(t, VerifiableCredential{ExpirationDate: &lll, ValidUntil: &lll}.ValidAt(lll))
+
+	// invalid
+	assert.False(t, VerifiableCredential{IssuanceDate: hhh, ValidFrom: &lll}.ValidAt(lll))
+	assert.False(t, VerifiableCredential{IssuanceDate: lll, ValidFrom: &hhh}.ValidAt(lll))
+	assert.False(t, VerifiableCredential{ExpirationDate: &hhh, ValidUntil: &lll}.ValidAt(hhh))
+	assert.False(t, VerifiableCredential{ExpirationDate: &lll, ValidUntil: &hhh}.ValidAt(hhh))
+}