token: add invocation partial stub

token/invocation/schema.go

@@ -0,0 +1,77 @@
+package invocation
+
+import (
+	_ "embed"
+	"fmt"
+	"sync"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/node/bindnode"
+	"github.com/ipld/go-ipld-prime/schema"
+
+	"github.com/ucan-wg/go-ucan/pkg/meta"
+	"github.com/ucan-wg/go-ucan/token/internal/envelope"
+)
+
+// [Tag] is the string used as a key within the SigPayload that identifies
+// that the TokenPayload is an invocation.
+//
+// [Tag]: https://github.com/ucan-wg/invocation#type-tag
+const Tag = "ucan/inv@1.0.0-rc.1"
+
+//go:embed invocation.ipldsch
+var schemaBytes []byte
+
+var (
+	once sync.Once
+	ts   *schema.TypeSystem
+	err  error
+)
+
+func mustLoadSchema() *schema.TypeSystem {
+	once.Do(func() {
+		ts, err = ipld.LoadSchemaBytes(schemaBytes)
+	})
+	if err != nil {
+		panic(fmt.Errorf("failed to load IPLD schema: %s", err))
+	}
+	return ts
+}
+
+func payloadType() schema.Type {
+	return mustLoadSchema().TypeByName("Payload")
+}
+
+var _ envelope.Tokener = (*tokenPayloadModel)(nil)
+
+// TODO
+type tokenPayloadModel struct {
+	// Issuer DID (sender)
+	Iss string
+	// Audience DID (receiver)
+	Aud string
+	// Principal that the chain is about (the Subject)
+	// optional: can be nil
+	Sub *string
+
+	// The Command to eventually invoke
+	Cmd string
+
+	// A unique, random nonce
+	Nonce []byte
+
+	// Arbitrary Metadata
+	Meta meta.Meta
+
+	// The timestamp at which the Invocation becomes invalid
+	// optional: can be nil
+	Exp *int64
+}
+
+func (e *tokenPayloadModel) Prototype() schema.TypedPrototype {
+	return bindnode.Prototype((*tokenPayloadModel)(nil), payloadType())
+}
+
+func (*tokenPayloadModel) Tag() string {
+	return Tag
+}