add an early version of a UCAN client

toolkit/client/client.go

@@ -0,0 +1,78 @@
+package client
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/ipfs/go-cid"
+	"github.com/libp2p/go-libp2p/core/crypto"
+	"github.com/ucan-wg/go-ucan/did"
+	"github.com/ucan-wg/go-ucan/pkg/command"
+	"github.com/ucan-wg/go-ucan/pkg/container"
+	"github.com/ucan-wg/go-ucan/token/invocation"
+)
+
+type Client struct {
+	did     did.DID
+	privKey crypto.PrivKey
+
+	pool      *Pool
+	requester DelegationRequester
+}
+
+func NewClient(privKey crypto.PrivKey, requester DelegationRequester) (*Client, error) {
+	d, err := did.FromPrivKey(privKey)
+	if err != nil {
+		return nil, err
+	}
+	return &Client{
+		did:       d,
+		privKey:   privKey,
+		pool:      NewPool(),
+		requester: requester,
+	}, nil
+}
+
+// PrepareInvoke returns an invocation and the proof delegation, bundled in a container.Writer.
+func (c *Client) PrepareInvoke(ctx context.Context, cmd command.Command, subject did.DID, opts ...invocation.Option) (container.Writer, error) {
+	var proof []cid.Cid
+
+	// do we already have a valid proof?
+	if proof = c.pool.FindProof(cmd, c.did, subject); len(proof) == 0 {
+		// we need to request a new proof
+		proofBundles, err := c.requester.RequestDelegation(ctx, cmd, c.did, subject)
+		if err != nil {
+			return nil, fmt.Errorf("requesting delegation: %w", err)
+		}
+
+		// cache the new proofs
+		for bundle, err := range proofBundles {
+			if err != nil {
+				return nil, err
+			}
+			proof = append(proof, bundle.Cid)
+			c.pool.AddBundle(bundle)
+		}
+	}
+
+	inv, err := invocation.New(c.did, subject, cmd, proof, opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	invSealed, invCid, err := inv.ToSealed(c.privKey)
+	if err != nil {
+		return nil, err
+	}
+
+	cont := container.NewWriter()
+	cont.AddSealed(invCid, invSealed)
+	for bundle, err := range c.pool.GetBundles(proof) {
+		if err != nil {
+			return nil, err
+		}
+		cont.AddSealed(bundle.Cid, bundle.Sealed)
+	}
+
+	return cont, nil
+}