client,step1: add a KS compatible client, and a script to package tokens for PC step1

toolkit/client/requester_infura.go

@@ -0,0 +1,90 @@
+package client
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"iter"
+	"net/http"
+	"net/url"
+
+	"github.com/ucan-wg/go-ucan/did"
+	"github.com/ucan-wg/go-ucan/pkg/command"
+	"github.com/ucan-wg/go-ucan/token/delegation"
+)
+
+var _ DelegationRequester = &InfuraRequester{}
+
+type InfuraRequester struct {
+	baseURL string
+}
+
+// dev: http://ucan-issuer-api.commercial-dev.eks-dev.infura.org/
+// prod:
+func NewInfuraRequester(baseURL string) *InfuraRequester {
+	return &InfuraRequester{baseURL: baseURL}
+}
+
+func (i InfuraRequester) RequestDelegation(ctx context.Context, audience did.DID, cmd command.Command, subject did.DID) (iter.Seq2[*delegation.Bundle, error], error) {
+	p, err := url.JoinPath(i.baseURL, "v1/token/generate-with-did")
+	if err != nil {
+		return nil, err
+	}
+
+	payload := struct {
+		Cmd string `json:"cmd"`
+		Aud string `json:"aud"`
+	}{
+		Cmd: cmd.String(),
+		Aud: audience.String(),
+	}
+
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return nil, err
+	}
+
+	r, err := http.NewRequest(http.MethodPost, p, bytes.NewReader(body))
+	if err != nil {
+		return nil, err
+	}
+
+	res, err := http.DefaultClient.Do(r.WithContext(ctx))
+	if err != nil {
+		return nil, err
+	}
+
+	resp := struct {
+		Cid     string `json:"cid"`
+		Content string `json:"content"`
+	}{}
+	if err := json.NewDecoder(res.Body).Decode(&resp); err != nil {
+		return nil, err
+	}
+
+	raw, err := base64.StdEncoding.DecodeString(resp.Content)
+	if err != nil {
+		return nil, err
+	}
+
+	tkn, c, err := delegation.FromSealed(raw)
+	if err != nil {
+		return nil, err
+	}
+
+	// For sanity, we verify that the delegation we got matches the expected subject,
+	// meaning that we are talking to the expected issuer.
+	if tkn.Subject() != subject {
+		return nil, fmt.Errorf("received token has unexpected subject: expected %s, got %s", subject, tkn.Subject())
+	}
+
+	return func(yield func(*delegation.Bundle, error) bool) {
+		yield(&delegation.Bundle{
+			Cid:     c,
+			Decoded: tkn,
+			Sealed:  raw,
+		}, nil)
+	}, nil
+}