use UCAN tokens for NFT marketplace

scripts/generateNftServiceKeypair.js

@@ -0,0 +1,89 @@
+import { KeyPair } from 'ucan-storage/keypair';
+import { build } from 'ucan-storage/ucan-storage';
+
+const SERVICE_ENDPOINT = 'https://api.nft.storage'; // default
+const API_TOKEN = process.env.API_KEY;
+
+/**
+ * Obtaining the service DID
+ *
+ */
+async function getServiceDid() {
+  const didRes = await fetch(new URL('/did', SERVICE_ENDPOINT));
+  const { ok, value: serviceDid } = await didRes.json();
+
+  if (ok) {
+    return serviceDid;
+  } else {
+    throw new Error('Could not get Service DID');
+  }
+}
+
+/**
+ * Obtaining a root UCAN token.
+ * It will be valid for a duration of two weeks
+ *
+ */
+async function getRootToken(token) {
+  const ucanReq = await fetch(new URL('/ucan/token', SERVICE_ENDPOINT), {
+    method: 'POST',
+    headers: {
+      Authorization: `Bearer ${token}`,
+    },
+  });
+
+  if (!ucanReq.ok) {
+    throw new Error('Failed to get root UCAN token');
+  }
+
+  const { value: rootUCAN } = await ucanReq.json();
+
+  return rootUCAN;
+}
+
+/**
+ * Obtaining UCAN token with specified expiration date (10 days)
+ *
+ */
+async function getUCAN(kp, serviceDid, rootUCAN) {
+  // convert timestamp to seconds
+  const nowInSeconds = Math.floor(Date.now() / 1000);
+  const expiration = nowInSeconds + 864000; // 10 days from now
+
+  try {
+    return await build({
+      issuer: kp,
+      audience: serviceDid,
+      expiration: expiration,
+      capabilities: [
+        {
+          with: `storage://${kp.did()}`,
+          can: 'upload/*',
+        },
+      ],
+      proofs: [rootUCAN],
+    });
+  } catch (error) {
+    throw new Error('Could not create UCAN token:', error);
+  }
+}
+
+async function main() {
+  const pair = await KeyPair.create();
+  const privateKey = pair.export();
+
+  const kp = await KeyPair.fromExportedKey(privateKey);
+
+  const serviceDid = await getServiceDid();
+
+  const rootUCAN = await getRootToken(API_TOKEN);
+
+  const ucan = await getUCAN(kp, serviceDid, rootUCAN);
+
+  process.stdout.write(`{
+    marketplaceDid: ${kp.did()},
+    ucan: ${ucan}
+  }\n`);
+}
+
+main().catch((error) => console.error(error));