feat: Add the first few functions to the SDK

lib/sdk.js

@@ -0,0 +1,61 @@
+'use strict'
+
+const keyOptions = [
+  {
+    name: 'HMAC',
+    hash: { name: 'SHA-256' }
+  },
+  true,
+  ['sign']
+]
+
+/**
+ * Create a new `CryptoKey` object that can be used to sign values.
+ *
+ * @returns {CryptoKey}
+ */
+export.generateKey = () => {
+  return crypto.subtle.generateKey(...keyOptions)
+}
+
+/**
+ * Import an `ArrayBuffer` object as a raw key and convert it into a usable `CryptoKey`.
+ *
+ * @param key {ArrayBuffer}
+ *
+ * @returns {CryptoKey}
+ */
+export.importKey = (key) => {
+  return crypto.subtle.importKey('raw', key, ...keyOptions)
+}
+
+/**
+ * Export the provided `CryptoKey` and convert it into an `ArrayBuffer` object.
+ *
+ * @param key {CryptoKey}
+ *
+ * @returns {ArrayBuffer}
+ */
+export.exportKey = (key) => {
+  return crypto.subtle.exportKey('raw', key)
+}
+
+/**
+ * Generate a ticket for the required epoch.
+ *
+ * @param key {CryptoKey}
+ * @param timestamp {Number}
+ *
+ * @returns {Number}
+ */
+export.createTicket = (key, timestamp) => {
+  // An ArrayBuffer representation of the timestamp
+  const _timestamp = (new TextEncoder()).encode(timestamp).buffer
+
+  return crypto.subtle.sign(keyOptions[0], key, _timestamp).then((key) => {
+    return (new Uint8Array(key)).reduce((acc, int) => {
+      return (acc + int) % 1000
+    })
+  })
+}
+