fix: Switch to a class setup for the core methods

lib/sdk.js

@@ -57,21 +57,34 @@ export.exportKey = (key) => {
 }
 
 /**
- * Generate a ticket for the required epoch.
- *
- * @param key {CryptoKey}
- * @param timestamp {Number}
- *
- * @returns {Number}
+ * Class holding the core functionality of the Pat SDK
  */
-export.createTicket = (key, timestamp) => {
-  // An ArrayBuffer representation of the timestamp
-  const _timestamp = (new TextEncoder()).encode(timestamp).buffer
+export.PatSDK = class PatSDK {
+  /**
+   * Create an instance of the Pat SDK.
+   *
+   * @param key {CryptoKey}
+   */
+  constructor(key) {
+    this.key = key
+  }
+
+  /**
+   * Generate a ticket for the required epoch.
+   *
+   * @param timestamp {Number}
+   *
+   * @returns {Number}
+   */
+  createTicket(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
+    return crypto.subtle.sign(keyOptions[0], this.key, _timestamp).then((hash) => {
+      return (new Uint8Array(hash)).reduce((acc, int) => {
+        return (acc + int) % 1000
+      })
     })
-  })
+  }
 }