feat(utils): add pkce utils

packages/@vssue/utils/src/pkce.ts

@@ -0,0 +1,38 @@
+// https://www.oauth.com/playground/authorization-code-with-pkce.html
+
+/**
+ * Step 1 - 1
+ *
+ * Generate code verifier
+ */
+const generateCodeVerifier = (length: number = 43): string => {
+  let len: number = length
+  if (len < 43) len = 43
+  if (len > 128) len = 128
+
+  const randomArr = window.crypto.getRandomValues(new Uint8Array(len))
+  const validChars =
+    'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~'
+
+  let codeVerifier = ''
+
+  for (const i of randomArr) {
+    codeVerifier += validChars[i % len]
+  }
+
+  return codeVerifier
+}
+
+/**
+ * Step 1 -2
+ *
+ * Generate code challenge
+ */
+const generateCodeChallenge = async (codeVerifier: string): Promise<string> => {
+  const data = new TextEncoder().encode(codeVerifier)
+  const hash = await crypto.subtle.digest('SHA-256', data)
+  return btoa(String.fromCharCode(...new Uint8Array(hash)))
+    .replace(/\+/g, '-')
+    .replace(/\//g, '_')
+    .replace(/=+$/, '')
+}