fix: 애플로그인 오류 처리

KeKi/Scenes/Login/LoginViewController.swift

@@ -158,14 +158,14 @@ extension LoginViewController: ASAuthorizationControllerDelegate, ASAuthorizatio
     func authorizationController(controller: ASAuthorizationController, didCompleteWithAuthorization authorization: ASAuthorization) {
         guard let appleIDCredential = authorization.credential as? ASAuthorizationAppleIDCredential else { return }
 
-        if let email = UserDefaults.standard.value(forKey: "appleEmail") {
-            requestSocialLogin(email: email as! String, provider: "애플")
-
-        } else if let email = appleIDCredential.email {
-            UserDefaults.standard.set(email, forKey: "appleEmail")
+        if let email = appleIDCredential.email { // 2번째 애플 로그인부터는 email이 identityToken에 들어있음.
             requestSocialLogin(email: email, provider: "애플")
+        } else {
+            if let tokenString = String(data: appleIDCredential.identityToken ?? Data(), encoding: .utf8) {
+                let email = decode(jwtToken: tokenString)["email"] as? String ?? ""
+                requestSocialLogin(email: email, provider: "애플")
+            }
         }
-
     }
 
     func authorizationController(controller: ASAuthorizationController, didCompleteWithError error: Error) {
@@ -175,6 +175,36 @@ extension LoginViewController: ASAuthorizationControllerDelegate, ASAuthorizatio
     func presentationAnchor(for controller: ASAuthorizationController) -> ASPresentationAnchor {
         return self.view.window!
     }
+
+    // (두번째 이후부터의 애플로그인을 위한 메소드) JWTToken -> dictionary
+    private func decode(jwtToken jwt: String) -> [String: Any] {
+
+        func base64UrlDecode(_ value: String) -> Data? {
+            var base64 = value
+                .replacingOccurrences(of: "-", with: "+")
+                .replacingOccurrences(of: "_", with: "/")
+
+            let length = Double(base64.lengthOfBytes(using: String.Encoding.utf8))
+            let requiredLength = 4 * ceil(length / 4.0)
+            let paddingLength = requiredLength - length
+            if paddingLength > 0 {
+                let padding = "".padding(toLength: Int(paddingLength), withPad: "=", startingAt: 0)
+                base64 = base64 + padding
+            }
+            return Data(base64Encoded: base64, options: .ignoreUnknownCharacters)
+        }
+
+        func decodeJWTPart(_ value: String) -> [String: Any]? {
+            guard let bodyData = base64UrlDecode(value),
+                  let json = try? JSONSerialization.jsonObject(with: bodyData, options: []), let payload = json as? [String: Any] else {
+                return nil
+            }
+            return payload
+        }
+
+        let segments = jwt.components(separatedBy: ".")
+        return decodeJWTPart(segments[1]) ?? [:]
+    }
 }