diff --git a/src/components/scan.js b/src/components/scan.js
index 30feb17..5f4d005 100644
--- a/src/components/scan.js
+++ b/src/components/scan.js
@@ -1,6 +1,7 @@
 import React from "react";
 import PropTypes from 'prop-types';
-import {beep, CODE_TYPE, WORKER_TYPE} from "../helpers";
+import {beep, WORKER_TYPE} from "../helpers";
+import {CODE_TYPE} from "../transformers/base";
 import {Upnqr} from "../transformers/upnqr";
 import {Covid19} from "../transformers/covid19";
 import "../css/scan.css";
diff --git a/src/helpers.js b/src/helpers.js
index c2464d8..b87d43a 100644
--- a/src/helpers.js
+++ b/src/helpers.js
@@ -22,10 +22,4 @@ const WORKER_TYPE = {
   JS: "jsQr"
 };
 
-const CODE_TYPE = {
-  UPNQR: "UPNQR",
-  COVID19: "COVID",
-  RAW: "RAW"
-};
-
-export {beep, WORKER_TYPE, CODE_TYPE};
\ No newline at end of file
+export {beep, WORKER_TYPE};
\ No newline at end of file
diff --git a/src/transformers/base.js b/src/transformers/base.js
new file mode 100644
index 0000000..c6730f6
--- /dev/null
+++ b/src/transformers/base.js
@@ -0,0 +1,25 @@
+class Transformer {
+  codeType() {
+    return "TODO";
+  }
+
+  identified(raw) {
+    return false;
+  }
+
+  transform(raw) {
+    return "TODO";
+  }
+
+  static buttonCaption() {
+    return "TODO";
+  }
+}
+
+const CODE_TYPE = {
+  UPNQR: "UPNQR",
+  COVID19: "COVID",
+  RAW: "RAW"
+};
+
+export {Transformer, CODE_TYPE};
\ No newline at end of file
diff --git a/src/transformers/covid19.js b/src/transformers/covid19.js
index 7e625b3..f6099ef 100644
--- a/src/transformers/covid19.js
+++ b/src/transformers/covid19.js
@@ -1,11 +1,12 @@
-import {addCachedCerts, unpackAndVerify} from "@pathcheck/dcc-sdk";
-import {CODE_TYPE} from "../helpers";
 import {cachedCerts} from "./certs";
+import {CODE_TYPE, Transformer} from "./base";
+import {addCachedCerts, unpackAndVerify} from "@pathcheck/dcc-sdk";
 
-class Covid19 {
+class Covid19 extends Transformer {
   recognizer = "HC1:";
 
   constructor() {
+    super();
     addCachedCerts(cachedCerts);
   }
 
@@ -31,8 +32,8 @@ class Covid19 {
     const record = cwtPayload.get(-260).get(1);
 
     const dob = record.dob;
-    const name =  record.nam.fnt + "<<" + record.nam.gnt;
-    const national_name = record.nam.fn + " " + record.nam.gn;
+    const name =  record["nam"]["fnt"] + "<<" + record["nam"]["gnt"];
+    const national_name = record["nam"]["fn"] + " " + record["nam"]["gn"];
 
     const vaccination = this.extractVaccine(record);
     const test = this.extractTest(record);
@@ -42,25 +43,25 @@ class Covid19 {
 
   extractTest(record) {
     if (!record.t) return null;
-    const unique_cert_id = record.t[0].ci;
-    const issued_on = record.t[0].sc;
-    const issuer = record.t[0].is;
-    const test_type = record.t[0].tt;
-    const test_result = record.t[0].tr;
-    const country = record.t[0].co;
+    const unique_cert_id = record.t[0]["ci"];
+    const issued_on = record.t[0]["sc"];
+    const issuer = record.t[0]["is"];
+    const test_type = record.t[0]["tt"];
+    const test_result = record.t[0]["tr"];
+    const country = record.t[0]["co"];
 
     return {unique_cert_id, issued_on, issuer, test_type, test_result, country};
   };
 
   extractVaccine(record) {
-    if (!record.v) return null;
-    const unique_cert_id = record.v[0].ci;
-    const issued_on = record.v[0].dt;
-    const issuer = record.v[0].is;
-    const vaccine_type = record.v[0].mp;
-    const doses = record.v[0].dn;
-    const dose_series = record.v[0].sd;
-    const country = record.v[0].co;
+    if (!record["v"]) return null;
+    const unique_cert_id = record["v"][0]["ci"];
+    const issued_on = record["v"][0]["dt"];
+    const issuer = record["v"][0]["is"];
+    const vaccine_type = record["v"][0]["mp"];
+    const doses = record["v"][0]["dn"];
+    const dose_series = record["v"][0]["sd"];
+    const country = record["v"][0]["co"];
 
     return {unique_cert_id, issued_on, issuer, vaccine_type, doses, dose_series, country};
   };
@@ -84,7 +85,7 @@ class Covid19 {
     res += `Born: ${formatISO8601Date(json.dob)}\n`;
 
     if (json.vaccination) {
-      let vaccine_type = "";
+      let vaccine_type;
       switch (json.vaccination.vaccine_type) {
         case "EU/1/20/1528":
           vaccine_type = "Comirnaty (Pfizer)";
@@ -110,7 +111,7 @@ class Covid19 {
     }
 
     if (json.test) {
-      let test_type = "";
+      let test_type;
       switch (json.test.test_type) {
         case "LP217198-3":
           test_type = "Rapid immunoassay";
@@ -122,7 +123,7 @@ class Covid19 {
           test_type = json.test.test_type;
       }
 
-      let test_result = "";
+      let test_result;
       switch (json.test.test_result) {
         case "260415000":
           test_result = "Negative";
diff --git a/src/transformers/upnqr.js b/src/transformers/upnqr.js
index 152cc77..fb48a70 100644
--- a/src/transformers/upnqr.js
+++ b/src/transformers/upnqr.js
@@ -1,7 +1,7 @@
-import {CODE_TYPE} from "../helpers";
+import {CODE_TYPE, Transformer} from "./base";
 import {decode} from "upnqr";
 
-class Upnqr {
+class Upnqr extends Transformer {
   recognizer = "UPNQR";
 
   codeType() {