server flow added

src/resources/login/src/java/org/wyona/yanel/impl/resources/login/OAuth2CallbackResource.java

@@ -43,21 +43,57 @@ public View getView(String viewId) throws Exception {
 
         view.setResponse(false); // this resource writes the response itself
 
-        String state = getEnvironment().getRequest().getParameter("state");
-        log.warn("TODO: Check state '" + state + "' ...");
-
         HttpServletResponse response = getEnvironment().getResponse();
-        if (true) {
-            log.error("Something went wrong!");
-            response.setStatus(500);
-        } else {
-            response.setHeader("Location", "TODO");
+
+        try {
+            String state = getEnvironment().getRequest().getParameter("state");
+            log.warn("TODO: Check state '" + state + "' ...");
+            if (true) {
+                throw new Exception("Checking 'state' parameter failed!");
+            }
+
+            String token_endpoint = getDiscoveryDocument();
+            String code = getEnvironment().getRequest().getParameter("code");
+            String id_token = getAccessAndIdToken(token_endpoint, code);
+            String uniqueUserId = getPayload(id_token);
+
+            // TODO: Check whether user with uniqueUserId exists or otherwise create account for this new user
+
+            response.setHeader("Location", "en/projects/index.html"); // TODO: Make configurable
             response.setStatus(307);
+        } catch(Exception e) {
+            log.error(e.getMessage());
+            response.setStatus(500);
         }
 
         return view;
     }
 
+    /**
+     * @return URL of token endpoint
+     */
+    private String getDiscoveryDocument() {
+        // TODO: Make URL configurable and depending on provider, e.g. Google OpenID is using https://accounts.google.com/.well-known/openid-configuration
+        return "https://www.googleapis.com/oauth2/v4/token"; // TODO: Get URL from discovery document
+    }
+
+    /**
+     * @return id_token (JSON Web Token, containing user identity information
+     */
+    private String getAccessAndIdToken(String token_endpoint, String code) {
+        // TODO: Get access and Id token by sending a POST request to token_endpoint, see https://developers.google.com/identity/protocols/OpenIDConnect#server-flow or https://developers.google.com/identity/protocols/OpenIDConnect#exchangecode
+        return "TODO";
+    }
+
+    /**
+     * Get user information
+     */
+    private String getPayload(String id_token) {
+        // TODO: Analyze JWT, e.g. get unique user Id and user email and ... see https://developers.google.com/identity/protocols/OpenIDConnect#obtainuserinfo
+        //return "michaelwechner@gmail.com"; // TODO: Return 'email'
+        return "10769150350006150715113082367"; // TODO: Return 'sub'
+    }
+
     /**
      * @see org.wyona.yanel.core.api.attributes.ViewableV2#getViewDescriptors()
      */