implement Twitter OAuth.

app/src/main/java/chat/rocket/android/api/MethodCallHelper.java

@@ -171,9 +171,9 @@ public class MethodCallHelper {
   }
 
   /**
-   * Login with GitHub OAuth.
+   * Login with OAuth.
    */
-  public Task<Void> loginWithGitHub(final String credentialToken,
+  public Task<Void> loginWithOAuth(final String credentialToken,
       final String credentialSecret) {
     return call("login", TIMEOUT_MS, () -> new JSONArray().put(new JSONObject()
         .put("oauth", new JSONObject()

app/src/main/java/chat/rocket/android/fragment/oauth/GitHubOAuthFragment.java

@@ -152,7 +152,7 @@ public class GitHubOAuthFragment extends AbstractWebViewFragment {
 
   private void handleOAuthCallback(final String credentialToken, final String credentialSecret) {
     new MethodCallHelper(getContext(), serverConfigId)
-        .loginWithGitHub(credentialToken, credentialSecret)
+        .loginWithOAuth(credentialToken, credentialSecret)
         .continueWith(new LogcatIfError());
   }
 

app/src/main/java/chat/rocket/android/fragment/oauth/TwitterOAuthFragment.java

+package chat.rocket.android.fragment.oauth;
+
+import android.os.Bundle;
+import android.support.annotation.Nullable;
+import android.text.TextUtils;
+import android.util.Base64;
+import android.webkit.JavascriptInterface;
+import android.webkit.WebView;
+import chat.rocket.android.api.MethodCallHelper;
+import chat.rocket.android.fragment.AbstractWebViewFragment;
+import chat.rocket.android.helper.LogcatIfError;
+import chat.rocket.android.model.ServerConfig;
+import chat.rocket.android.model.ddp.MeteorLoginServiceConfiguration;
+import chat.rocket.android.realm_helper.RealmStore;
+import hugo.weaving.DebugLog;
+import java.nio.charset.Charset;
+import org.json.JSONException;
+import org.json.JSONObject;
+import timber.log.Timber;
+
+public class TwitterOAuthFragment extends AbstractWebViewFragment {
+
+  private String serverConfigId;
+  private String hostname;
+  private String url;
+  private boolean resultOK;
+
+  /**
+   * create new Fragment with ServerConfig-ID.
+   */
+  public static TwitterOAuthFragment create(final String serverConfigId) {
+    Bundle args = new Bundle();
+    args.putString("serverConfigId", serverConfigId);
+    TwitterOAuthFragment fragment = new TwitterOAuthFragment();
+    fragment.setArguments(args);
+    return fragment;
+  }
+
+  private boolean hasValidArgs(Bundle args) {
+    return args != null
+        && args.containsKey("serverConfigId");
+  }
+
+  @Override public void onCreate(@Nullable Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+    Bundle args = getArguments();
+    if (!hasValidArgs(args)) {
+      throw new IllegalArgumentException(
+          "serverConfigId required");
+    }
+
+    serverConfigId = args.getString("serverConfigId");
+    ServerConfig serverConfig = RealmStore.getDefault().executeTransactionForRead(realm ->
+        realm.where(ServerConfig.class).equalTo("serverConfigId", serverConfigId).findFirst());
+    MeteorLoginServiceConfiguration oauthConfig =
+        RealmStore.get(serverConfigId).executeTransactionForRead(realm ->
+            realm.where(MeteorLoginServiceConfiguration.class)
+                .equalTo("service", "twitter")
+                .findFirst());
+    if (serverConfig == null || oauthConfig == null) {
+      throw new IllegalArgumentException(
+          "Invalid serverConfigId given,");
+    }
+    hostname = serverConfig.getHostname();
+    url = generateURL();
+  }
+
+  private String generateURL() {
+    try {
+      String state = Base64.encodeToString(new JSONObject().put("loginStyle", "popup")
+          .put("credentialToken", "twitter" + System.currentTimeMillis())
+          .put("isCordova", true)
+          .toString()
+          .getBytes(Charset.forName("UTF-8")), Base64.NO_WRAP);
+
+      return "https://" + hostname + "/_oauth/twitter/?requestTokenAndRedirect=true&state=" + state;
+    } catch (Exception exception) {
+      Timber.e(exception, "failed to generate Twitter OAUth URL");
+    }
+    return null;
+  }
+
+  @Override protected void navigateToInitialPage(WebView webview) {
+    if (TextUtils.isEmpty(url)) {
+      finish();
+      return;
+    }
+
+    resultOK = false;
+    webview.loadUrl(url);
+    webview.addJavascriptInterface(new JSInterface(result -> {
+      // onPageFinish is called twice... Should ignore latter one.
+      if (resultOK) {
+        return;
+      }
+
+      if (result != null && result.optBoolean("setCredentialToken", false)) {
+        try {
+          final String credentialToken = result.getString("credentialToken");
+          final String credentialSecret = result.getString("credentialSecret");
+
+          handleOAuthCallback(credentialToken, credentialSecret);
+          resultOK = true;
+        } catch (JSONException exception) {
+          Timber.e(exception, "failed to parse OAuth result.");
+        }
+      }
+
+      onOAuthCompleted();
+    }), "_rocketchet_hook");
+  }
+
+  @DebugLog
+  @Override protected void onPageLoaded(WebView webview, String url) {
+    super.onPageLoaded(webview, url);
+
+
+    if (url.contains(hostname) && url.contains("_oauth/twitter?close")) {
+      final String jsHookUrl = "javascript:"
+          + "window._rocketchet_hook.handleConfig(document.getElementById('config').innerText);";
+      webview.loadUrl(jsHookUrl);
+    }
+  }
+
+  private interface JSInterfaceCallback {
+    void hanldeResult(@Nullable JSONObject result);
+  }
+
+  private static final class JSInterface {
+    private final JSInterfaceCallback jsInterfaceCallback;
+
+    JSInterface(JSInterfaceCallback callback) {
+      jsInterfaceCallback = callback;
+    }
+
+    @JavascriptInterface public void handleConfig(String config) {
+      try {
+        jsInterfaceCallback.hanldeResult(new JSONObject(config));
+      } catch (Exception exception) {
+        jsInterfaceCallback.hanldeResult(null);
+      }
+    }
+  }
+
+  private void handleOAuthCallback(final String credentialToken, final String credentialSecret) {
+    new MethodCallHelper(getContext(), serverConfigId)
+        .loginWithOAuth(credentialToken, credentialSecret)
+        .continueWith(new LogcatIfError());
+  }
+
+  private void onOAuthCompleted() {
+
+  }
+}

app/src/main/java/chat/rocket/android/fragment/server_config/LoginFragment.java

@@ -8,6 +8,7 @@ import android.widget.TextView;
 import chat.rocket.android.R;
 import chat.rocket.android.fragment.oauth.GitHubOAuthFragment;
 import chat.rocket.android.api.MethodCallHelper;
+import chat.rocket.android.fragment.oauth.TwitterOAuthFragment;
 import chat.rocket.android.helper.TextUtils;
 import chat.rocket.android.model.ddp.MeteorLoginServiceConfiguration;
 import chat.rocket.android.realm_helper.RealmListObserver;
@@ -77,7 +78,7 @@ public class LoginFragment extends AbstractServerConfigFragment {
           && "twitter".equals(authProvider.getService())) {
         hasTwitter = true;
         btnTwitter.setOnClickListener(view -> {
-
+          showFragmentWithBackStack(TwitterOAuthFragment.create(serverConfigId));
         });
       }
       if (!hasGitHub

app/src/main/res/layout/fragment_login.xml

@@ -24,7 +24,6 @@
                 android:layout_width="48dp"
                 android:layout_height="48dp"
                 android:layout_marginEnd="@dimen/margin_8"
-                android:enabled="false"
                 android:text="@string/fa_twitter"
                 android:textSize="16dp" />