Integrate tailwind css and create new button library (#2098)

Introduce tailwind as new frontend styling library to replace bulma in the longer run. Also create the first new ui library `ui-buttons` which will be the new standard for buttons ins SCM-Manager. In this library we reconsidered which types of buttons should be used to create a clean and consistent ui.

Co-authored-by: Eduard Heimbuch <eduard.heimbuch@cloudogu.com>

scm-webapp/src/main/java/sonia/scm/PushStateDispatcherProvider.java

@@ -40,7 +40,7 @@ import javax.inject.Provider;
 public class PushStateDispatcherProvider implements Provider<PushStateDispatcher> {
 
   @VisibleForTesting
-  static final String PROPERTY_TARGET = "sonia.scm.ui.proxy";
+  public static final String PROPERTY_TARGET = "sonia.scm.ui.proxy";
 
   private Provider<TemplatingPushStateDispatcher> templatingPushStateDispatcherProvider;
 

scm-webapp/src/main/java/sonia/scm/web/tailwind/StylesServlet.java

@@ -0,0 +1,111 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020-present Cloudogu GmbH and Contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package sonia.scm.web.tailwind;
+
+import com.github.sdorra.webresources.CacheControl;
+import com.github.sdorra.webresources.WebResourceSender;
+import com.google.common.io.ByteStreams;
+import com.google.inject.Inject;
+import com.google.inject.Singleton;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import sonia.scm.filter.WebElement;
+import sonia.scm.plugin.PluginLoader;
+import sonia.scm.plugin.UberWebResourceLoader;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.HttpURLConnection;
+import java.net.MalformedURLException;
+import java.net.URL;
+
+import static sonia.scm.PushStateDispatcherProvider.PROPERTY_TARGET;
+
+@Singleton
+@WebElement(value = "/styles.bundle.css")
+public class StylesServlet extends HttpServlet {
+  private static final Logger LOG = LoggerFactory.getLogger(StylesServlet.class);
+  private final UberWebResourceLoader webResourceLoader;
+  private final String target = System.getProperty(PROPERTY_TARGET);
+
+  private final WebResourceSender sender = WebResourceSender.create()
+    .withGZIP()
+    .withGZIPMinLength(512)
+    .withBufferSize(16384)
+    .withCacheControl(CacheControl.create().noCache());
+
+  @Inject
+  public StylesServlet(PluginLoader pluginLoader) {
+    this.webResourceLoader = pluginLoader.getUberWebResourceLoader();
+  }
+
+  @Override
+  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+    try {
+      URL url = webResourceLoader.getResource("/assets/webapp.tailwind.css");
+      if (url != null) {
+        // TODO: Merge css
+        sender.resource(url).get(request, response);
+      } else {
+        getLocally(createProxyUrl("/assets/webapp.tailwind.css"), request, response);
+      }
+    } catch (IOException ex) {
+      LOG.error("Error on getting the tailwind stylesheet", ex);
+      response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
+    }
+  }
+
+  private void getLocally(URL url, HttpServletRequest request, HttpServletResponse response) throws IOException {
+    HttpURLConnection connection = openConnection(url);
+    connection.setRequestMethod(request.getMethod());
+
+    int responseCode = connection.getResponseCode();
+    response.setStatus(responseCode);
+    try (InputStream input = getConnectionInput(connection); OutputStream output = response.getOutputStream()) {
+      ByteStreams.copy(input, output);
+    }
+  }
+
+  private InputStream getConnectionInput(HttpURLConnection connection) throws IOException {
+    if (connection.getErrorStream() != null) {
+      return connection.getErrorStream();
+    }
+    return connection.getInputStream();
+  }
+
+  private URL createProxyUrl(String uri) throws MalformedURLException {
+    return new URL(target + uri);
+  }
+
+  private static HttpURLConnection openConnection(URL url) throws IOException {
+    return (HttpURLConnection) url.openConnection();
+  }
+
+}