Added support for dashboard links to external services. (#185)

* Added dashboard support for links to external services.


Signed-off-by: Pauli Anttila <pauli.anttila@gmail.com>

bundles/org.openhab.ui.dashboard/README.md

@@ -0,0 +1,34 @@
+# Dashboard
+
+The openHAB dashboard is a landing page for the user where all openHAB UIs can be found.
+Dashboard support also links to external services.
+Links can be added to the dashboard by editing the `conf/services/dashboard.cfg` configuration file.
+
+## Link Configuration
+
+| Parameter name              | Type    | Description                                                                             |
+|-----------------------------|---------|-----------------------------------------------------------------------------------------|
+| <unique-name>.link-name     | String  | Name which is shown in the openHAB dashboard.                                           |
+| <unique-name>.link-url      | String  | URL to external service.                                                                |
+| <unique-name>.link-imageurl | String  | URL to image which is shown in the dashboard.                                           |
+
+Where `<unique-name>` is link unique identifier (see examples).
+
+## Image URL
+
+Browser fetch image from image URL. URL can be direct http link or data URIs according to [RFC2397](https://tools.ietf.org/html/rfc2397). If data URIs are used, browser should support them as well. All five major browsers (Chrome, Firefox, IE, Opera and Safari) support data URIs. See e.g. [https://www.base64-image.de](https://www.base64-image.de) to convert images to base64 coded data. 
+
+## Example configuration file
+
+```
+frontail.link-name=openHAB Log Viewer
+frontail.link-url=http://<server-adddress>:9001
+frontail.link-imageurl=../static/image.png
+
+nodered.link-name=Node-RED
+nodered.link-url=http://<server-adddress>:1880
+nodered.link-imageurl=data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAXwAAACfCAIAAA...QmCC
+
+```
+
+Note: **nodered** image data URL is not valid (it's shorten for the sake of clarity).

bundles/org.openhab.ui.dashboard/src/main/java/org/openhab/ui/dashboard/internal/DashboardService.java

@@ -11,6 +11,7 @@
 import java.io.IOException;
 import java.net.URL;
 import java.util.Hashtable;
+import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.CopyOnWriteArraySet;
 
@@ -40,7 +41,7 @@
  *
  * @author Kai Kreuzer - Initial contribution
  */
-@Component(service = DashboardService.class, immediate = true)
+@Component(service = DashboardService.class, immediate = true, name = "org.openhab.dashboard")
 public class DashboardService {
 
     public static final String DASHBOARD_ALIAS = "/start";
@@ -58,8 +59,12 @@ public class DashboardService {
 
     private BundleContext bundleContext;
 
+    private final static String LINK_NAME = "link-name";
+    private final static String LINK_URL = "link-url";
+    private final static String LINK_IMAGEURL = "link-imageurl";
+
     @Activate
-    protected void activate(ComponentContext componentContext) {
+    protected void activate(ComponentContext componentContext, Map<String, Object> properties) {
         try {
             bundleContext = componentContext.getBundleContext();
             Hashtable<String, String> props = new Hashtable<>();
@@ -78,6 +83,8 @@ protected void activate(ComponentContext componentContext) {
         } catch (NamespaceException | ServletException e) {
             logger.error("Error during dashboard startup: {}", e.getMessage());
         }
+
+        addTilesForExternalServices(properties);
     }
 
     @Deactivate
@@ -175,4 +182,24 @@ protected HttpServlet createServlet() {
         return new DashboardServlet(configurationAdmin, indexTemplate, entryTemplate, warnTemplate, setupTemplate,
                 tiles);
     }
+
+    private void addTilesForExternalServices(Map<String, Object> properties) {
+        for (String key : properties.keySet()) {
+            if (key.endsWith(LINK_NAME)) {
+                if (key.length() > LINK_NAME.length()) {
+                    // get prefix from link name
+                    String linkname = key.substring(0, key.length() - LINK_NAME.length());
+
+                    String name = (String) properties.get(linkname + LINK_NAME);
+                    String url = (String) properties.get(linkname + LINK_URL);
+                    String imageUrl = (String) properties.get(linkname + LINK_IMAGEURL);
+
+                    logger.debug("Add link: {}", name);
+
+                    addDashboardTile(new ExternalServiceTile.DashboardTileBuilder().withName(name).withUrl(url)
+                            .withImageUrl(imageUrl).build());
+                }
+            }
+        }
+    }
 }

bundles/org.openhab.ui.dashboard/src/main/java/org/openhab/ui/dashboard/internal/ExternalServiceTile.java

@@ -0,0 +1,82 @@
+/**
+ * Copyright (c) 2010-2017 by the respective copyright holders.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.openhab.ui.dashboard.internal;
+
+import org.openhab.ui.dashboard.DashboardTile;
+
+/**
+ * The dashboard tile for external services.
+ *
+ * @author Pauli Anttila - Initial contribution
+ */
+public class ExternalServiceTile implements DashboardTile {
+    private String name;
+    private String url;
+    private String overlay;
+    private String imageUrl;
+
+    private ExternalServiceTile(DashboardTileBuilder builder) {
+        this.name = builder.name;
+        this.url = builder.url;
+        this.overlay = builder.overlay;
+        this.imageUrl = builder.imageUrl;
+    }
+
+    @Override
+    public String getName() {
+        return name;
+    }
+
+    @Override
+    public String getUrl() {
+        return url;
+    }
+
+    @Override
+    public String getOverlay() {
+        return overlay;
+    }
+
+    @Override
+    public String getImageUrl() {
+        return imageUrl;
+    }
+
+    public static class DashboardTileBuilder {
+
+        private String name;
+        private String url;
+        private String overlay;
+        private String imageUrl;
+
+        public DashboardTileBuilder withName(String name) {
+            this.name = name;
+            return this;
+        }
+
+        public DashboardTileBuilder withUrl(String url) {
+            this.url = url;
+            return this;
+        }
+
+        public DashboardTileBuilder withOverlay(String overlay) {
+            this.overlay = overlay;
+            return this;
+        }
+
+        public DashboardTileBuilder withImageUrl(String imageUrl) {
+            this.imageUrl = imageUrl;
+            return this;
+        }
+
+        public ExternalServiceTile build() {
+            return new ExternalServiceTile(this);
+        }
+    }
+}