Add REST call to get orphan links

bundles/org.openhab.core.io.rest.core/src/main/java/org/openhab/core/io/rest/core/internal/link/ItemChannelLinkResource.java

@@ -38,6 +38,7 @@
 import org.openhab.core.io.rest.RESTConstants;
 import org.openhab.core.io.rest.RESTResource;
 import org.openhab.core.io.rest.Stream2JSONInputStream;
+import org.openhab.core.io.rest.core.link.BrokenItemChannelLinkDTO;
 import org.openhab.core.io.rest.core.link.EnrichedItemChannelLinkDTO;
 import org.openhab.core.io.rest.core.link.EnrichedItemChannelLinkDTOMapper;
 import org.openhab.core.items.Item;
@@ -52,6 +53,7 @@
 import org.openhab.core.thing.link.AbstractLink;
 import org.openhab.core.thing.link.ItemChannelLink;
 import org.openhab.core.thing.link.ItemChannelLinkRegistry;
+import org.openhab.core.thing.link.ItemChannelLinkRegistry.ItemChannelLinkProblem;
 import org.openhab.core.thing.link.ManagedItemChannelLinkProvider;
 import org.openhab.core.thing.link.dto.ItemChannelLinkDTO;
 import org.openhab.core.thing.profiles.ProfileType;
@@ -87,6 +89,7 @@
  * @author Yannick Schaus - Added filters to getAll
  * @author Markus Rathgeb - Migrated to JAX-RS Whiteboard Specification
  * @author Wouter Born - Migrated to OpenAPI annotations
+ * @author Arne Seime - Added orphan links detection
  */
 @Component(service = { RESTResource.class, ItemChannelLinkResource.class })
 @JaxrsResource
@@ -314,4 +317,18 @@ private boolean isEditable(String linkId) {
         }
         return thing.getChannel(channelUID);
     }
+
+    @GET
+    @Path("/orphans")
+    @Operation(operationId = "getOrphanLinks", summary = "Get orphan links between items and broken/non-existent thing channels", responses = {
+            @ApiResponse(responseCode = "200", description = "List of broken links") })
+    public Response getOrphanLinks() {
+        Map<ItemChannelLink, ItemChannelLinkProblem> orphanLinks = itemChannelLinkRegistry.getOrphanLinks();
+        List<BrokenItemChannelLinkDTO> brokenLinks = orphanLinks.entrySet().stream()
+                .map(e -> new BrokenItemChannelLinkDTO(EnrichedItemChannelLinkDTOMapper.map(e.getKey(),
+                        managedItemChannelLinkProvider.get(e.getKey().getUID()) != null), e.getValue()))
+                .toList();
+
+        return Response.ok(brokenLinks).build();
+    }
 }

bundles/org.openhab.core.io.rest.core/src/main/java/org/openhab/core/io/rest/core/link/BrokenItemChannelLinkDTO.java

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) 2010-2024 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.core.io.rest.core.link;
+
+import org.openhab.core.thing.link.ItemChannelLinkRegistry.ItemChannelLinkProblem;
+
+/**
+ * Transfer object for broken item channel links.
+ *
+ * @author Arne Seime - Initial contribution
+ */
+public class BrokenItemChannelLinkDTO {
+    public EnrichedItemChannelLinkDTO itemChannelLink;
+
+    public ItemChannelLinkProblem problem;
+
+    public BrokenItemChannelLinkDTO(EnrichedItemChannelLinkDTO itemChannelLink, ItemChannelLinkProblem problem) {
+        this.itemChannelLink = itemChannelLink;
+        this.problem = problem;
+    }
+}

bundles/org.openhab.core.thing/src/main/java/org/openhab/core/thing/link/ItemChannelLinkRegistry.java

@@ -12,9 +12,7 @@
  */
 package org.openhab.core.thing.link;
 
-import java.util.List;
-import java.util.Objects;
-import java.util.Set;
+import java.util.*;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -155,27 +153,54 @@ public int removeLinksForItem(final String itemName) {
     }
 
     /**
-     * Remove all orphaned (item or channel missing) links
+     * Remove all orphaned (item or channel missing) links that are editable
      *
+     * @see #getOrphanLinks()
      * @return the number of removed links
      */
     public int purge() {
         ManagedProvider<ItemChannelLink, String> managedProvider = getManagedProvider()
                 .orElseThrow(() -> new IllegalStateException("ManagedProvider is not available"));
 
-        Set<String> allItems = itemRegistry.stream().map(Item::getName).collect(Collectors.toSet());
-        Set<ChannelUID> allChannels = thingRegistry.stream().map(Thing::getChannels).flatMap(List::stream)
-                .map(Channel::getUID).collect(Collectors.toSet());
-
-        Set<String> toRemove = managedProvider.getAll().stream()
-                .filter(link -> !allItems.contains(link.getItemName()) || !allChannels.contains(link.getLinkedUID()))
-                .map(ItemChannelLink::getUID).collect(Collectors.toSet());
+        List<String> toRemove = getOrphanLinks().keySet().stream().map(ItemChannelLink::getUID)
+                .filter(i -> managedProvider.get(i) != null).toList();
 
         toRemove.forEach(managedProvider::remove);
 
         return toRemove.size();
     }
 
+    /**
+     * Get all orphan links (item or channel missing)
+     *
+     * @see #purge()
+     *
+     * @return a map with orphan links as key and reason they are broken as value
+     */
+    public Map<ItemChannelLink, ItemChannelLinkProblem> getOrphanLinks() {
+        Collection<Item> items = itemRegistry.getItems();
+        Collection<Thing> things = thingRegistry.getAll();
+
+        Map<ItemChannelLink, ItemChannelLinkProblem> results = new HashMap<>();
+
+        Collection<ChannelUID> channelUIDS = things.stream().map(Thing::getChannels).flatMap(List::stream)
+                .map(Channel::getUID).collect(Collectors.toSet());
+        Collection<String> itemNames = items.stream().map(Item::getName).collect(Collectors.toSet());
+
+        getAll().forEach(itemChannelLink -> {
+            if (!channelUIDS.contains(itemChannelLink.getLinkedUID())) {
+                if (!itemNames.contains(itemChannelLink.getItemName())) {
+                    results.put(itemChannelLink, ItemChannelLinkProblem.ITEM_AND_THING_CHANNEL_MISSING);
+                } else {
+                    results.put(itemChannelLink, ItemChannelLinkProblem.THING_CHANNEL_MISSING);
+                }
+            } else if (!itemNames.contains(itemChannelLink.getItemName())) {
+                results.put(itemChannelLink, ItemChannelLinkProblem.ITEM_MISSING);
+            }
+        });
+        return results;
+    }
+
     @Override
     protected void notifyListenersAboutAddedElement(final ItemChannelLink element) {
         super.notifyListenersAboutAddedElement(element);
@@ -193,4 +218,17 @@ protected void notifyListenersAboutUpdatedElement(final ItemChannelLink oldEleme
         super.notifyListenersAboutUpdatedElement(oldElement, element);
         // it is not needed to send an event, because links can not be updated
     }
+
+    private boolean isEditable(String linkId) {
+        if (getManagedProvider().isPresent()) {
+            return getManagedProvider().get().get(linkId) != null;
+        }
+        return false;
+    }
+
+    public enum ItemChannelLinkProblem {
+        THING_CHANNEL_MISSING,
+        ITEM_MISSING,
+        ITEM_AND_THING_CHANNEL_MISSING;
+    }
 }