[rest] Add endpoint for UoM information (#3611)

* [rest] Add endpoint for UoM information

Signed-off-by: Jan N. Klug <github@klug.nrw>

bundles/org.openhab.core.io.rest/src/main/java/org/openhab/core/io/rest/internal/resources/SystemInfoResource.java

@@ -23,9 +23,11 @@ import javax.ws.rs.core.UriInfo;
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
 import org.openhab.core.auth.Role;
+import org.openhab.core.i18n.UnitProvider;
 import org.openhab.core.io.rest.RESTConstants;
 import org.openhab.core.io.rest.RESTResource;
 import org.openhab.core.io.rest.internal.resources.beans.SystemInfoBean;
+import org.openhab.core.io.rest.internal.resources.beans.UoMInfoBean;
 import org.openhab.core.service.StartLevelService;
 import org.osgi.service.component.annotations.Activate;
 import org.osgi.service.component.annotations.Component;
@@ -64,10 +66,12 @@ public class SystemInfoResource implements RESTResource {
     public static final String PATH_SYSTEMINFO = "systeminfo";
 
     private final StartLevelService startLevelService;
+    private final UnitProvider unitProvider;
 
     @Activate
-    public SystemInfoResource(@Reference StartLevelService startLevelService) {
+    public SystemInfoResource(@Reference StartLevelService startLevelService, @Reference UnitProvider unitProvider) {
         this.startLevelService = startLevelService;
+        this.unitProvider = unitProvider;
     }
 
     @GET
@@ -79,4 +83,14 @@ public class SystemInfoResource implements RESTResource {
         final SystemInfoBean bean = new SystemInfoBean(startLevelService.getStartLevel());
         return Response.ok(bean).build();
     }
+
+    @GET
+    @Path("/uom")
+    @Produces(MediaType.APPLICATION_JSON)
+    @Operation(operationId = "getUoMInformation", summary = "Get all supported dimensions and their system units.", responses = {
+            @ApiResponse(responseCode = "200", description = "OK", content = @Content(schema = @Schema(implementation = UoMInfoBean.class))) })
+    public Response getUoMInfo(@Context UriInfo uriInfo) {
+        final UoMInfoBean bean = new UoMInfoBean(unitProvider);
+        return Response.ok(bean).build();
+    }
 }

bundles/org.openhab.core.io.rest/src/main/java/org/openhab/core/io/rest/internal/resources/beans/UoMInfoBean.java

@@ -0,0 +1,62 @@
+/**
+ * Copyright (c) 2010-2023 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.internal.resources.beans;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.Objects;
+
+import javax.measure.Quantity;
+import javax.measure.Unit;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.openhab.core.i18n.UnitProvider;
+import org.openhab.core.types.util.UnitUtils;
+
+/**
+ * This is a java bean that is used to define UoM information for the REST interface.
+ *
+ * @author Jan N. Klug - Initial contribution
+ */
+@NonNullByDefault
+public class UoMInfoBean {
+
+    public final UoMInfo uomInfo;
+
+    public static class UoMInfo {
+        public final List<DimensionInfo> dimensions;
+
+        public static class DimensionInfo {
+            public final String dimension;
+            public final String systemUnit;
+
+            public DimensionInfo(String dimension, String systemUnit) {
+                this.dimension = dimension;
+                this.systemUnit = systemUnit;
+            }
+        }
+
+        @SuppressWarnings({ "unchecked" })
+        public UoMInfo(UnitProvider unitProvider) {
+            dimensions = unitProvider.getAllDimensions().stream().map(dimension -> {
+                Unit<?> unit = unitProvider.getUnit((Class<? extends Quantity>) dimension);
+                String dimensionName = Objects.requireNonNull(UnitUtils.getDimensionName(unit));
+                return new DimensionInfo(dimensionName, unit.toString());
+            }).sorted(Comparator.comparing(a -> a.dimension)).toList();
+        }
+    }
+
+    public UoMInfoBean(UnitProvider unitProvider) {
+        uomInfo = new UoMInfo(unitProvider);
+    }
+}

bundles/org.openhab.core/src/main/java/org/openhab/core/i18n/UnitProvider.java

@@ -12,6 +12,8 @@
  */
 package org.openhab.core.i18n;
 
+import java.util.Collection;
+
 import javax.measure.Quantity;
 import javax.measure.Unit;
 import javax.measure.spi.SystemOfUnits;
@@ -44,4 +46,6 @@ public interface UnitProvider {
      * @return the {@link SystemOfUnits} which is currently set, must not be null.
      */
     SystemOfUnits getMeasurementSystem();
+
+    Collection<Class<? extends Quantity<?>>> getAllDimensions();
 }

bundles/org.openhab.core/src/main/java/org/openhab/core/internal/i18n/I18nProviderImpl.java

@@ -17,11 +17,13 @@ import static org.openhab.core.library.unit.MetricPrefix.HECTO;
 import java.text.MessageFormat;
 import java.time.DateTimeException;
 import java.time.ZoneId;
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.ResourceBundle;
+import java.util.Set;
 
 import javax.measure.Quantity;
 import javax.measure.Unit;
@@ -379,6 +381,11 @@ public class I18nProviderImpl
         return SIUnits.getInstance();
     }
 
+    @Override
+    public Collection<Class<? extends Quantity<?>>> getAllDimensions() {
+        return Set.copyOf(getDimensionMap().keySet());
+    }
+
     public static Map<Class<? extends Quantity<?>>, Map<SystemOfUnits, Unit<? extends Quantity<?>>>> getDimensionMap() {
         Map<Class<? extends Quantity<?>>, Map<SystemOfUnits, Unit<? extends Quantity<?>>>> dimensionMap = new HashMap<>();
 

bundles/org.openhab.core/src/test/java/org/openhab/core/internal/i18n/TestUnitProvider.java

@@ -12,7 +12,9 @@
  */
 package org.openhab.core.internal.i18n;
 
+import java.util.Collection;
 import java.util.Map;
+import java.util.Set;
 
 import javax.measure.Quantity;
 import javax.measure.Unit;
@@ -45,4 +47,9 @@ public class TestUnitProvider implements UnitProvider {
     public SystemOfUnits getMeasurementSystem() {
         return SIUnits.getInstance();
     }
+
+    @Override
+    public Collection<Class<? extends Quantity<?>>> getAllDimensions() {
+        return Set.of();
+    }
 }