feat: expose metadata endpoint (#2)

pom.xml

@@ -34,7 +34,7 @@
     </dependency>
     <dependency>
       <groupId>io.quarkus</groupId>
-      <artifactId>quarkus-resteasy-reactive</artifactId>
+      <artifactId>quarkus-resteasy-reactive-jackson</artifactId>
     </dependency>
     <dependency>
       <groupId>io.quarkus</groupId>

src/main/java/io/github/metacosm/power/PowerMeasurer.java

@@ -37,4 +37,8 @@ public Multi<double[]> startTracking(String pid) throws Exception {
         return periodicSensorCheck.map(registeredPIDMap -> registeredPIDMap.get(registeredPID))
                 .onCancellation().invoke(() -> sensor.unregister(registeredPID));
     }
+
+    public SensorMetadata metadata() {
+        return sensor.metadata();
+    }
 }

src/main/java/io/github/metacosm/power/PowerResource.java

@@ -15,11 +15,17 @@ public class PowerResource {
     @GET
     @Produces(MediaType.TEXT_PLAIN)
     @Path("{pid}")
-    public Multi<String> hello(@PathParam("pid") String pid) throws Exception {
+    public Multi<String> powerFor(@PathParam("pid") String pid) throws Exception {
         try {
             return measurer.startTracking(pid).map(Arrays::toString);
         } catch (IllegalArgumentException e) {
             throw new NotFoundException("Unknown process: " + pid);
         }
     }
+
+    @GET
+    @Path("metadata")
+    public SensorMetadata metadata() {
+        return measurer.metadata();
+    }
 }

src/main/java/io/github/metacosm/power/SensorMetadata.java

@@ -1,9 +1,16 @@
 package io.github.metacosm.power;
 
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+import java.util.Map;
+
 public interface SensorMetadata {
     record ComponentMetadata(String name, int index, String description, boolean isAttributed, String unit){};
 
     ComponentMetadata metadataFor(String component);
 
     int componentCardinality();
+
+    @JsonProperty("metadata")
+    Map<String, ComponentMetadata> getComponents();
 }

src/main/java/io/github/metacosm/power/sensors/linux/rapl/IntelRAPLSensor.java

@@ -30,26 +30,31 @@ public IntelRAPLSensor() {
             throw new RuntimeException("Failed to get RAPL energy readings, probably due to lack of read access ");
 
         raplFiles = files.values().toArray(new RAPLFile[0]);
-        final var metadata = new HashMap<String, Integer>(files.size());
+        final var metadata = new HashMap<String, SensorMetadata.ComponentMetadata>(files.size());
         int fileNb = 0;
         for (String name : files.keySet()) {
-            metadata.put(name, fileNb++);
+            metadata.put(name, new SensorMetadata.ComponentMetadata(name, fileNb++, name, false, "µJ"));
         }
         this.metadata = new SensorMetadata() {
 
             @Override
             public ComponentMetadata metadataFor(String component) {
-                final var index = metadata.get(component);
-                if (index == null) {
+                final var componentMetadata = metadata.get(component);
+                if (componentMetadata == null) {
                     throw new IllegalArgumentException("Unknown component: " + component);
                 }
-                return new ComponentMetadata(component, index, component, false, "µJ");
+                return componentMetadata;
             }
 
             @Override
             public int componentCardinality() {
                 return metadata.size();
             }
+
+            @Override
+            public Map<String, ComponentMetadata> getComponents() {
+                return metadata;
+            }
         };
         lastMeasuredSensorValues = new double[raplFiles.length];
     }

src/main/java/io/github/metacosm/power/sensors/macos/powermetrics/MacOSPowermetricsSensor.java

@@ -40,6 +40,11 @@ public ComponentMetadata metadataFor(String component) {
         public int componentCardinality() {
             return 4;
         }
+
+        @Override
+        public Map<String, ComponentMetadata> getComponents() {
+            return Map.of(cpu.name(), cpu, gpu.name(), gpu, ane.name(), ane, cpuShare.name(), cpuShare);
+        }
     };
 
     @Override