feat: add file-backed sensor

Author: metacosm

backend/src/main/java/net/laprun/sustainability/power/sensors/macos/powermetrics/FileMacOSPowermetricsSensor.java

@@ -0,0 +1,44 @@
+package net.laprun.sustainability.power.sensors.macos.powermetrics;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.InputStream;
+
+/**
+ * The aim of this sensor is to only perform one long measure and then read the power information from it once done,
+ */
+public class FileMacOSPowermetricsSensor extends MacOSPowermetricsSensor {
+    private final File file;
+    private boolean started;
+
+    public FileMacOSPowermetricsSensor(File file) {
+        this.file = file;
+    }
+
+    @Override
+    protected InputStream getInputStream() {
+        try {
+            return new FileInputStream(file);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    @Override
+    public boolean isStarted() {
+        return started;
+    }
+
+    @Override
+    public void start(long samplingFrequencyInMillis) {
+        if (!started) {
+            started = true;
+        }
+    }
+
+    @Override
+    public void stop() {
+        started = false;
+        initMetadata(getInputStream());
+    }
+}