Fix averageSince calculation (#2405)

* Fix averageSince calculation Signed-off-by: Jan N. Klug <jan.n.klug@rub.de>
eclipse-archived · Dec 17, 2016 · eae34a0 · eae34a0
1 parent 3ce6ba1
commit eae34a0
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Showing 2 changed files with 49 additions and 15 deletions.
diff --git a/...st/java/org/eclipse/smarthome/model/persistence/extensions/PersistenceExtensionsTest.java b/...st/java/org/eclipse/smarthome/model/persistence/extensions/PersistenceExtensionsTest.java
@@ -21,13 +21,15 @@
 import org.eclipse.smarthome.core.types.State;
 import org.eclipse.smarthome.model.persistence.tests.TestPersistenceService;
 import org.joda.time.DateMidnight;
+import org.joda.time.DateTime;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 
 /**
  * @author Kai Kreuzer - Initial contribution and API
  * @author Chris Jackson
+ * @author Jan N. Klug
  */
 @SuppressWarnings("deprecation")
 public class PersistenceExtensionsTest {
@@ -124,8 +126,13 @@ public void testMaximumSince() {
     @Test
     public void testAverageSince() {
         item.setState(new DecimalType(3025));
-        DecimalType average = PersistenceExtensions.averageSince(item, new DateMidnight(2003, 1, 1), "test");
-        assertEquals("2100", average.toString());
+        DateMidnight startStored = new DateMidnight(2003, 1, 1);
+        DateMidnight endStored = new DateMidnight(2012, 1, 1);
+        long storedInterval = endStored.getMillis() - startStored.getMillis();
+        long recentInterval = DateTime.now().getMillis() - endStored.getMillis();
+        double expected = (2007.4994 * storedInterval + 2518.5 * recentInterval) / (storedInterval + recentInterval);
+        DecimalType average = PersistenceExtensions.averageSince(item, startStored, "test");
+        assertEquals(expected, average.doubleValue(), 0.01);
     }
 
     @Test

diff --git a/...istence/src/org/eclipse/smarthome/model/persistence/extensions/PersistenceExtensions.java b/...istence/src/org/eclipse/smarthome/model/persistence/extensions/PersistenceExtensions.java
@@ -77,7 +77,8 @@ private static String getDefaultServiceId() {
                         .warn("There is no default persistence service configured!");
             }
         } else {
-            LoggerFactory.getLogger(PersistenceExtensions.class).warn("PersistenceServiceRegistryImpl is not available!");
+            LoggerFactory.getLogger(PersistenceExtensions.class)
+                    .warn("PersistenceServiceRegistryImpl is not available!");
         }
         return null;
     }
@@ -400,24 +401,50 @@ public static DecimalType averageSince(Item item, AbstractInstant timestamp, Str
         Iterable<HistoricItem> result = getAllStatesSince(item, timestamp, serviceId);
         Iterator<HistoricItem> it = result.iterator();
 
-        DecimalType value = (DecimalType) item.getStateAs(DecimalType.class);
-        if (value == null) {
-            value = DecimalType.ZERO;
-        }
+        BigDecimal total = BigDecimal.ZERO;
+
+        BigDecimal avgValue, timeSpan;
+        DecimalType lastState = null, thisState = null;
+        BigDecimal lastTimestamp = null, thisTimestamp = null;
+        BigDecimal firstTimestamp = null;
 
-        BigDecimal total = value.toBigDecimal();
-        int quantity = 1;
         while (it.hasNext()) {
-            State state = it.next().getState();
+            HistoricItem thisItem = it.next();
+            State state = thisItem.getState();
+
             if (state instanceof DecimalType) {
-                value = (DecimalType) state;
-                total = total.add(value.toBigDecimal());
-                quantity++;
+                thisState = (DecimalType) state;
+                thisTimestamp = BigDecimal.valueOf(thisItem.getTimestamp().getTime());
+                if (firstTimestamp == null) {
+                    firstTimestamp = thisTimestamp;
+                } else {
+                    avgValue = (thisState.toBigDecimal().add(lastState.toBigDecimal())).divide(BigDecimal.valueOf(2),
+                            MathContext.DECIMAL64);
+                    timeSpan = thisTimestamp.subtract(lastTimestamp);
+                    total = total.add(avgValue.multiply(timeSpan, MathContext.DECIMAL64));
+                }
+                lastTimestamp = thisTimestamp;
+                lastState = thisState;
             }
         }
-        BigDecimal average = total.divide(BigDecimal.valueOf(quantity), MathContext.DECIMAL64);
 
-        return new DecimalType(average);
+        if (lastState != null) {
+            thisState = (DecimalType) item.getStateAs(DecimalType.class);
+            thisTimestamp = BigDecimal.valueOf((new DateTime()).getMillis());
+            avgValue = (thisState.toBigDecimal().add(lastState.toBigDecimal())).divide(BigDecimal.valueOf(2),
+                    MathContext.DECIMAL64);
+            timeSpan = thisTimestamp.subtract(lastTimestamp);
+            total = total.add(avgValue.multiply(timeSpan, MathContext.DECIMAL64));
+        }
+
+        if (thisTimestamp != null) {
+            timeSpan = thisTimestamp.subtract(firstTimestamp, MathContext.DECIMAL64);
+
+            BigDecimal average = total.divide(timeSpan, MathContext.DECIMAL64);
+            return new DecimalType(average);
+        } else {
+            return null;
+        }
     }
 
     /**