Reverse ReferenceWithHistory.dump() order

This commit switches the ordering of ReferenceWithHistory.dump() so the oldest
entries are output first followed by newer ones, i.e. traditional log ordering.

Tests are updated to confirm ReferenceWithHistory dump output.

Bug: 204855374
Test: atest services/tests/servicestests/src/com/android/server/timedetector/ReferenceWithHistoryTest.java
Test: adb shell dumpsys time_zone_detector
Change-Id: Ia098492fc6056fdbb8ef9d8ca1128bf0f51d113b

services/core/java/com/android/server/timezonedetector/ReferenceWithHistory.java

@@ -25,6 +25,7 @@ import android.util.IndentingPrintWriter;
 
 import java.time.Duration;
 import java.util.ArrayDeque;
+import java.util.Iterator;
 
 /**
  * A class that behaves like the following definition, except it stores the history of values set
@@ -112,9 +113,11 @@ public final class ReferenceWithHistory<V> {
         if (mValues == null) {
             ipw.println("{Empty}");
         } else {
-            int i = mSetCount;
-            for (TimestampedValue<V> valueHolder : mValues) {
-                ipw.print(--i);
+            int i = mSetCount - mValues.size();
+            Iterator<TimestampedValue<V>> reverseIterator = mValues.descendingIterator();
+            while (reverseIterator.hasNext()) {
+                TimestampedValue<V> valueHolder = reverseIterator.next();
+                ipw.print(i++);
                 ipw.print("@");
                 ipw.print(Duration.ofMillis(valueHolder.getReferenceTimeMillis()).toString());
                 ipw.print(": ");

services/tests/servicestests/src/com/android/server/timedetector/ReferenceWithHistoryTest.java

@@ -17,17 +17,19 @@
 package com.android.server.timedetector;
 
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+import android.util.IndentingPrintWriter;
 
 import androidx.test.runner.AndroidJUnit4;
 
-import com.android.internal.util.IndentingPrintWriter;
 import com.android.server.timezonedetector.ReferenceWithHistory;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
 import java.io.StringWriter;
+import java.util.Arrays;
 
 @RunWith(AndroidJUnit4.class)
 public class ReferenceWithHistoryTest {
@@ -41,31 +43,34 @@ public class ReferenceWithHistoryTest {
 
         // Check unset behavior.
         compareGet(referenceWithHistory, reference, null);
-        assertNotNull(dumpReferenceWithHistory(referenceWithHistory));
+        assertDumpContent(referenceWithHistory);
         compareToString(referenceWithHistory, reference, "null");
 
         // Try setting null.
         setAndCompareReturnValue(referenceWithHistory, reference, null);
         compareGet(referenceWithHistory, reference, null);
-        assertNotNull(dumpReferenceWithHistory(referenceWithHistory));
+        assertDumpContent(referenceWithHistory, new DumpLine(0, "null"));
         compareToString(referenceWithHistory, reference, "null");
 
         // Try setting a non-null value.
         setAndCompareReturnValue(referenceWithHistory, reference, "Foo");
         compareGet(referenceWithHistory, reference, "Foo");
-        assertNotNull(dumpReferenceWithHistory(referenceWithHistory));
+        assertDumpContent(referenceWithHistory,
+                new DumpLine(0, "null"), new DumpLine(1, "Foo"));
         compareToString(referenceWithHistory, reference, "Foo");
 
         // Try setting null again.
-        setAndCompareReturnValue(referenceWithHistory, reference, "Foo");
-        compareGet(referenceWithHistory, reference, "Foo");
-        assertNotNull(dumpReferenceWithHistory(referenceWithHistory));
-        compareToString(referenceWithHistory, reference, "Foo");
+        setAndCompareReturnValue(referenceWithHistory, reference, null);
+        compareGet(referenceWithHistory, reference, null);
+        assertDumpContent(referenceWithHistory,
+                new DumpLine(1, "Foo"), new DumpLine(2, "null"));
+        compareToString(referenceWithHistory, reference, "null");
 
         // Try a non-null value again.
         setAndCompareReturnValue(referenceWithHistory, reference, "Bar");
         compareGet(referenceWithHistory, reference, "Bar");
-        assertNotNull(dumpReferenceWithHistory(referenceWithHistory));
+        assertDumpContent(referenceWithHistory,
+                new DumpLine(2, "null"), new DumpLine(3, "Bar"));
         compareToString(referenceWithHistory, reference, "Bar");
     }
 
@@ -132,11 +137,54 @@ public class ReferenceWithHistoryTest {
         assertEquals(expected, referenceWithHistory.toString());
     }
 
-    private static String dumpReferenceWithHistory(ReferenceWithHistory<?> referenceWithHistory) {
+    private static void assertDumpContent(
+            ReferenceWithHistory<?> referenceWithHistory, DumpLine... expectedLines) {
+        String[] actualLines = dumpReferenceWithHistory(referenceWithHistory);
+
+        if (expectedLines.length == 0) {
+            String expectedEmptyOutput = "{Empty}";
+            assertEquals(expectedEmptyOutput, 1, actualLines.length);
+            assertEquals(expectedEmptyOutput, actualLines[0]);
+        } else {
+            assertEquals("Expected=" + Arrays.toString(expectedLines)
+                            + ", actual=" + Arrays.toString(actualLines),
+                    expectedLines.length, actualLines.length);
+            for (int i = 0; i < expectedLines.length; i++) {
+                DumpLine expectedLine = expectedLines[i];
+                String actualLine = actualLines[i];
+                assertTrue("i=" + i + ", expected=" + expectedLine + ", actual=" + actualLine,
+                        actualLine.startsWith(Integer.toString(expectedLine.mIndex)));
+                assertTrue("i=" + i + ", expected=" + expectedLine + ", actual=" + actualLine,
+                        actualLine.endsWith(expectedLine.mLine));
+            }
+        }
+    }
+
+    private static String[] dumpReferenceWithHistory(ReferenceWithHistory<?> referenceWithHistory) {
         StringWriter stringWriter = new StringWriter();
         try (IndentingPrintWriter ipw = new IndentingPrintWriter(stringWriter, " ")) {
             referenceWithHistory.dump(ipw);
-            return stringWriter.toString();
+            return stringWriter.toString().split("\n");
+        }
+    }
+
+    /** An expected line of {@link ReferenceWithHistory#dump} output. */
+    private static class DumpLine {
+
+        final int mIndex;
+        final String mLine;
+
+        DumpLine(int index, String line) {
+            mIndex = index;
+            mLine = line;
+        }
+
+        @Override
+        public String toString() {
+            return "DumpLine{"
+                    + "mIndex=" + mIndex
+                    + ", mLine='" + mLine + '\''
+                    + '}';
         }
     }
 }