Add explicit FieldValue canonicalization (#1178)

Author: schmidt-sebastian

firebase-firestore/src/main/java/com/google/firebase/firestore/model/value/ProtoValues.java

@@ -24,6 +24,8 @@
 import com.google.firestore.v1.Value;
 import com.google.protobuf.Timestamp;
 import com.google.type.LatLng;
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
@@ -249,4 +251,93 @@ private static int compareMaps(MapValue left, MapValue right) {
     // Only equal if both iterators are exhausted.
     return Util.compareBooleans(iterator1.hasNext(), iterator2.hasNext());
   }
+
+  /** Generate the canonical ID for the provided field value (as used in Target serialization). */
+  public static String canonicalId(Value value) {
+    StringBuilder builder = new StringBuilder();
+    canonifyValue(builder, value);
+    return builder.toString();
+  }
+
+  // TODO(mrschmidt): Use in target serialization and migrate all existing TargetData
+  private static void canonifyValue(StringBuilder builder, Value value) {
+    switch (value.getValueTypeCase()) {
+      case NULL_VALUE:
+        builder.append("null");
+        break;
+      case BOOLEAN_VALUE:
+        builder.append(value.getBooleanValue());
+        break;
+      case INTEGER_VALUE:
+        builder.append(value.getIntegerValue());
+        break;
+      case DOUBLE_VALUE:
+        builder.append(value.getDoubleValue());
+        break;
+      case TIMESTAMP_VALUE:
+        canonifyTimestamp(builder, value.getTimestampValue());
+        break;
+      case STRING_VALUE:
+        builder.append(value.getStringValue());
+        break;
+      case BYTES_VALUE:
+        builder.append(Util.toDebugString(value.getBytesValue()));
+        break;
+      case REFERENCE_VALUE:
+        // TODO(mrschmidt): Use document key only
+        builder.append(value.getReferenceValue());
+        break;
+      case GEO_POINT_VALUE:
+        canonifyGeoPoint(builder, value.getGeoPointValue());
+        break;
+      case ARRAY_VALUE:
+        canonifyArray(builder, value.getArrayValue());
+        break;
+      case MAP_VALUE:
+        canonifyObject(builder, value.getMapValue());
+        break;
+      default:
+        throw fail("Invalid value type: " + value.getValueTypeCase());
+    }
+  }
+
+  private static void canonifyTimestamp(StringBuilder builder, Timestamp timestamp) {
+    builder.append(String.format("time(%s,%s)", timestamp.getSeconds(), timestamp.getNanos()));
+  }
+
+  private static void canonifyGeoPoint(StringBuilder builder, LatLng latLng) {
+    builder.append(String.format("geo(%s,%s)", latLng.getLatitude(), latLng.getLongitude()));
+  }
+
+  private static void canonifyObject(StringBuilder builder, MapValue mapValue) {
+    // Even though MapValue are likely sorted correctly based on their insertion order (e.g. when
+    // received from the backend), local modifications can bring elements out of order. We need to
+    // re-sort the elements to ensure that canonical IDs are independent of insertion order.
+    List<String> keys = new ArrayList<>(mapValue.getFieldsMap().keySet());
+    Collections.sort(keys);
+
+    builder.append("{");
+    boolean first = true;
+    for (String key : keys) {
+      if (!first) {
+        builder.append(",");
+      } else {
+        first = false;
+      }
+      builder.append(key).append(":");
+      canonifyValue(builder, mapValue.getFieldsOrThrow(key));
+    }
+    builder.append("}");
+  }
+
+  private static void canonifyArray(StringBuilder builder, ArrayValue arrayValue) {
+    builder.append("[");
+    for (int i = 0; i < arrayValue.getValuesCount(); ++i) {
+      canonifyValue(builder, arrayValue.getValues(i));
+      if (i != arrayValue.getValuesCount() - 1) {
+        builder.append(",");
+      }
+    }
+    builder.append("]");
+  }
 }

firebase-firestore/src/test/java/com/google/firebase/firestore/model/FieldValueTest.java

@@ -35,6 +35,7 @@
 import com.google.firebase.firestore.model.protovalue.ObjectValue;
 import com.google.firebase.firestore.model.protovalue.PrimitiveValue;
 import com.google.firebase.firestore.model.value.FieldValue;
+import com.google.firebase.firestore.model.value.ProtoValues;
 import com.google.firebase.firestore.model.value.ServerTimestampValue;
 import com.google.firebase.firestore.testutil.ComparatorTester;
 import com.google.firestore.v1.Value;
@@ -366,6 +367,36 @@ public void testValueOrdering() {
         .testCompare();
   }
 
+  @Test
+  public void testCanonicalIds() {
+    assertCanonicalId(wrap(null), "null");
+    assertCanonicalId(wrap(true), "true");
+    assertCanonicalId(wrap(false), "false");
+    assertCanonicalId(wrap(1), "1");
+    assertCanonicalId(wrap(1.0), "1.0");
+    assertCanonicalId(wrap(new Timestamp(30, 60)), "time(30,60)");
+    assertCanonicalId(wrap("a"), "a");
+    assertCanonicalId(wrap(blob(1, 2, 3)), "010203");
+    assertCanonicalId(
+        wrapRef(dbId("p1", "d1"), key("c1/doc1")), "projects/p1/databases/d1/documents/c1/doc1");
+    assertCanonicalId(wrap(new GeoPoint(30, 60)), "geo(30.0,60.0)");
+    assertCanonicalId(wrap(Arrays.asList(1, 2, 3)), "[1,2,3]");
+    assertCanonicalId(wrap(map("a", 1, "b", 2, "c", "3")), "{a:1,b:2,c:3}");
+    assertCanonicalId(
+        wrap(map("a", Arrays.asList("b", map("c", new GeoPoint(30, 60))))),
+        "{a:[b,{c:geo(30.0,60.0)}]}");
+  }
+
+  @Test
+  public void testObjectCanonicalIdsIgnoreSortOrder() {
+    assertCanonicalId(wrap(map("a", 1, "b", 2, "c", "3")), "{a:1,b:2,c:3}");
+    assertCanonicalId(wrap(map("c", 3, "b", 2, "a", "1")), "{a:1,b:2,c:3}");
+  }
+
+  private void assertCanonicalId(PrimitiveValue fieldValue, String expectedCanonicalId) {
+    assertEquals(expectedCanonicalId, ProtoValues.canonicalId(fieldValue.toProto()));
+  }
+
   private ObjectValue setField(ObjectValue objectValue, String fieldPath, PrimitiveValue value) {
     return objectValue.toBuilder().set(field(fieldPath), value.toProto()).build();
   }