Pipeline Expressions Refactor (#1946)

* Refactor

* Cleanup

Author: tom-andersen

google-cloud-firestore/src/main/java/com/google/cloud/firestore/UserDataConverter.java

@@ -41,6 +41,8 @@
 
 /** Converts user input into the Firestore Value representation. */
 class UserDataConverter {
+
+  static final Value NULL_VALUE = Value.newBuilder().setNullValue(NullValue.NULL_VALUE).build();
   private static final Logger LOGGER = Logger.getLogger(UserDataConverter.class.getName());
 
   /** Controls the behavior for field deletes. */
@@ -120,8 +122,9 @@ static Value encodeValue(
               + " as an argument at field '%s'.",
           path);
       return null;
+
     } else if (sanitizedObject == null) {
-      return Value.newBuilder().setNullValue(NullValue.NULL_VALUE).build();
+      return NULL_VALUE;
     } else if (sanitizedObject instanceof String) {
       return Value.newBuilder().setStringValue((String) sanitizedObject).build();
     } else if (sanitizedObject instanceof Integer) {

google-cloud-firestore/src/main/java/com/google/cloud/firestore/pipeline/expressions/Accumulator.java

@@ -17,12 +17,18 @@
 package com.google.cloud.firestore.pipeline.expressions;
 
 import com.google.api.core.BetaApi;
+import com.google.common.collect.ImmutableList;
 
 @BetaApi
-public interface Accumulator extends Expr {
+public abstract class Accumulator extends Function {
+
+  protected Accumulator(String name, ImmutableList<? extends Expr> params) {
+    super(name, params);
+  }
+
   @BetaApi
   @Override
-  default ExprWithAlias<Accumulator> as(String fieldName) {
+  public ExprWithAlias<Accumulator> as(String fieldName) {
     return new ExprWithAlias<>(this, fieldName);
   }
 }

google-cloud-firestore/src/main/java/com/google/cloud/firestore/pipeline/expressions/And.java

@@ -22,7 +22,7 @@
 import java.util.List;
 
 @BetaApi
-public final class And extends Function implements FilterCondition {
+public final class And extends FilterCondition {
   @InternalApi
   And(List<FilterCondition> conditions) {
     super("and", ImmutableList.copyOf(conditions));

google-cloud-firestore/src/main/java/com/google/cloud/firestore/pipeline/expressions/ArrayContains.java

@@ -21,7 +21,7 @@
 import com.google.common.collect.ImmutableList;
 
 @BetaApi
-public final class ArrayContains extends Function implements FilterCondition {
+public final class ArrayContains extends FilterCondition {
   @InternalApi
   ArrayContains(Expr array, Expr element) {
     super(

google-cloud-firestore/src/main/java/com/google/cloud/firestore/pipeline/expressions/ArrayContainsAll.java

@@ -22,7 +22,7 @@
 import java.util.List;
 
 @BetaApi
-public final class ArrayContainsAll extends Function implements FilterCondition {
+public final class ArrayContainsAll extends FilterCondition {
   @InternalApi
   ArrayContainsAll(Expr array, List<Expr> elements) {
     super("array_contains_all", ImmutableList.of(array, new ListOfExprs(elements)));

google-cloud-firestore/src/main/java/com/google/cloud/firestore/pipeline/expressions/ArrayContainsAny.java

@@ -22,7 +22,7 @@
 import java.util.List;
 
 @BetaApi
-public final class ArrayContainsAny extends Function implements FilterCondition {
+public final class ArrayContainsAny extends FilterCondition {
   @InternalApi
   ArrayContainsAny(Expr array, List<Expr> elements) {
     super("array_contains_any", ImmutableList.of(array, new ListOfExprs(elements)));

google-cloud-firestore/src/main/java/com/google/cloud/firestore/pipeline/expressions/Avg.java

@@ -21,7 +21,7 @@
 import com.google.common.collect.ImmutableList;
 
 @BetaApi
-public final class Avg extends Function implements Accumulator {
+public final class Avg extends Accumulator {
   @InternalApi
   Avg(Expr value, boolean distinct) {
     super("avg", ImmutableList.of(value));

google-cloud-firestore/src/main/java/com/google/cloud/firestore/pipeline/expressions/Constant.java

@@ -25,13 +25,17 @@
 import com.google.cloud.firestore.DocumentReference;
 import com.google.cloud.firestore.FieldValue;
 import com.google.cloud.firestore.GeoPoint;
+import com.google.common.collect.ImmutableMap;
 import com.google.firestore.v1.Value;
 import java.util.Arrays;
 import java.util.Date;
 import java.util.Map;
 
 @BetaApi
-public final class Constant implements Expr {
+public final class Constant extends Expr {
+
+  static final Constant NULL = new Constant(null);
+
   private final Object value;
 
   Constant(Object value) {
@@ -85,16 +89,14 @@ public static Constant of(Value value) {
 
   @InternalApi
   public static Constant nullValue() {
-    return new Constant(null);
+    return NULL;
   }
 
   @BetaApi
   static Constant of(Object value) {
     if (value == null) {
-      return new Constant(null);
-    }
-
-    if (value instanceof String) {
+      return NULL;
+    } else if (value instanceof String) {
       return of((String) value);
     } else if (value instanceof Number) {
       return of((Number) value);
@@ -112,23 +114,25 @@ static Constant of(Object value) {
       return of((DocumentReference) value);
     } else if (value instanceof Value) {
       return of((Value) value);
+    } else if (value instanceof Constant) {
+      return (Constant) value;
     } else {
       throw new IllegalArgumentException("Unknown type: " + value);
     }
   }
 
   @BetaApi
-  public static <T> Constant of(Iterable<T> value) {
+  public static Constant of(Iterable<?> value) {
     return new Constant(value);
   }
 
   @BetaApi
-  public static <T> Constant of(T[] value) {
+  public static Constant of(Object[] value) {
     return new Constant(Arrays.asList(value.clone())); // Convert array to list
   }
 
   @BetaApi
-  public static <T> Constant of(Map<String, T> value) {
+  public static Constant of(Map<String, ?> value) {
     return new Constant(value);
   }
 
@@ -137,8 +141,8 @@ public static Constant vector(double[] value) {
     return new Constant(FieldValue.vector(value));
   }
 
-  @InternalApi
-  public Value toProto() {
+  @Override
+  Value toProto() {
     return encodeValue(value);
   }
 }

google-cloud-firestore/src/main/java/com/google/cloud/firestore/pipeline/expressions/Count.java

@@ -22,7 +22,7 @@
 import javax.annotation.Nonnull;
 
 @BetaApi
-public final class Count extends Function implements Accumulator {
+public final class Count extends Accumulator {
   @InternalApi
   Count(@Nonnull Expr value) {
     super("count", ImmutableList.of(value));

google-cloud-firestore/src/main/java/com/google/cloud/firestore/pipeline/expressions/CountIf.java

@@ -21,7 +21,7 @@
 import com.google.common.collect.ImmutableList;
 
 @BetaApi
-public final class CountIf extends Function implements Accumulator {
+public final class CountIf extends Accumulator {
   @InternalApi
   CountIf(Expr value, boolean distinct) {
     super("countif", (value != null) ? ImmutableList.of(value) : ImmutableList.of());