Replace reduce with individual reductions (#1053)

JAVA-4814

Author: katcharov

driver-core/src/main/com/mongodb/client/model/expressions/ArrayExpression.java

@@ -16,7 +16,6 @@
 
 package com.mongodb.client.model.expressions;
 
-import java.util.function.BinaryOperator;
 import java.util.function.Function;
 
 import static com.mongodb.client.model.expressions.Expressions.of;
@@ -51,28 +50,51 @@ public interface ArrayExpression<T extends Expression> extends Expression {
      */
     <R extends Expression> ArrayExpression<R> map(Function<? super T, ? extends R> in);
 
+    IntegerExpression size();
+
+    BooleanExpression any(Function<? super T, BooleanExpression> predicate);
+
+    BooleanExpression all(Function<? super T, BooleanExpression> predicate);
+
+    NumberExpression sum(Function<? super T, ? extends NumberExpression> mapper);
+
+    NumberExpression multiply(Function<? super T, ? extends NumberExpression> mapper);
+
+    T max(T other);
+
+    T min(T other);
+
+    ArrayExpression<T> maxN(IntegerExpression n);
+    ArrayExpression<T> minN(IntegerExpression n);
+
+    StringExpression join(Function<? super T, StringExpression> mapper);
+
+    <R extends Expression> ArrayExpression<R> concat(Function<? super T, ? extends ArrayExpression<? extends R>> mapper);
+
+    <R extends Expression> ArrayExpression<R> union(Function<? super T, ? extends ArrayExpression<? extends R>> mapper);
+
     /**
-     * Performs a reduction on the elements of this array, using the provided
-     * identity value and an associative reducing function, and returns
-     * the reduced value. The initial value must be the identity value for the
-     * reducing function.
+     * user asserts that i is in bounds for the array
      *
-     * @param initialValue the identity for the reducing function
-     * @param in the associative reducing function
-     * @return the reduced value
+     * @param i
+     * @return
      */
-    T reduce(T initialValue, BinaryOperator<T> in);
-
-    IntegerExpression size();
-
     T elementAt(IntegerExpression i);
 
     default T elementAt(final int i) {
         return this.elementAt(of(i));
     }
 
+    /**
+     * user asserts that array is not empty
+     * @return
+     */
     T first();
 
+    /**
+     * user asserts that array is not empty
+     * @return
+     */
     T last();
 
     BooleanExpression contains(T contains);

driver-core/src/main/com/mongodb/client/model/expressions/DocumentExpression.java

@@ -17,7 +17,6 @@
 package com.mongodb.client.model.expressions;
 
 import org.bson.conversions.Bson;
-import org.bson.types.Decimal128;
 
 import java.time.Instant;
 
@@ -47,12 +46,8 @@ default BooleanExpression getBoolean(final String fieldName, final boolean other
 
     NumberExpression getNumber(String fieldName, NumberExpression other);
 
-    default NumberExpression getNumber(final String fieldName, final double other) {
-        return getNumber(fieldName, of(other));
-    }
-
-    default NumberExpression getNumber(final String fieldName, final Decimal128 other) {
-        return getNumber(fieldName, of(other));
+    default NumberExpression getNumber(final String fieldName, final Number other) {
+        return getNumber(fieldName, Expressions.numberToExpression(other));
     }
 
     IntegerExpression getInteger(String fieldName);

driver-core/src/main/com/mongodb/client/model/expressions/MqlExpression.java

@@ -18,6 +18,7 @@
 
 import org.bson.BsonArray;
 import org.bson.BsonDocument;
+import org.bson.BsonInt32;
 import org.bson.BsonString;
 import org.bson.BsonValue;
 import org.bson.codecs.configuration.CodecRegistry;
@@ -385,7 +386,12 @@ public ArrayExpression<T> filter(final Function<? super T, ? extends BooleanExpr
                 .append("cond", extractBsonValue(cr, cond.apply(varThis)))));
     }
 
-    @Override
+    public ArrayExpression<T> sort() {
+        return new MqlExpression<>((cr) -> astDoc("$sortArray", new BsonDocument()
+                .append("input", this.toBsonValue(cr))
+                .append("sortBy", new BsonInt32(1))));
+    }
+
     public T reduce(final T initialValue, final BinaryOperator<T> in) {
         T varThis = variable("$$this");
         T varValue = variable("$$value");
@@ -395,6 +401,77 @@ public T reduce(final T initialValue, final BinaryOperator<T> in) {
                 .append("in", extractBsonValue(cr, in.apply(varValue, varThis)))));
     }
 
+    @Override
+    public BooleanExpression any(final Function<? super T, BooleanExpression> predicate) {
+        MqlExpression<BooleanExpression> array = (MqlExpression<BooleanExpression>) this.map(predicate);
+        return array.reduce(of(false), (a, b) -> a.or(b));
+    }
+
+    @Override
+    public BooleanExpression all(final Function<? super T, BooleanExpression> predicate) {
+        MqlExpression<BooleanExpression> array = (MqlExpression<BooleanExpression>) this.map(predicate);
+        return array.reduce(of(true), (a, b) -> a.and(b));
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public NumberExpression sum(final Function<? super T, ? extends NumberExpression> mapper) {
+        // no sum that returns IntegerExpression, both have same erasure
+        MqlExpression<NumberExpression> array = (MqlExpression<NumberExpression>) this.map(mapper);
+        return array.reduce(of(0), (a, b) -> a.add(b));
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public NumberExpression multiply(final Function<? super T, ? extends NumberExpression> mapper) {
+        MqlExpression<NumberExpression> array = (MqlExpression<NumberExpression>) this.map(mapper);
+        return array.reduce(of(0), (NumberExpression a, NumberExpression b) -> a.multiply(b));
+    }
+
+    @Override
+    public T max(final T other) {
+        return this.size().eq(of(0)).cond(other, this.maxN(of(1)).first());
+    }
+
+    @Override
+    public T min(final T other) {
+        return this.size().eq(of(0)).cond(other, this.minN(of(1)).first());
+    }
+
+    @Override
+    public ArrayExpression<T> maxN(final IntegerExpression n) {
+        return newMqlExpression((CodecRegistry cr) -> astDoc("$maxN", new BsonDocument()
+                .append("input", extractBsonValue(cr, this))
+                .append("n", extractBsonValue(cr, n))));
+    }
+
+    @Override
+    public ArrayExpression<T> minN(final IntegerExpression n) {
+        return newMqlExpression((CodecRegistry cr) -> astDoc("$minN", new BsonDocument()
+                .append("input", extractBsonValue(cr, this))
+                .append("n", extractBsonValue(cr, n))));
+    }
+
+    @Override
+    public StringExpression join(final Function<? super T, StringExpression> mapper) {
+        MqlExpression<StringExpression> array = (MqlExpression<StringExpression>) this.map(mapper);
+        return array.reduce(of(""), (a, b) -> a.concat(b));
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public <R extends Expression> ArrayExpression<R> concat(final Function<? super T, ? extends ArrayExpression<? extends R>> mapper) {
+        MqlExpression<ArrayExpression<R>> array = (MqlExpression<ArrayExpression<R>>) this.map(mapper);
+        return array.reduce(Expressions.ofArray(), (a, b) -> a.concat(b));
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public <R extends Expression> ArrayExpression<R> union(final Function<? super T, ? extends ArrayExpression<? extends R>> mapper) {
+        MqlExpression<ArrayExpression<R>> array = (MqlExpression<ArrayExpression<R>>) this.map(mapper);
+        return array.reduce(Expressions.ofArray(), (a, b) -> a.union(b));
+    }
+
     @Override
     public IntegerExpression size() {
         return new MqlExpression<>(astWrapped("$size"));