Implement switch expression

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

@@ -112,4 +112,8 @@ default ArrayExpression<T> slice(final int start, final int length) {
     ArrayExpression<T> union(ArrayExpression<? extends T> set);
 
     ArrayExpression<T> distinct();
+
+    <R extends Expression> R passArrayTo(Function<? super ArrayExpression<T>, ? extends R> f);
+
+    <R extends Expression> R switchArrayOn(Function<Branches<ArrayExpression<T>>, ? extends BranchesTerminal<ArrayExpression<T>, ? extends R>> on);
 }

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

@@ -16,6 +16,8 @@
 
 package com.mongodb.client.model.expressions;
 
+import java.util.function.Function;
+
 /**
  * Expresses a boolean value.
  */
@@ -58,4 +60,8 @@ public interface BooleanExpression extends Expression {
      * @param <T> The type of the resulting expression.
      */
     <T extends Expression> T cond(T left, T right);
+
+    <R extends Expression> R passBooleanTo(Function<? super BooleanExpression, ? extends R> f);
+
+    <R extends Expression> R switchBooleanOn(Function<Branches<BooleanExpression>, ? extends BranchesTerminal<BooleanExpression, ? extends R>> on);
 }

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

@@ -0,0 +1,97 @@
+/*
+ * Copyright 2008-present MongoDB, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.mongodb.client.model.expressions;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Function;
+
+public final class Branches<T extends Expression> {
+
+    Branches() {
+    }
+
+    private static <T extends Expression, R extends Expression> BranchesIntermediary<T, R> with(final Function<T, SwitchCase<R>> switchCase) {
+        List<Function<T, SwitchCase<R>>> v = new ArrayList<>();
+        v.add(switchCase);
+        return new BranchesIntermediary<>(v);
+    }
+
+    private static <T extends Expression> MqlExpression<?> mqlEx(final T value) {
+        return (MqlExpression<?>) value;
+    }
+
+    // is fn
+
+    public <T extends Expression, R extends Expression> BranchesIntermediary<T, R> is(final Function<? super T, BooleanExpression> o, final Function<? super T, ? extends R> r) {
+        return with(value -> new SwitchCase<>(o.apply(value), r.apply(value)));
+    }
+
+    // eq lt lte
+
+    public <R extends Expression> BranchesIntermediary<T, R> eq(final T v, final Function<? super T, ? extends R> r) {
+        return is(value -> value.eq(v), r);
+    }
+
+    public <R extends Expression> BranchesIntermediary<T, R> lt(final T v, final Function<? super T, ? extends R> r) {
+        return is(value -> value.lt(v), r);
+    }
+
+    public <R extends Expression> BranchesIntermediary<T, R> lte(final T v, final Function<? super T, ? extends R> r) {
+        return is(value -> value.lte(v), r);
+    }
+
+    // is type
+
+    public <R extends Expression> BranchesIntermediary<T, R> isBoolean(final Function<? super BooleanExpression, ? extends R> r) {
+        return is(v -> mqlEx(v).isBoolean(), v -> r.apply((BooleanExpression) v));
+    }
+
+    public <R extends Expression> BranchesIntermediary<T, R> isNumber(final Function<? super NumberExpression, ? extends R> r) {
+        return is(v -> mqlEx(v).isNumber(), v -> r.apply((NumberExpression) v));
+    }
+
+    public <R extends Expression> BranchesIntermediary<T, R> isInteger(final Function<? super IntegerExpression, ? extends R> r) {
+        return is(v -> mqlEx(v).isInteger(), v -> r.apply((IntegerExpression) v));
+    }
+
+    public <R extends Expression> BranchesIntermediary<T, R> isString(final Function<? super StringExpression, ? extends R> r) {
+        return is(v -> mqlEx(v).isString(), v -> r.apply((StringExpression) v));
+    }
+
+    public <R extends Expression> BranchesIntermediary<T, R> isDate(final Function<? super DateExpression, ? extends R> r) {
+        return is(v -> mqlEx(v).isDate(), v -> r.apply((DateExpression) v));
+    }
+
+    @SuppressWarnings("unchecked")
+    public <R extends Expression, Q extends Expression> BranchesIntermediary<T, R> isArray(final Function<? super ArrayExpression<Q>, ? extends R> r) {
+        return is(v -> mqlEx(v).isArray(), v -> r.apply((ArrayExpression<Q>) v));
+    }
+
+    public <R extends Expression> BranchesIntermediary<T, R> isDocument(final Function<? super DocumentExpression, ? extends R> r) {
+        return is(v -> mqlEx(v).isDocumentOrMap(), v -> r.apply((DocumentExpression) v));
+    }
+
+    @SuppressWarnings("unchecked")
+    public <R extends Expression, Q extends Expression> BranchesIntermediary<T, R> isMap(final Function<? super MapExpression<Q>, ? extends R> r) {
+        return is(v -> mqlEx(v).isDocumentOrMap(), v -> r.apply((MapExpression<Q>) v));
+    }
+
+    public <R extends Expression> BranchesIntermediary<T, R> isNull(final Function<? super Expression, ? extends R> r) {
+        return is(v -> mqlEx(v).isNull(), v -> r.apply(v));
+    }
+}

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

@@ -0,0 +1,102 @@
+/*
+ * Copyright 2008-present MongoDB, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.mongodb.client.model.expressions;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Function;
+
+public final class BranchesIntermediary<T extends Expression, R extends Expression> extends BranchesTerminal<T, R> {
+    BranchesIntermediary(final List<Function<T, SwitchCase<R>>> branches) {
+        super(branches, null);
+    }
+
+    private BranchesIntermediary<T, R> with(final Function<T, SwitchCase<R>> switchCase) {
+        List<Function<T, SwitchCase<R>>> v = new ArrayList<>(this.getBranches());
+        v.add(switchCase);
+        return new BranchesIntermediary<>(v);
+    }
+
+    private static <T extends Expression> MqlExpression<?> mqlEx(final T value) {
+        return (MqlExpression<?>) value;
+    }
+
+    // is fn
+
+    public BranchesIntermediary<T, R> is(final Function<? super T, BooleanExpression> o, final Function<? super T, ? extends R> r) {
+        return this.with(value -> new SwitchCase<>(o.apply(value), r.apply(value)));
+    }
+
+    // eq lt lte
+
+    public BranchesIntermediary<T, R> eq(final T v, final Function<? super T, ? extends R> r) {
+        return is(value -> value.eq(v), r);
+    }
+
+    public BranchesIntermediary<T, R> lt(final T v, final Function<? super T, ? extends R> r) {
+        return is(value -> value.lt(v), r);
+    }
+
+    public BranchesIntermediary<T, R> lte(final T v, final Function<? super T, ? extends R> r) {
+        return is(value -> value.lte(v), r);
+    }
+
+    // is type
+
+    public BranchesIntermediary<T, R> isBoolean(final Function<? super BooleanExpression, ? extends R> r) {
+        return is(v -> mqlEx(v).isBoolean(), v -> r.apply((BooleanExpression) v));
+    }
+
+    public BranchesIntermediary<T, R> isNumber(final Function<? super NumberExpression, ? extends R> r) {
+        return is(v -> mqlEx(v).isNumber(), v -> r.apply((NumberExpression) v));
+    }
+
+    public BranchesIntermediary<T, R> isInteger(final Function<? super IntegerExpression, ? extends R> r) {
+        return is(v -> mqlEx(v).isInteger(), v -> r.apply((IntegerExpression) v));
+    }
+
+    public BranchesIntermediary<T, R> isString(final Function<? super StringExpression, ? extends R> r) {
+        return is(v -> mqlEx(v).isString(), v -> r.apply((StringExpression) v));
+    }
+
+    public BranchesIntermediary<T, R> isDate(final Function<? super DateExpression, ? extends R> r) {
+        return is(v -> mqlEx(v).isDate(), v -> r.apply((DateExpression) v));
+    }
+
+    @SuppressWarnings("unchecked")
+    public <Q extends Expression> BranchesIntermediary<T, R> isArray(final Function<? super ArrayExpression<Q>, ? extends R> r) {
+        return is(v -> mqlEx(v).isArray(), v -> r.apply((ArrayExpression<Q>) v));
+    }
+
+    public BranchesIntermediary<T, R> isDocument(final Function<? super DocumentExpression, ? extends R> r) {
+        return is(v -> mqlEx(v).isDocumentOrMap(), v -> r.apply((DocumentExpression) v));
+    }
+
+    @SuppressWarnings("unchecked")
+    public <Q extends Expression> BranchesIntermediary<T, R> isMap(final Function<? super MapExpression<Q>, ? extends R> r) {
+        return is(v -> mqlEx(v).isDocumentOrMap(), v -> r.apply((MapExpression<Q>) v));
+    }
+
+    public BranchesIntermediary<T, R> isNull(final Function<? super Expression, ? extends R> r) {
+        return is(v -> mqlEx(v).isNull(), v -> r.apply(v));
+    }
+
+    public BranchesTerminal<T, R> defaults(final Function<? super T, ? extends R> r) {
+        return this.withDefault(value -> r.apply(value));
+    }
+
+}

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

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2008-present MongoDB, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.mongodb.client.model.expressions;
+
+import com.mongodb.lang.Nullable;
+
+import java.util.List;
+import java.util.function.Function;
+
+public class BranchesTerminal<T extends Expression, R extends Expression> {
+
+    private final List<Function<T, SwitchCase<R>>> branches;
+
+    private final Function<T, R> defaults;
+
+    BranchesTerminal(final List<Function<T, SwitchCase<R>>> branches, @Nullable final Function<T, R> defaults) {
+        this.branches = branches;
+        this.defaults = defaults;
+    }
+
+    protected BranchesTerminal<T, R> withDefault(final Function<T, R> defaults) {
+        return new BranchesTerminal<>(branches, defaults);
+    }
+
+    protected List<Function<T, SwitchCase<R>>> getBranches() {
+        return branches;
+    }
+
+    @Nullable
+    protected Function<T, R> getDefaults() {
+        return defaults;
+    }
+}

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

@@ -16,6 +16,8 @@
 
 package com.mongodb.client.model.expressions;
 
+import java.util.function.Function;
+
 /**
  * Expresses a date value.
  */
@@ -33,4 +35,6 @@ public interface DateExpression extends Expression {
 
     StringExpression asString(StringExpression timezone, StringExpression format);
 
+    <R extends Expression> R passDateTo(Function<? super DateExpression, ? extends R> f);
+    <R extends Expression> R switchDateOn(Function<Branches<DateExpression>, ? extends BranchesTerminal<DateExpression, ? extends R>> on);
 }

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

@@ -19,6 +19,7 @@
 import org.bson.conversions.Bson;
 
 import java.time.Instant;
+import java.util.function.Function;
 
 import static com.mongodb.client.model.expressions.Expressions.of;
 import static com.mongodb.client.model.expressions.Expressions.ofMap;
@@ -100,4 +101,7 @@ default <T extends Expression> MapExpression<T> getMap(final String fieldName, f
     DocumentExpression merge(DocumentExpression other);
 
     MapExpression<Expression> asMap();
+
+    <R extends Expression> R passDocumentTo(Function<? super DocumentExpression, ? extends R> f);
+    <R extends Expression> R switchDocumentOn(Function<Branches<DocumentExpression>, ? extends BranchesTerminal<DocumentExpression, ? extends R>> on);
 }

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

@@ -18,6 +18,8 @@
 
 import com.mongodb.annotations.Evolving;
 
+import java.util.function.Function;
+
 /**
  * Expressions express values that may be represented in (or computations that
  * may be performed within) a MongoDB server. Each expression evaluates to some
@@ -114,4 +116,9 @@ public interface Expression {
     <T extends Expression> MapExpression<T> isMapOr(MapExpression<? extends T> other);
 
     StringExpression asString();
+
+    <R extends Expression> R passTo(Function<? super Expression, ? extends R> f);
+
+    <R extends Expression> R switchOn(Function<Branches<Expression>, ? extends BranchesTerminal<Expression, ? extends R>> on);
+
 }

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

@@ -16,6 +16,8 @@
 
 package com.mongodb.client.model.expressions;
 
+import java.util.function.Function;
+
 /**
  * Expresses an integer value.
  */
@@ -42,4 +44,7 @@ default IntegerExpression subtract(final int subtract) {
     IntegerExpression min(IntegerExpression i);
 
     IntegerExpression abs();
+
+    <R extends Expression> R passIntegerTo(Function<? super IntegerExpression, ? extends R> f);
+    <R extends Expression> R switchIntegerOn(Function<Branches<IntegerExpression>, ? extends BranchesTerminal<IntegerExpression, ? extends R>> on);
 }

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

@@ -16,6 +16,8 @@
 
 package com.mongodb.client.model.expressions;
 
+import java.util.function.Function;
+
 import static com.mongodb.client.model.expressions.Expressions.of;
 
 public interface MapExpression<T extends Expression> extends Expression {
@@ -57,4 +59,7 @@ default MapExpression<T> unset(final String key) {
     ArrayExpression<EntryExpression<T>> entrySet();
 
     <R extends DocumentExpression> R asDocument();
+
+    <R extends Expression> R passMapTo(Function<? super MapExpression<T>, ? extends R> f);
+    <R extends Expression> R switchMapOn(Function<Branches<MapExpression<T>>, ? extends BranchesTerminal<MapExpression<T>, ? extends R>> on);
 }