feat: add functions as UDF input types

ksqldb-common/src/main/java/io/confluent/ksql/function/types/LambdaType.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2021 Confluent Inc.
+ *
+ * Licensed under the Confluent Community License (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.confluent.io/confluent-community-license
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OF ANY KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+
+package io.confluent.ksql.function.types;
+
+import com.google.common.collect.ImmutableList;
+import java.util.List;
+import java.util.Objects;
+
+public final class LambdaType extends ObjectType {
+
+  private final ImmutableList<ParamType> inputTypes;
+  private final ParamType returnType;
+
+  private LambdaType(
+      final List<ParamType> inputTypes,
+      final ParamType returnType
+  ) {
+    this.inputTypes = ImmutableList.copyOf(
+        Objects.requireNonNull(inputTypes, "inputTypes"));
+    this.returnType = Objects.requireNonNull(returnType, "returnType");
+  }
+
+  public static LambdaType of(
+      final List<ParamType> inputTypes,
+      final ParamType returnType
+  ) {
+    return new LambdaType(inputTypes, returnType);
+  }
+
+  public List<ParamType> inputTypes() {
+    return inputTypes;
+  }
+
+  public ParamType returnType() {
+    return returnType;
+  }
+
+  @Override
+  public boolean equals(final Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    final LambdaType lambdaType = (LambdaType) o;
+    return Objects.equals(inputTypes, lambdaType.inputTypes)
+        && Objects.equals(returnType, lambdaType.returnType);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(inputTypes, returnType);
+  }
+
+  @Override
+  public String toString() {
+    return "LAMBDA<" + inputTypes + ", " + returnType + ">";
+  }
+}

ksqldb-common/src/main/java/io/confluent/ksql/util/AppInfo.java

@@ -42,9 +42,7 @@ public final class AppInfo {
       final Properties props = new Properties();
       try (InputStream resourceAsStream = AppInfo.class.getResourceAsStream(
           "/git.properties")) {
-        if (resourceAsStream != null) {
-          props.load(resourceAsStream);
-        }
+        props.load(resourceAsStream);
       }
       commitId = props.getProperty("git.commit.id", commitId).trim();
     } catch (final Exception e) {

ksqldb-engine/src/main/java/io/confluent/ksql/engine/rewrite/ExpressionTreeRewriter.java

@@ -74,7 +74,7 @@
  * @param <C> A context type to be passed through to the plugin.
  */
 public final class ExpressionTreeRewriter<C> {
-  
+
   public static final class Context<C> {
     private final C context;
     private final ExpressionVisitor<Expression, C> rewriter;

ksqldb-engine/src/main/java/io/confluent/ksql/function/UdafTypes.java

@@ -17,6 +17,7 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
+import io.confluent.ksql.execution.codegen.helpers.TriFunction;
 import io.confluent.ksql.execution.function.UdfUtil;
 import io.confluent.ksql.function.types.ParamType;
 import io.confluent.ksql.name.FunctionName;
@@ -34,6 +35,8 @@
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
+import java.util.function.BiFunction;
+import java.util.function.Function;
 import org.apache.kafka.connect.data.Struct;
 
 class UdafTypes {
@@ -53,6 +56,9 @@ class UdafTypes {
       .add(List.class)
       .add(Map.class)
       .add(Timestamp.class)
+      .add(Function.class)
+      .add(BiFunction.class)
+      .add(TriFunction.class)
       .build();
 
   private final Type inputType;

ksqldb-engine/src/main/java/io/confluent/ksql/function/udf/array/ArrayTransform.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2021 Confluent Inc.
+ *
+ * Licensed under the Confluent Community License (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.confluent.io/confluent-community-license
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OF ANY KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+
+package io.confluent.ksql.function.udf.array;
+
+import io.confluent.ksql.function.FunctionCategory;
+import io.confluent.ksql.function.udf.Udf;
+import io.confluent.ksql.function.udf.UdfDescription;
+import io.confluent.ksql.function.udf.UdfParameter;
+import io.confluent.ksql.util.KsqlConstants;
+import java.util.List;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+/**
+ * Transform an array with a function
+ */
+@SuppressWarnings("MethodMayBeStatic") // UDF methods can not be static.
+@UdfDescription(
+    name = "array_transform",
+    category = FunctionCategory.ARRAY,
+    description = "Apply a function to each element in an array. " 
+        + "The transformed array is returned.",
+    author = KsqlConstants.CONFLUENT_AUTHOR
+)
+public class ArrayTransform {
+
+  @Udf
+  public <T, R> List<R> arrayTransform(
+      @UdfParameter(description = "The array") final List<T> array,
+      @UdfParameter(description = "The lambda function") final Function<T, R> function
+  ) {
+    if (array == null) {
+      return null;
+    }
+    return array.stream().map(item -> {
+      if (item == null) {
+        return null;
+      }
+      return function.apply(item);
+    }).collect(Collectors.toList());
+  }
+}

ksqldb-engine/src/main/java/io/confluent/ksql/function/udf/map/MapTransform.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2021 Confluent Inc.
+ *
+ * Licensed under the Confluent Community License (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.confluent.io/confluent-community-license
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OF ANY KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+
+package io.confluent.ksql.function.udf.map;
+
+import io.confluent.ksql.function.FunctionCategory;
+import io.confluent.ksql.function.udf.Udf;
+import io.confluent.ksql.function.udf.UdfDescription;
+import io.confluent.ksql.function.udf.UdfParameter;
+import io.confluent.ksql.util.KsqlConstants;
+import java.util.Map;
+import java.util.function.BiFunction;
+import java.util.stream.Collectors;
+
+/**
+ * Transform a map's key and values using two lambda functions
+ */
+@UdfDescription(
+    name = "map_transform",
+    category = FunctionCategory.MAP,
+    description = "Apply one function to each key and " 
+        + "one function to each value of a map. " 
+        + "The two arguments for each function are in order: key, value. " 
+        + "The first function provided will be applied to each key and the " 
+        + "second one applied to each value. "
+        + "The transformed map is returned.",
+    author = KsqlConstants.CONFLUENT_AUTHOR
+)
+public class MapTransform {
+
+  @Udf
+  public <K,V,R,T> Map<R,T> mapTransform(
+      @UdfParameter(description = "The map") final Map<K, V> map,
+      @UdfParameter(description = "The key lambda function") final BiFunction<K, V, R> biFunction1,
+      @UdfParameter(description = "The value lambda function") final BiFunction<K, V, T> biFunction2
+  ) {
+    if (map == null) {
+      return null;
+    }
+
+    return map.entrySet()
+        .stream()
+        .collect(Collectors.toMap(
+            entry -> biFunction1.apply(entry.getKey(), entry.getValue()),
+            entry -> biFunction2.apply(entry.getKey(), entry.getValue())));
+  }
+}

ksqldb-engine/src/main/java/io/confluent/ksql/function/udf/map/ReduceMap.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2021 Confluent Inc.
+ *
+ * Licensed under the Confluent Community License (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.confluent.io/confluent-community-license
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OF ANY KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+
+package io.confluent.ksql.function.udf.map;
+
+import io.confluent.ksql.execution.codegen.helpers.TriFunction;
+import io.confluent.ksql.function.FunctionCategory;
+import io.confluent.ksql.function.udf.Udf;
+import io.confluent.ksql.function.udf.UdfDescription;
+import io.confluent.ksql.function.udf.UdfParameter;
+import io.confluent.ksql.util.KsqlConstants;
+import java.util.Map;
+import java.util.Map.Entry;
+
+/**
+ * Reduce a map using an initial state and function
+ */
+@UdfDescription(
+    name = "map_reduce",
+    category = FunctionCategory.MAP,
+    description = "Reduce the input map down to a single value " 
+        + "using an initial state and a function. " 
+        + "The initial state (s) is passed into the scope of the function. " 
+        + "Each invocation returns a new value for s, " 
+        + "which the next invocation will receive. "  
+        + "The final value for s is returned."
+        + "The three arguments for the function are in order: key, value, state.",
+    author = KsqlConstants.CONFLUENT_AUTHOR
+)
+public class ReduceMap {
+
+  @Udf
+  public <K,V,S> S reduceMap(
+      @UdfParameter(description = "The map") final Map<K, V> map,
+      @UdfParameter(description = "The initial state") final S initialState,
+      @UdfParameter(description = "The reduce function") final TriFunction<K, V, S, S> triFunction
+  ) {
+    if (map == null) {
+      return null;
+    }
+
+    S state = initialState;
+    for (Entry<K, V> entry : map.entrySet()) {
+      state = triFunction.apply(entry.getKey(), entry.getValue(), state);
+    }
+    return state;
+  }
+}