content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 org.apache.beam.sdk.extensions.sql.impl;
  
  import static org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.util.Static.RESOURCE;
  
  import java.lang.reflect.Constructor;
  import java.lang.reflect.Method;
  import java.lang.reflect.Modifier;
  import java.lang.reflect.Type;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  import org.apache.beam.sdk.extensions.sql.impl.utils.CalciteUtils;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.adapter.enumerable.CallImplementor;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.adapter.enumerable.NullPolicy;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.adapter.enumerable.ReflectiveCallNotNullImplementor;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.adapter.enumerable.RexImpTable;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.adapter.enumerable.RexToLixTranslator;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.avatica.util.ByteString;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.linq4j.function.SemiStrict;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.linq4j.function.Strict;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.linq4j.tree.Expression;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.linq4j.tree.Expressions;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rel.type.RelDataType;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rel.type.RelDataTypeFactory;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rex.RexCall;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.schema.Function;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.schema.ImplementableFunction;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.schema.ScalarFunction;
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.sql.SqlOperatorBinding;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableMultimap;
  
  /**
   * Beam-customized version from {@link
   * org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.schema.impl.ScalarFunctionImpl} , to
   * address BEAM-5921.
   */
  @SuppressWarnings({
    "rawtypes", // TODO(https://github.com/apache/beam/issues/20447)
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class ScalarFunctionImpl extends UdfImplReflectiveFunctionBase
      implements ScalarFunction, ImplementableFunction {
  
    private final CallImplementor implementor;
    private final String jarPath;
  
    protected ScalarFunctionImpl(Method method, CallImplementor implementor, String jarPath) {
      super(method);
      this.implementor = implementor;
      this.jarPath = jarPath;
    }
  
    protected ScalarFunctionImpl(Method method, CallImplementor implementor) {
      this(method, implementor, "");
    }
  
    /**
     * Optional Beam filesystem path to the jar containing the bytecode for this function. Empty if
     * the function is assumed to already be on the classpath.
     */
    public String getJarPath() {
      return jarPath;
    }
  
    /**
     * Creates {@link org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.schema.Function} for
     * each method in a given class.
     */
    public static ImmutableMultimap<String, Function> createAll(Class<?> clazz) {
      final ImmutableMultimap.Builder<String, Function> builder = ImmutableMultimap.builder();
      for (Method method : clazz.getMethods()) {
        if (method.getDeclaringClass() == Object.class) {
          continue;
        }
        if (!Modifier.isStatic(method.getModifiers()) && !classHasPublicZeroArgsConstructor(clazz)) {
          continue;
        }
        final Function function = create(method);
        builder.put(method.getName(), function);
      }
      return builder.build();
    }
  
    /**
     * Creates {@link org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.schema.Function} from
     * given method. When {@code eval} method does not suit, {@code null} is returned.
     *
     * @param method method that is used to implement the function
     * @return created {@link Function} or null
     */
    public static Function create(Method method) {
      return create(method, "");
    }
  
    /**
     * Creates {@link org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.schema.Function} from
     * given method. When {@code eval} method does not suit, {@code null} is returned.
     *
     * @param method method that is used to implement the function
     * @param jarPath Path to jar that contains the method.
     * @return created {@link Function} or null
     */
    public static Function create(Method method, String jarPath) {
      validateMethod(method);
      CallImplementor implementor = createImplementor(method);
      return new ScalarFunctionImpl(method, implementor, jarPath);
    }
  
    protected static void validateMethod(Method method) {
      if (!Modifier.isStatic(method.getModifiers())) {
        Class clazz = method.getDeclaringClass();
        if (!classHasPublicZeroArgsConstructor(clazz)) {
          throw RESOURCE.requireDefaultConstructor(clazz.getName()).ex();
        }
      }
      if (method.getExceptionTypes().length != 0) {
        throw new RuntimeException(method.getName() + " must not throw checked exception");
      }
    }
  
    @Override
    public RelDataType getReturnType(RelDataTypeFactory typeFactory) {
      return CalciteUtils.sqlTypeWithAutoCast(typeFactory, method.getGenericReturnType());
    }
  
    @Override
    public CallImplementor getImplementor() {
      return implementor;
    }
  
    /**
     * Version of {@link ReflectiveCallNotNullImplementor} that does parameter conversion for Beam
     * UDFs.
     */
    private static class ScalarReflectiveCallNotNullImplementor
        extends ReflectiveCallNotNullImplementor {
      ScalarReflectiveCallNotNullImplementor(Method method) {
        super(method);
      }
  
      private static List<Expression> translate(List<Type> types, List<Expression> expressions) {
        // https://issues.apache.org/jira/browse/BEAM-8241
        // In user defined functions Calcite allows variants with fewer arguments than Beam defined.
        Preconditions.checkArgument(
            types.size() >= expressions.size(), "types.size() < expressions.size()");
  
        final List<Expression> translated = new ArrayList<>();
        for (int i = 0; i < expressions.size(); i++) {
          // TODO: [https://github.com/apache/beam/issues/19825] Add support for user defined function
          // with var-arg
          // Ex: types: [String[].class], expression: [param1, param2, ...]
          translated.add(translate(types.get(i), expressions.get(i)));
        }
  
        return translated;
      }
  
      private static Expression translate(Type type, Expression expression) {
        // NB: base class is called ReflectiveCallNotNullImplementor, but nulls are possible
        //
        // Calcite infers our UDF parameters as nullable, and WILL pass nullable expressions to this
        // method. We could revisit this by explicitly asking users to add @Nullable annotation
        // to UDF parameters, and not treating them as nullable by default, and then we can better
        // determine if expression is possibly nullable by using reflection.
  
        if (type == byte[].class && expression.type == ByteString.class) {
          return Expressions.condition(
              Expressions.equal(expression, Expressions.constant(null)),
              Expressions.constant(null),
              Expressions.call(expression, "getBytes"));
        }
  
        return expression;
      }
  
      @Override
      public Expression implement(
          RexToLixTranslator translator, RexCall call, List<Expression> translatedOperands) {
        final List<Expression> translated =
            translate(Arrays.asList(method.getParameterTypes()), translatedOperands);
  
        // delegate to the underlying implementation to do the rest of translations
        return super.implement(translator, call, translated);
      }
    }
  
    protected static CallImplementor createImplementor(Method method) {
      final NullPolicy nullPolicy = getNullPolicy(method);
      return RexImpTable.createImplementor(
          new ScalarReflectiveCallNotNullImplementor(method), nullPolicy, false);
    }
  
    private static NullPolicy getNullPolicy(Method m) {
      if (m.getAnnotation(Strict.class) != null) {
        return NullPolicy.STRICT;
      } else if (m.getAnnotation(SemiStrict.class) != null) {
        return NullPolicy.SEMI_STRICT;
      } else if (m.getDeclaringClass().getAnnotation(Strict.class) != null) {
        return NullPolicy.STRICT;
      } else if (m.getDeclaringClass().getAnnotation(SemiStrict.class) != null) {
        return NullPolicy.SEMI_STRICT;
      } else {
        return NullPolicy.NONE;
      }
    }
  
    public RelDataType getReturnType(RelDataTypeFactory typeFactory, SqlOperatorBinding opBinding) {
      // Strict and semi-strict functions can return null even if their Java
      // functions return a primitive type. Because when one of their arguments
      // is null, they won't even be called.
      final RelDataType returnType = getReturnType(typeFactory);
      switch (getNullPolicy(method)) {
        case STRICT:
          for (RelDataType type : opBinding.collectOperandTypes()) {
            if (type.isNullable()) {
              return typeFactory.createTypeWithNullability(returnType, true);
            }
          }
          break;
        case SEMI_STRICT:
          return typeFactory.createTypeWithNullability(returnType, true);
        default:
          break;
      }
      return returnType;
    }
  
    /**
     * Verifies if given class has public constructor with zero arguments.
     *
     * @param clazz class to verify
     * @return true if given class has public constructor with zero arguments
     */
    static boolean classHasPublicZeroArgsConstructor(Class<?> clazz) {
      for (Constructor<?> constructor : clazz.getConstructors()) {
        if (constructor.getParameterTypes().length == 0
            && Modifier.isPublic(constructor.getModifiers())) {
          return true;
        }
      }
      return false;
    }
  }
  
  // End ScalarFunctionImpl.java
  