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.calcite.adapter.enumerable;
  
  import org.apache.calcite.DataContext;
  import org.apache.calcite.adapter.java.JavaTypeFactory;
  import org.apache.calcite.linq4j.tree.BlockBuilder;
  import org.apache.calcite.linq4j.tree.Expression;
  import org.apache.calcite.linq4j.tree.Expressions;
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.TableFunctionScan;
  import org.apache.calcite.rel.metadata.RelColumnMapping;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rex.RexCall;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.schema.QueryableTable;
  import org.apache.calcite.schema.impl.TableFunctionImpl;
  import org.apache.calcite.sql.SqlWindowTableFunction;
  import org.apache.calcite.sql.validate.SqlConformance;
  import org.apache.calcite.sql.validate.SqlConformanceEnum;
  import org.apache.calcite.sql.validate.SqlUserDefinedTableFunction;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.lang.reflect.Method;
  import java.lang.reflect.Type;
  import java.util.List;
  import java.util.Set;
  
  /** Implementation of {@link org.apache.calcite.rel.core.TableFunctionScan} in
   * {@link org.apache.calcite.adapter.enumerable.EnumerableConvention enumerable calling convention}. */
  public class EnumerableTableFunctionScan extends TableFunctionScan
      implements EnumerableRel {
  
    public EnumerableTableFunctionScan(RelOptCluster cluster,
        RelTraitSet traits, List<RelNode> inputs, @Nullable Type elementType,
        RelDataType rowType, RexNode call,
        @Nullable Set<RelColumnMapping> columnMappings) {
      super(cluster, traits, inputs, call, elementType, rowType,
          columnMappings);
    }
  
    @Override public EnumerableTableFunctionScan copy(
        RelTraitSet traitSet,
        List<RelNode> inputs,
        RexNode rexCall,
        @Nullable Type elementType,
        RelDataType rowType,
        @Nullable Set<RelColumnMapping> columnMappings) {
      return new EnumerableTableFunctionScan(getCluster(), traitSet, inputs,
          elementType, rowType, rexCall, columnMappings);
    }
  
    @Override public Result implement(EnumerableRelImplementor implementor, Prefer pref) {
      if (isImplementorDefined((RexCall) getCall())) {
        return tvfImplementorBasedImplement(implementor, pref);
      } else {
        return defaultTableFunctionImplement(implementor, pref);
      }
    }
  
    private static boolean isImplementorDefined(RexCall call) {
      if (call.getOperator() instanceof SqlWindowTableFunction
          && RexImpTable.INSTANCE.get((SqlWindowTableFunction) call.getOperator()) != null) {
        return true;
      }
      return false;
    }
  
    private boolean isQueryable() {
      if (!(getCall() instanceof RexCall)) {
        return false;
      }
      final RexCall call = (RexCall) getCall();
      if (!(call.getOperator() instanceof SqlUserDefinedTableFunction)) {
        return false;
      }
      final SqlUserDefinedTableFunction udtf =
          (SqlUserDefinedTableFunction) call.getOperator();
      if (!(udtf.getFunction() instanceof TableFunctionImpl)) {
        return false;
      }
      final TableFunctionImpl tableFunction =
          (TableFunctionImpl) udtf.getFunction();
      final Method method = tableFunction.method;
      return QueryableTable.class.isAssignableFrom(method.getReturnType());
    }
  
    private Result defaultTableFunctionImplement(
        EnumerableRelImplementor implementor,
        @SuppressWarnings("unused") Prefer pref) { // TODO: remove or use
      BlockBuilder bb = new BlockBuilder();
      // Non-array user-specified types are not supported yet
      final JavaRowFormat format;
      Type elementType = getElementType();
      if (elementType == null) {
        format = JavaRowFormat.ARRAY;
      } else if (getRowType().getFieldCount() == 1 && isQueryable()) {
        format = JavaRowFormat.SCALAR;
      } else if (elementType instanceof Class
          && Object[].class.isAssignableFrom((Class<?>) elementType)) {
        format = JavaRowFormat.ARRAY;
      } else {
        format = JavaRowFormat.CUSTOM;
      }
      final PhysType physType =
          PhysTypeImpl.of(implementor.getTypeFactory(), getRowType(), format,
              false);
      RexToLixTranslator t =
          RexToLixTranslator.forAggregation(
              (JavaTypeFactory) getCluster().getTypeFactory(),
              bb, null, implementor.getConformance());
      t = t.setCorrelates(implementor.allCorrelateVariables);
      bb.add(Expressions.return_(null, t.translate(getCall())));
      return implementor.result(physType, bb.toBlock());
    }
  
    private Result tvfImplementorBasedImplement(
        EnumerableRelImplementor implementor, Prefer pref) {
      final JavaTypeFactory typeFactory = implementor.getTypeFactory();
      final BlockBuilder builder = new BlockBuilder();
      final EnumerableRel child = (EnumerableRel) getInputs().get(0);
      final Result result =
          implementor.visitChild(this, 0, child, pref);
      final PhysType physType =
          PhysTypeImpl.of(typeFactory, getRowType(), pref.prefer(result.format));
      final Expression inputEnumerable =
          builder.append("_input", result.block, false);
      final SqlConformance conformance =
          (SqlConformance) implementor.map.getOrDefault("_conformance",
              SqlConformanceEnum.DEFAULT);
  
      builder.add(
          RexToLixTranslator.translateTableFunction(
              typeFactory,
              conformance,
              builder,
              DataContext.ROOT,
              (RexCall) getCall(),
              inputEnumerable,
              result.physType,
              physType));
  
      return implementor.result(physType, builder.toBlock());
    }
  }
  