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/*
 * 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.geode.rel;

import org.apache.calcite.adapter.enumerable.EnumerableRel;
import org.apache.calcite.adapter.enumerable.EnumerableRelImplementor;
import org.apache.calcite.adapter.enumerable.JavaRowFormat;
import org.apache.calcite.adapter.enumerable.PhysType;
import org.apache.calcite.adapter.enumerable.PhysTypeImpl;
import org.apache.calcite.adapter.geode.rel.GeodeRel.GeodeImplementContext;
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.linq4j.tree.MethodCallExpression;
import org.apache.calcite.linq4j.tree.Types;
import org.apache.calcite.plan.ConventionTraitDef;
import org.apache.calcite.plan.RelOptCluster;
import org.apache.calcite.plan.RelOptCost;
import org.apache.calcite.plan.RelOptPlanner;
import org.apache.calcite.plan.RelTraitSet;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.convert.ConverterImpl;
import org.apache.calcite.rel.metadata.RelMetadataQuery;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.util.BuiltInMethod;
import org.apache.calcite.util.Pair;

import com.google.common.collect.Lists;

import java.lang.reflect.Method;
import java.util.AbstractList;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import static org.apache.calcite.adapter.geode.rel.GeodeRules.geodeFieldNames;

/**
 * Relational expression representing a scan of a table in a Geode data source.
 */
public class GeodeToEnumerableConverter extends ConverterImpl implements EnumerableRel {

  protected GeodeToEnumerableConverter(RelOptCluster cluster,
      RelTraitSet traitSet, RelNode input) {
    super(cluster, ConventionTraitDef.INSTANCE, traitSet, input);
  }

  @Override public RelNode copy(RelTraitSet traitSet, List inputs) {
    return new GeodeToEnumerableConverter(
        getCluster(), traitSet, sole(inputs));
  }

  @Override public RelOptCost computeSelfCost(RelOptPlanner planner,
      RelMetadataQuery mq) {
    return super.computeSelfCost(planner, mq).multiplyBy(.1);
  }

  /**
   * Reference to the method {@link GeodeTable.GeodeQueryable#query},
   * used in the {@link Expression}.
   */
  private static final Method GEODE_QUERY_METHOD =
      Types.lookupMethod(GeodeTable.GeodeQueryable.class, "query", List.class,
          List.class, List.class, List.class, List.class, List.class,
          Long.class);

  /**
   * {@inheritDoc}
   *
   * @param implementor GeodeImplementContext
   */
  @Override public Result implement(EnumerableRelImplementor implementor, Prefer pref) {

    // travers all relations form this to the scan leaf
    final GeodeImplementContext geodeImplementContext = new GeodeImplementContext();
    ((GeodeRel) getInput()).implement(geodeImplementContext);

    final RelDataType rowType = getRowType();

    // PhysType is Enumerable Adapter class that maps SQL types (getRowType)
    // with physical Java types (getJavaTypes())
    final PhysType physType = PhysTypeImpl.of(
        implementor.getTypeFactory(),
        rowType,
        pref.prefer(JavaRowFormat.ARRAY));

    final List physFieldClasses = new AbstractList() {
      public Class get(int index) {
        return physType.fieldClass(index);
      }

      public int size() {
        return rowType.getFieldCount();
      }
    };

    // Expression meta-program for calling the GeodeTable.GeodeQueryable#query
    // method form the generated code
    final BlockBuilder blockBuilder = new BlockBuilder().append(
        Expressions.call(
            geodeImplementContext.table.getExpression(GeodeTable.GeodeQueryable.class),
            GEODE_QUERY_METHOD,
            // fields
            constantArrayList(Pair.zip(geodeFieldNames(rowType), physFieldClasses), Pair.class),
            // selected fields
            constantArrayList(toListMapPairs(geodeImplementContext.selectFields), Pair.class),
            // aggregate functions
            constantArrayList(
                toListMapPairs(geodeImplementContext.oqlAggregateFunctions), Pair.class),
            constantArrayList(geodeImplementContext.groupByFields, String.class),
            constantArrayList(geodeImplementContext.whereClause, String.class),
            constantArrayList(geodeImplementContext.orderByFields, String.class),
            Expressions.constant(geodeImplementContext.limitValue)));

    return implementor.result(physType, blockBuilder.toBlock());
  }

  private static List> toListMapPairs(Map map) {
    List> selectList = new ArrayList<>();
    for (Map.Entry entry : Pair.zip(map.keySet(), map.values())) {
      selectList.add(entry);
    }
    return selectList;
  }

  /**
   * E.g. {@code constantArrayList("x", "y")} returns
   * "Arrays.asList('x', 'y')".
   */
  private static  MethodCallExpression constantArrayList(List values,
      Class clazz) {
    return Expressions.call(BuiltInMethod.ARRAYS_AS_LIST.method,
        Expressions.newArrayInit(clazz, constantList(values)));
  }

  /**
   * E.g. {@code constantList("x", "y")} returns
   * {@code {ConstantExpression("x"), ConstantExpression("y")}}.
   */
  private static  List constantList(List values) {
    return Lists.transform(values, Expressions::constant);
  }
}

// End GeodeToEnumerableConverter.java