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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.solr.handler.sql;

import java.util.AbstractList;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
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.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.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.runtime.Hook;
import org.apache.calcite.util.BuiltInMethod;
import org.apache.calcite.util.Pair;

/** Relational expression representing a scan of a table in Solr */
class SolrToEnumerableConverter extends ConverterImpl implements EnumerableRel {
  SolrToEnumerableConverter(RelOptCluster cluster, RelTraitSet traits, RelNode input) {
    super(cluster, ConventionTraitDef.INSTANCE, traits, input);
  }

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

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

  @Override
  public Result implement(EnumerableRelImplementor implementor, Prefer pref) {
    // Generates a call to "query" with the appropriate fields
    final BlockBuilder list = new BlockBuilder();
    final SolrRel.Implementor solrImplementor = new SolrRel.Implementor();
    solrImplementor.visitChild(0, getInput());
    final RelDataType rowType = getRowType();
    final PhysType physType =
        PhysTypeImpl.of(implementor.getTypeFactory(), rowType, pref.prefer(JavaRowFormat.ARRAY));
    final Expression table =
        list.append("table", solrImplementor.table.getExpression(SolrTable.SolrQueryable.class));
    final Expression fields =
        list.append(
            "fields",
            constantArrayList(
                Pair.zip(
                    generateFields(
                        SolrRules.solrFieldNames(rowType), solrImplementor.fieldMappings),
                    new AbstractList>() {
                      @Override
                      public Class get(int index) {
                        return physType.fieldClass(index);
                      }

                      @Override
                      public int size() {
                        return rowType.getFieldCount();
                      }
                    }),
                Pair.class));
    final Expression query =
        list.append("query", Expressions.constant(solrImplementor.query, String.class));
    final Expression orders =
        list.append("orders", constantArrayList(solrImplementor.orders, Pair.class));
    final Expression buckets =
        list.append("buckets", constantArrayList(solrImplementor.buckets, String.class));
    final Expression metricPairs =
        list.append("metricPairs", constantArrayList(solrImplementor.metricPairs, Pair.class));
    final Expression limit = list.append("limit", Expressions.constant(solrImplementor.limitValue));
    final Expression negativeQuery =
        list.append(
            "negativeQuery",
            Expressions.constant(Boolean.toString(solrImplementor.negativeQuery), String.class));
    final Expression havingPredicate =
        list.append(
            "havingTest", Expressions.constant(solrImplementor.havingPredicate, String.class));
    final Expression offset =
        list.append("offset", Expressions.constant(solrImplementor.offsetValue));
    Expression enumerable =
        list.append(
            "enumerable",
            Expressions.call(
                table,
                SolrMethod.SOLR_QUERYABLE_QUERY.method,
                fields,
                query,
                orders,
                buckets,
                metricPairs,
                limit,
                negativeQuery,
                havingPredicate,
                offset));
    Hook.QUERY_PLAN.run(query);
    list.add(Expressions.return_(null, enumerable));
    return implementor.result(physType, list.toBlock());
  }

  private List generateFields(List queryFields, Map fieldMappings) {

    if (fieldMappings.isEmpty()) {
      return queryFields;
    } else {
      List fields = new ArrayList<>();
      for (String field : queryFields) {
        fields.add(getField(fieldMappings, field));
      }
      return fields;
    }
  }

  private String getField(Map fieldMappings, String field) {
    String retField = field;
    while (fieldMappings.containsKey(field)) {
      field = fieldMappings.getOrDefault(field, retField);
      if (retField.equals(field)) {
        break;
      } else {
        retField = field;
      }
    }
    return retField;
  }

  /** 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 "{ConstantExpression("x"),
   * ConstantExpression("y")}".
   */
  private static  List constantList(List values) {
    return values.stream().map(Expressions::constant).collect(Collectors.toUnmodifiableList());
  }
}