/*
 * 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.drill.exec.planner.physical;

import org.apache.drill.common.expression.IfExpression;
import org.apache.drill.common.expression.NullExpression;
import com.google.common.collect.Lists;
import org.apache.calcite.linq4j.Ord;
import org.apache.calcite.util.BitSets;
import org.apache.calcite.util.ImmutableBitSet;
import org.apache.drill.common.expression.ExpressionPosition;
import org.apache.drill.common.expression.FieldReference;
import org.apache.drill.common.expression.FunctionCall;
import org.apache.drill.common.expression.LogicalExpression;
import org.apache.drill.common.expression.ValueExpressions;
import org.apache.drill.common.logical.data.NamedExpression;
import org.apache.drill.exec.planner.common.DrillAggregateRelBase;
import org.apache.drill.exec.planner.physical.visitor.PrelVisitor;
import org.apache.calcite.rel.core.AggregateCall;
import org.apache.calcite.rel.InvalidRelException;
import org.apache.calcite.rel.RelCollations;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.plan.RelOptCluster;
import org.apache.calcite.plan.RelTraitSet;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.sql.SqlAggFunction;
import org.apache.calcite.sql.SqlFunctionCategory;
import org.apache.calcite.sql.SqlKind;
import org.apache.calcite.sql.type.OperandTypes;
import org.apache.calcite.sql.type.ReturnTypes;
import org.apache.calcite.util.Optionality;

import java.util.Collections;
import java.util.Iterator;
import java.util.List;

public abstract class AggPrelBase extends DrillAggregateRelBase implements Prel {

  public enum OperatorPhase {

    // Single phase aggregate
    PHASE_1of1("Single"),

    // Distributed aggregate: partitioned first phase
    PHASE_1of2("1st"),

    // Distibuted aggregate: non-partitioned overall aggregation
    // phase
    PHASE_2of2("2nd");

    private final String name;

    OperatorPhase(String name) {
      this.name = name;
    }

    public boolean hasTwo() {
      return this != PHASE_1of1;
    }

    public boolean is1st() {
      return this == PHASE_1of2;
    }

    public boolean is2nd() {
      return this == PHASE_2of2;
    }

    public boolean isFinal() {
      return this != PHASE_1of2;
    }

    public String getName() {
      return name;
    }
  }

  protected OperatorPhase operPhase = OperatorPhase.PHASE_1of1; // default phase
  protected List<NamedExpression> keys = Lists.newArrayList();
  protected List<NamedExpression> aggExprs = Lists.newArrayList();
  protected List<AggregateCall> phase2AggCallList = Lists.newArrayList();

  /**
   * Specialized aggregate function for SUMing the COUNTs.  Since return type of
   * COUNT is non-nullable and return type of SUM is nullable, this class enables
   * creating a SUM whose return type is non-nullable.
   *
   */
  public static class SqlSumCountAggFunction extends SqlAggFunction {

    private final RelDataType type;

    public SqlSumCountAggFunction(RelDataType type) {
      super("$SUM0",
          null,
          SqlKind.OTHER_FUNCTION,
          ReturnTypes.BIGINT, // use the inferred return type of SqlCountAggFunction
          null,
          OperandTypes.NUMERIC,
          SqlFunctionCategory.NUMERIC,
          false,
          false,
          Optionality.FORBIDDEN);

      this.type = type;
    }

    public RelDataType getType() {
      return type;
    }
  }

  public AggPrelBase(RelOptCluster cluster,
                     RelTraitSet traits,
                     RelNode child,
                     ImmutableBitSet groupSet,
                     List<ImmutableBitSet> groupSets,
                     List<AggregateCall> aggCalls,
                     OperatorPhase phase) throws InvalidRelException {
    super(cluster, traits, child, groupSet, groupSets, aggCalls);
    this.operPhase = phase;
    createKeysAndExprs();
  }

  public OperatorPhase getOperatorPhase() {
    return operPhase;
  }

  public List<NamedExpression> getKeys() {
    return keys;
  }

  public List<NamedExpression> getAggExprs() {
    return aggExprs;
  }

  public List<AggregateCall> getPhase2AggCalls() {
    return phase2AggCallList;
  }

  protected void createKeysAndExprs() {
    final List<String> childFields = getInput().getRowType().getFieldNames();
    final List<String> fields = getRowType().getFieldNames();

    for (int group : BitSets.toIter(groupSet)) {
      FieldReference fr = FieldReference.getWithQuotedRef(childFields.get(group));
      keys.add(new NamedExpression(fr, fr));
    }

    for (Ord<AggregateCall> aggCall : Ord.zip(aggCalls)) {
      int aggExprOrdinal = groupSet.cardinality() + aggCall.i;
      FieldReference ref = FieldReference.getWithQuotedRef(fields.get(aggExprOrdinal));
      LogicalExpression expr = toDrill(aggCall.e, childFields);
      NamedExpression ne = new NamedExpression(expr, ref);
      aggExprs.add(ne);

      if (getOperatorPhase() == OperatorPhase.PHASE_1of2) {
        if (aggCall.e.getAggregation().getName().equals("COUNT")) {
          // If we are doing a COUNT aggregate in Phase1of2, then in Phase2of2 we should SUM the COUNTs,
          SqlAggFunction sumAggFun = new SqlSumCountAggFunction(aggCall.e.getType());
          AggregateCall newAggCall =
              AggregateCall.create(
                  sumAggFun,
                  aggCall.e.isDistinct(),
                  aggCall.e.isApproximate(),
                  false,
                  Collections.singletonList(aggExprOrdinal),
                  aggCall.e.filterArg,
                  null,
                  RelCollations.EMPTY,
                  aggCall.e.getType(),
                  aggCall.e.getName());

          phase2AggCallList.add(newAggCall);
        } else {
          AggregateCall newAggCall =
              AggregateCall.create(
                  aggCall.e.getAggregation(),
                  aggCall.e.isDistinct(),
                  aggCall.e.isApproximate(),
                  false,
                  Collections.singletonList(aggExprOrdinal),
                  aggCall.e.filterArg,
                  null,
                  RelCollations.EMPTY,
                  aggCall.e.getType(),
                  aggCall.e.getName());

          phase2AggCallList.add(newAggCall);
        }
      }
    }
  }

  protected LogicalExpression toDrill(AggregateCall call, List<String> fn) {
    List<LogicalExpression> args = Lists.newArrayList();
    for (Integer i : call.getArgList()) {
      LogicalExpression expr = FieldReference.getWithQuotedRef(fn.get(i));
      expr = getArgumentExpression(call, fn, expr);
      args.add(expr);
    }

    if (SqlKind.COUNT.name().equals(call.getAggregation().getName()) && args.isEmpty()) {
      LogicalExpression expr = new ValueExpressions.LongExpression(1L);
      expr = getArgumentExpression(call, fn, expr);
      args.add(expr);
    }
    return new FunctionCall(call.getAggregation().getName().toLowerCase(), args, ExpressionPosition.UNKNOWN);
  }

  private static LogicalExpression getArgumentExpression(AggregateCall call, List<String> fn,
      LogicalExpression expr) {
    if (call.hasFilter()) {
      return IfExpression.newBuilder()
          .setIfCondition(new IfExpression.IfCondition(FieldReference.getWithQuotedRef(fn.get(call.filterArg)), expr))
          .setElse(NullExpression.INSTANCE)
          .build();
    }
    return expr;
  }

  @Override
  public Iterator<Prel> iterator() {
    return PrelUtil.iter(getInput());
  }

  @Override
  public <T, X, E extends Throwable> T accept(PrelVisitor<T, X, E> logicalVisitor, X value) throws E {
    return logicalVisitor.visitPrel(this, value);
  }

  @Override
  public boolean needsFinalColumnReordering() {
    return true;
  }

  @Override
  public Prel prepareForLateralUnnestPipeline(List<RelNode> children) {
    List<Integer> groupingCols = Lists.newArrayList();
    groupingCols.add(0);
    for (int groupingCol : groupSet.asList()) {
      groupingCols.add(groupingCol + 1);
    }

    ImmutableBitSet groupingSet = ImmutableBitSet.of(groupingCols);
    List<ImmutableBitSet> groupingSets = Lists.newArrayList();
    groupingSets.add(groupingSet);
    List<AggregateCall> aggregateCalls = Lists.newArrayList();
    for (AggregateCall aggCall : aggCalls) {
      List<Integer> arglist = Lists.newArrayList();
      for (int arg : aggCall.getArgList()) {
        arglist.add(arg + 1);
      }
      aggregateCalls.add(AggregateCall.create(aggCall.getAggregation(),
          aggCall.isDistinct(),
          aggCall.isApproximate(),
          false,
          arglist,
          aggCall.filterArg,
          null,
          RelCollations.EMPTY,
          aggCall.type,
          aggCall.name));
    }
    return (Prel) copy(traitSet, children.get(0), groupingSet, groupingSets, aggregateCalls);
  }
}