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/*
 * Copyright (c) 2015. Qubole Inc
 * Licensed 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 com.qubole.quark.planner;

import org.apache.calcite.adapter.enumerable.EnumerableConvention;
import org.apache.calcite.adapter.enumerable.EnumerableRel;
import org.apache.calcite.adapter.enumerable.EnumerableRelImplementor;
import org.apache.calcite.adapter.enumerable.PhysType;
import org.apache.calcite.adapter.enumerable.PhysTypeImpl;
import org.apache.calcite.linq4j.tree.Blocks;
import org.apache.calcite.linq4j.tree.Expressions;
import org.apache.calcite.plan.RelOptCluster;
import org.apache.calcite.plan.RelOptPlanner;
import org.apache.calcite.plan.RelOptTable;
import org.apache.calcite.plan.RelTraitSet;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.RelWriter;
import org.apache.calcite.rel.core.TableScan;
import org.apache.calcite.rel.type.RelDataType;

import java.util.List;

/**
 * Relational expression representing a scan of a CSV file.
 * Like any table scan, it serves as a leaf node of a query tree.
 */
public class QuarkTableScan extends TableScan implements EnumerableRel {
  final QuarkTable quarkTable;

  protected QuarkTableScan(RelOptCluster cluster, RelOptTable table,
                           QuarkTable quarkTable) {
    super(cluster, cluster.traitSetOf(EnumerableConvention.INSTANCE), table);
    this.quarkTable = quarkTable;

    assert quarkTable != null;
  }

  @Override
  public RelNode copy(RelTraitSet traitSet, List inputs) {
    assert inputs.isEmpty();
    return new QuarkTableScan(getCluster(), table, quarkTable);
  }

  @Override
  public RelWriter explainTerms(RelWriter pw) {
    return super.explainTerms(pw)
        .item("fields", table.getRowType());
  }

  @Override
  public RelDataType deriveRowType() {
    return table.getRowType();
  }

  @Override
  public void register(RelOptPlanner planner) {
    planner.addRule(ProjectRule.INSTANCE);
  }

  public Result implement(EnumerableRelImplementor implementor, Prefer pref) {
    PhysType physType =
        PhysTypeImpl.of(
            implementor.getTypeFactory(),
            getRowType(),
            pref.preferArray());

    return implementor.result(
        physType,
        Blocks.toBlock(
            Expressions.call(table.getExpression(QuarkTable.class),
                "project",
                Expressions.constant(QuarkEnumerator.identityList(
                    getRowType().getFieldCount())))));
  }

  public QuarkTable getQuarkTable() {
    return quarkTable;
  }

  @Override public boolean equals(Object obj) {
    return obj == this
        || obj instanceof QuarkTableScan
        && quarkTable.equals(((QuarkTableScan) obj).getQuarkTable());
  }

  @Override public int hashCode() {
    return quarkTable.hashCode();
  }
}