/*
 * 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.tajo.plan.rewrite;

import com.google.common.base.Optional;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.tajo.OverridableConf;
import org.apache.tajo.SessionVars;
import org.apache.tajo.catalog.TableDesc;
import org.apache.tajo.catalog.statistics.TableStats;
import org.apache.tajo.exception.TajoException;
import org.apache.tajo.exception.UnsupportedException;
import org.apache.tajo.plan.LogicalPlan;
import org.apache.tajo.plan.StorageService;
import org.apache.tajo.plan.expr.EvalNode;
import org.apache.tajo.plan.logical.LogicalNode;
import org.apache.tajo.plan.logical.ScanNode;
import org.apache.tajo.plan.visitor.BasicLogicalPlanVisitor;

import java.util.Stack;

public class TableStatUpdateRewriter implements LogicalPlanRewriteRule {
  private static final Log LOG = LogFactory.getLog(TableStatUpdateRewriter.class);

  private static final String NAME = "Table Stat Updater";

  @Override
  public String getName() {
    return NAME;
  }

  @Override
  public boolean isEligible(LogicalPlanRewriteRuleContext context) {
    return true;
  }

  @Override
  public LogicalPlan rewrite(LogicalPlanRewriteRuleContext context) throws TajoException {
    LogicalPlan plan = context.getPlan();
    LogicalPlan.QueryBlock rootBlock = plan.getRootBlock();

    Rewriter r = new Rewriter(context.getQueryContext(), context.getStorage());
    r.visit(rootBlock, plan, rootBlock, rootBlock.getRoot(), new Stack<LogicalNode>());
    return plan;
  }

  private final class Rewriter extends BasicLogicalPlanVisitor<Object, Object> {
    private final OverridableConf conf;
    private final StorageService storage;


    private Rewriter(OverridableConf conf, StorageService storage) {
      this.conf = conf;
      this.storage = storage;
    }

    @Override
    public Object visitScan(Object object, LogicalPlan plan, LogicalPlan.QueryBlock block, ScanNode scanNode,
                            Stack<LogicalNode> stack) throws TajoException {
      final TableDesc table = scanNode.getTableDesc();

      if (!isVirtual(table)) {
        final TableStats stats = getTableStat(table);
        final long tableSize = stats.getNumBytes();
        final Optional<EvalNode> filter = scanNode.hasQual() ? Optional.of(scanNode.getQual()) : Optional.<EvalNode>absent();

        // If USE_TABLE_VOLUME is set, we will update the table volume through a storage handler.
        // In addition, if the table size is zero, we will update too.
        // It is a good workaround to avoid suboptimal join orders without cheap cost.
        if (conf.getBool(SessionVars.USE_TABLE_VOLUME) || tableSize == 0) {
          table.getStats().setNumBytes(getTableVolume(table, filter));
        }
      }

      return scanNode;
    }

    private TableStats getTableStat(TableDesc table) {
      TableStats stats;
      if (table.getStats() == null) {
        stats = new TableStats();
        table.setStats(stats);
      } else {
        stats = table.getStats();
      }
      return stats;
    }

    private boolean isVirtual(TableDesc table) {
      return table.getMeta().getDataFormat().equals("SYSTEM");
    }

    private long getTableVolume(TableDesc table, Optional<EvalNode> filter) {
      try {
        if (table.getStats() != null) {
          return storage.getTableVolumn(table.getUri(), filter);
        }
      } catch (UnsupportedException t) {
        LOG.warn(table.getName() + " does not support Tablespace::getTableVolume()");
      }

      // By default, return -1;
      return -1;
    }
  }
}