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/*
 * Copyright © 2021-present Arcade Data Ltd ([email protected])
 *
 * 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.
 *
 * SPDX-FileCopyrightText: 2021-present Arcade Data Ltd ([email protected])
 * SPDX-License-Identifier: Apache-2.0
 */
package com.arcadedb.query.sql.executor;

import com.arcadedb.exception.TimeoutException;
import com.arcadedb.query.sql.parser.FieldMatchPathItem;
import com.arcadedb.query.sql.parser.MultiMatchPathItem;

import java.util.*;

/**
 * @author Luigi Dell'Aquila
 */
public class MatchStep extends AbstractExecutionStep {
  protected final EdgeTraversal      edge;
  private         ResultSet          upstream;
  private         Result             lastUpstreamRecord;
  private         MatchEdgeTraverser traverser;
  private         Result             nextResult;

  public MatchStep(final CommandContext context, final EdgeTraversal edge, final boolean profilingEnabled) {
    super(context, profilingEnabled);
    this.edge = edge;
  }

  @Override
  public void reset() {
    this.upstream = null;
    this.lastUpstreamRecord = null;
    this.traverser = null;
    this.nextResult = null;
  }

  @Override
  public ResultSet syncPull(final CommandContext context, final int nRecords) throws TimeoutException {
    return new ResultSet() {
      int localCount = 0;

      @Override
      public boolean hasNext() {
        if (localCount >= nRecords) {
          return false;
        }
        if (nextResult == null) {
          fetchNext(context, nRecords);
        }
        return nextResult != null;
      }

      @Override
      public Result next() {
        if (localCount >= nRecords) {
          throw new NoSuchElementException();
        }
        if (nextResult == null) {
          fetchNext(context, nRecords);
        }
        if (nextResult == null) {
          throw new NoSuchElementException();
        }
        final Result result = nextResult;
        fetchNext(context, nRecords);
        localCount++;
        context.setVariable("matched", result);
        return result;
      }

    };
  }

  private void fetchNext(final CommandContext context, final int nRecords) {
    nextResult = null;
    while (true) {
      if (traverser != null && traverser.hasNext(context)) {
        nextResult = traverser.next(context);
        break;
      }

      if (upstream == null || !upstream.hasNext()) {
        upstream = getPrev().syncPull(context, nRecords);
      }
      if (!upstream.hasNext()) {
        return;
      }

      lastUpstreamRecord = upstream.next();

      traverser = createTraverser(lastUpstreamRecord);

      boolean found = false;
      while (traverser.hasNext(context)) {
        nextResult = traverser.next(context);
        if (nextResult != null) {
          found = true;
          break;
        }
      }
      if (found) {
        break;
      }
    }
  }

  protected MatchEdgeTraverser createTraverser(final Result lastUpstreamRecord) {
    if (edge.edge.item instanceof MultiMatchPathItem) {
      return new MatchMultiEdgeTraverser(lastUpstreamRecord, edge);
    } else if (edge.edge.item instanceof FieldMatchPathItem) {
      return new MatchFieldTraverser(lastUpstreamRecord, edge);
    } else if (edge.out) {
      return new MatchEdgeTraverser(lastUpstreamRecord, edge);
    } else {
      return new MatchReverseEdgeTraverser(lastUpstreamRecord, edge);
    }
  }

  @Override
  public String prettyPrint(final int depth, final int indent) {
    final String spaces = ExecutionStepInternal.getIndent(depth, indent);
    final StringBuilder result = new StringBuilder();
    result.append(spaces);
    result.append("+ MATCH ");
    if (edge.out) {
      result.append("     ---->\n");
    } else {
      result.append("     <----\n");
    }
    result.append(spaces);
    result.append("  ");
    result.append("{").append(edge.edge.out.alias).append("}");
    result.append(edge.edge.item.getMethod());
    result.append("{").append(edge.edge.in.alias).append("}");
    return result.toString();
  }
}