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/*
 * Copyright 2017 HugeGraph Authors
 *
 * 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 com.baidu.hugegraph.traversal.optimize;

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

import org.apache.tinkerpop.gremlin.process.traversal.step.map.GraphStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.HasContainer;
import org.apache.tinkerpop.gremlin.structure.Element;
import org.apache.tinkerpop.gremlin.structure.util.StringFactory;
import org.apache.tinkerpop.gremlin.util.iterator.IteratorUtils;
import org.slf4j.Logger;

import com.baidu.hugegraph.HugeGraph;
import com.baidu.hugegraph.backend.query.ConditionQuery;
import com.baidu.hugegraph.backend.query.Query;
import com.baidu.hugegraph.backend.query.QueryResults;
import com.baidu.hugegraph.type.HugeType;
import com.baidu.hugegraph.util.Log;

public final class HugeGraphStep
             extends GraphStep implements QueryHolder {

    private static final long serialVersionUID = -679873894532085972L;

    private static final Logger LOG = Log.logger(HugeGraphStep.class);

    private final List hasContainers = new ArrayList<>();

    // Store limit/order-by
    private final Query queryInfo = new Query(HugeType.UNKNOWN);

    private Iterator lastTimeResults = QueryResults.emptyIterator();

    public HugeGraphStep(final GraphStep originGraphStep) {
        super(originGraphStep.getTraversal(),
              originGraphStep.getReturnClass(),
              originGraphStep.isStartStep(),
              originGraphStep.getIds());

        originGraphStep.getLabels().forEach(this::addLabel);

        boolean queryVertex = this.returnsVertex();
        boolean queryEdge = this.returnsEdge();
        assert queryVertex || queryEdge;
        this.setIteratorSupplier(() -> {
            Iterator results = queryVertex ? this.vertices() : this.edges();
            this.lastTimeResults = results;
            return results;
        });
    }

    protected long count() {
        if (this.returnsVertex()) {
            return this.verticesCount();
        } else {
            assert this.returnsEdge();
            return this.edgesCount();
        }
    }

    private long verticesCount() {
        if (!this.hasIds()) {
            HugeGraph graph = TraversalUtil.getGraph(this);
            Query query = this.makeQuery(graph, HugeType.VERTEX);
            return graph.queryNumber(query).longValue();
        }
        return IteratorUtils.count(this.vertices());
    }

    private long edgesCount() {
        if (!this.hasIds()) {
            HugeGraph graph = TraversalUtil.getGraph(this);
            Query query = this.makeQuery(graph, HugeType.EDGE);
            return graph.queryNumber(query).longValue();
        }
        return IteratorUtils.count(this.edges());
    }

    private Iterator vertices() {
        LOG.debug("HugeGraphStep.vertices(): {}", this);

        HugeGraph graph = TraversalUtil.getGraph(this);
        // g.V().hasId(EMPTY_LIST) will set ids to null
        if (this.ids == null) {
            return QueryResults.emptyIterator();
        }

        if (this.hasIds()) {
            return TraversalUtil.filterResult(this.hasContainers,
                                              graph.vertices(this.ids));
        }

        Query query = this.makeQuery(graph, HugeType.VERTEX);
        @SuppressWarnings("unchecked")
        Iterator result = (Iterator) graph.vertices(query);
        return result;
    }

    private Iterator edges() {
        LOG.debug("HugeGraphStep.edges(): {}", this);

        HugeGraph graph = TraversalUtil.getGraph(this);

        // g.E().hasId(EMPTY_LIST) will set ids to null
        if (this.ids == null) {
            return QueryResults.emptyIterator();
        }

        if (this.hasIds()) {
            return TraversalUtil.filterResult(this.hasContainers,
                                              graph.edges(this.ids));
        }

        Query query = this.makeQuery(graph, HugeType.EDGE);
        @SuppressWarnings("unchecked")
        Iterator result = (Iterator) graph.edges(query);
        return result;
    }

    private boolean hasIds() {
        return this.ids != null && this.ids.length > 0;
    }

    private Query makeQuery(HugeGraph graph, HugeType type) {
        Query query = null;
        if (this.hasContainers.isEmpty()) {
            // Query all
            query = new Query(type);
        } else {
            ConditionQuery q = new ConditionQuery(type);
            query = TraversalUtil.fillConditionQuery(q, this.hasContainers,
                                                     graph);
        }

        query = this.injectQueryInfo(query);
        return query;
    }

    @Override
    public String toString() {
        if (this.hasContainers.isEmpty()) {
            return super.toString();
        }

        return this.ids.length == 0 ?
               StringFactory.stepString(this,
                                        this.returnClass.getSimpleName(),
                                        this.hasContainers) :
               StringFactory.stepString(this,
                                        this.returnClass.getSimpleName(),
                                        Arrays.toString(this.ids),
                                        this.hasContainers);
    }

    @Override
    public List getHasContainers() {
        return Collections.unmodifiableList(this.hasContainers);
    }

    @Override
    public void addHasContainer(final HasContainer has) {
        if (SYSPROP_PAGE.equals(has.getKey())) {
            this.setPage((String) has.getValue());
            return;
        }
        this.hasContainers.add(has);
    }

    @Override
    public Query queryInfo() {
        return this.queryInfo;
    }

    @Override
    public Iterator lastTimeResults() {
        return this.lastTimeResults;
    }

    @Override
    public int hashCode() {
        return super.hashCode() ^
               this.queryInfo.hashCode() ^
               this.hasContainers.hashCode();
    }
}