/*
 * 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.tinkerpop.gremlin.process.traversal.step.map;

import org.apache.tinkerpop.gremlin.process.traversal.Step;
import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
import org.apache.tinkerpop.gremlin.process.traversal.Traverser;
import org.apache.tinkerpop.gremlin.process.traversal.TraverserGenerator;
import org.apache.tinkerpop.gremlin.process.traversal.step.Mutating;
import org.apache.tinkerpop.gremlin.process.traversal.step.Scoping;
import org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.Parameters;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.event.CallbackRegistry;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.event.Event;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.event.ListCallbackRegistry;
import org.apache.tinkerpop.gremlin.process.traversal.strategy.decoration.EventStrategy;
import org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement;
import org.apache.tinkerpop.gremlin.process.traversal.util.FastNoSuchElementException;
import org.apache.tinkerpop.gremlin.structure.T;
import org.apache.tinkerpop.gremlin.structure.Vertex;
import org.apache.tinkerpop.gremlin.structure.util.StringFactory;

import java.util.List;
import java.util.Set;

/**
 * @author Marko A. Rodriguez (http://markorodriguez.com)
 * @author Stephen Mallette (http://stephen.genoprime.com)
 */
public class AddVertexStartStep extends AbstractStep<Vertex, Vertex>
        implements Mutating<Event.VertexAddedEvent>, TraversalParent, Scoping {

    private Parameters parameters = new Parameters();
    private boolean first = true;
    private CallbackRegistry<Event.VertexAddedEvent> callbackRegistry;

    public AddVertexStartStep(final Traversal.Admin traversal, final String label) {
        super(traversal);
        this.parameters.set(this, T.label, label);
    }

    public AddVertexStartStep(final Traversal.Admin traversal, final Traversal<?, String> vertexLabelTraversal) {
        super(traversal);
        this.parameters.set(this, T.label, vertexLabelTraversal);
    }

    @Override
    public Parameters getParameters() {
        return this.parameters;
    }

    @Override
    public Set<String> getScopeKeys() {
        return this.parameters.getReferencedLabels();
    }

    @Override
    public <S, E> List<Traversal.Admin<S, E>> getLocalChildren() {
        return this.parameters.getTraversals();
    }

    @Override
    public void configure(final Object... keyValues) {
        this.parameters.set(this, keyValues);
    }

    @Override
    protected Traverser.Admin<Vertex> processNextStart() {
        if (this.first) {
            this.first = false;
            final TraverserGenerator generator = this.getTraversal().getTraverserGenerator();
            final Vertex vertex = this.getTraversal().getGraph().get().addVertex(this.parameters.getKeyValues(generator.generate(false, (Step) this, 1L)));
            if (this.callbackRegistry != null) {
                final EventStrategy eventStrategy = getTraversal().getStrategies().getStrategy(EventStrategy.class).get();
                final Event.VertexAddedEvent vae = new Event.VertexAddedEvent(eventStrategy.detach(vertex));
                this.callbackRegistry.getCallbacks().forEach(c -> c.accept(vae));
            }
            return generator.generate(vertex, this, 1L);
        } else
            throw FastNoSuchElementException.instance();
    }

    @Override
    public CallbackRegistry<Event.VertexAddedEvent> getMutatingCallbackRegistry() {
        if (null == this.callbackRegistry) this.callbackRegistry = new ListCallbackRegistry<>();
        return this.callbackRegistry;
    }

    @Override
    public Set<TraverserRequirement> getRequirements() {
        return this.getSelfAndChildRequirements();
    }

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

    @Override
    public void reset() {
        super.reset();
    }

    @Override
    public String toString() {
        return StringFactory.stepString(this, this.parameters);
    }

    @Override
    public void setTraversal(final Traversal.Admin<?, ?> parentTraversal) {
        super.setTraversal(parentTraversal);
        this.parameters.getTraversals().forEach(this::integrateChild);
    }

    @Override
    public AddVertexStartStep clone() {
        final AddVertexStartStep clone = (AddVertexStartStep) super.clone();
        clone.parameters = this.parameters.clone();
        return clone;
    }
}