/*
 * 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
 *
 *   https://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-License-Identifier: Apache-2.0
 */

package org.apache.jena.sparql.syntax;

import java.util.ArrayList;
import java.util.List;

import org.apache.jena.graph.Triple;
import org.apache.jena.sparql.util.NodeIsomorphismMap;

/** A number of graph query elements.
 *  Evaluation is a conjunction(AND) of the elements of the groups */

public class ElementGroup extends Element {
    List<Element> elements = new ArrayList<>();

    public ElementGroup() {}

    public void addElement(Element el) {
        elements.add(el);
    }

    // In SPARQL, triple patterns are in basic graph patterns.
    // This is a helper method.

    public void addTriplePattern(Triple t) {
        ensureBGP().addTriple(t);
    }

    // Ensure the current top element is a basic graph pattern.
    private ElementTriplesBlock ensureBGP() {
        if ( elements.size() == 0 )
            return pushBGP();

        Element top = top();
        ElementTriplesBlock bgp = null;
        if ( top instanceof ElementTriplesBlock )
            return (ElementTriplesBlock)top;
        return pushBGP();
    }

    private ElementTriplesBlock pushBGP() {
        ElementTriplesBlock bgp = new ElementTriplesBlock();
        elements.add(bgp);
        return bgp;
    }

    private void setTop(Element el) { elements.set(elements.size()-1, el); }
    private Element top() { return elements.get(elements.size()-1); }

    public int mark() { return elements.size(); }

    public List<Element> getElements()  { return elements; }
    public boolean isEmpty()            { return elements.size() == 0; }
    public int size()                   { return elements.size(); }
    public Element get(int idx)         { return elements.get(idx); }
    public Element getLast() {
        if ( elements.isEmpty() )
            return null;
        return elements.get(elements.size()-1);
    }

    @Override
    public int hashCode()
    {
        int calcHashCode = Element.HashGroup; // So the empty group isn't zero.
        calcHashCode ^=  getElements().hashCode();
        return calcHashCode;
    }

    @Override
    public boolean equalTo(Element el2, NodeIsomorphismMap isoMap)
    {
        if ( el2 == null ) return false;

        if ( ! ( el2 instanceof ElementGroup) )
            return false;
        ElementGroup eg2 = (ElementGroup)el2;
        if ( this.getElements().size() != eg2.getElements().size() )
            return false;
        for ( int i = 0; i < this.getElements().size(); i++ )
        {
            Element e1 = getElements().get(i);
            Element e2 = eg2.getElements().get(i);
            if ( ! e1.equalTo(e2, isoMap) )
                return false;
        }
        return true;
    }

    @Override
    public void visit(ElementVisitor v) { v.visit(this); }
}
