/*

 * Copyright (c) 1998, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.awt.geom;

final class ChainEnd {

    CurveLink head;

    CurveLink tail;

    ChainEnd partner;

    int etag;

    public ChainEnd(CurveLink first, ChainEnd partner) {

        this.head = first;

        this.tail = first;

        this.partner = partner;

        this.etag = first.getEdgeTag();

    }

    public CurveLink getChain() {

        return head;

    }

    public void setOtherEnd(ChainEnd partner) {

        this.partner = partner;

    }

    public ChainEnd getPartner() {

        return partner;

    }

    /*

     * Returns head of a complete chain to be added to subcurves

     * or null if the links did not complete such a chain.

     */

    public CurveLink linkTo(ChainEnd that) {

        if (etag == AreaOp.ETAG_IGNORE ||

            that.etag == AreaOp.ETAG_IGNORE)

        {

            throw new InternalError("ChainEnd linked more than once!");

        }

        if (etag == that.etag) {

            throw new InternalError("Linking chains of the same type!");

        }

        ChainEnd enter, exit;

        // assert(partner.etag != that.partner.etag);

        if (etag == AreaOp.ETAG_ENTER) {

            enter = this;

            exit = that;

        } else {

            enter = that;

            exit = this;

        }

        // Now make sure these ChainEnds are not linked to any others...

        etag = AreaOp.ETAG_IGNORE;

        that.etag = AreaOp.ETAG_IGNORE;

        // Now link everything up...

        enter.tail.setNext(exit.head);

        enter.tail = exit.tail;

        if (partner == that) {

            // Curve has closed on itself...

            return enter.head;

        }

        // Link this chain into one end of the chain formed by the partners

        ChainEnd otherenter = exit.partner;

        ChainEnd otherexit = enter.partner;

        otherenter.partner = otherexit;

        otherexit.partner = otherenter;

        if (enter.head.getYTop() < otherenter.head.getYTop()) {

            enter.tail.setNext(otherenter.head);

            otherenter.head = enter.head;

        } else {

            otherexit.tail.setNext(enter.head);

            otherexit.tail = enter.tail;

        }

        return null;

    }

    public void addLink(CurveLink newlink) {

        if (etag == AreaOp.ETAG_ENTER) {

            tail.setNext(newlink);

            tail = newlink;

        } else {

            newlink.setNext(head);

            head = newlink;

        }

    }

    public double getX() {

        if (etag == AreaOp.ETAG_ENTER) {

            return tail.getXBot();

        } else {

            return head.getXBot();

        }

    }

}