/*
 * 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.
 */

/* $Id: ElementListUtils.java 1632007 2014-10-15 13:15:06Z lbernardo $ */

package org.apache.fop.layoutmgr;

import java.util.List;
import java.util.ListIterator;

import org.apache.fop.traits.MinOptMax;
import org.apache.fop.util.ListUtil;

Utilities for Knuth element lists.
/**
 * Utilities for Knuth element lists.
 */
public final class ElementListUtils {

    private ElementListUtils() {
        // Utility class.
    }

    
Removes legal breaks in an element list. A constraint can be specified to limit the
range in which the breaks are removed. Legal breaks occuring before at least
constraint.opt space is filled will be removed.
Params:
elements – the element list
constraint – min/opt/max value to restrict the range in which the breaks are removed.
Returns:
true if the opt constraint is bigger than the list contents/**
     * Removes legal breaks in an element list. A constraint can be specified to limit the
     * range in which the breaks are removed. Legal breaks occuring before at least
     * constraint.opt space is filled will be removed.
     * @param elements the element list
     * @param constraint min/opt/max value to restrict the range in which the breaks are removed.
     * @return true if the opt constraint is bigger than the list contents
     */
    public static boolean removeLegalBreaks(List elements, MinOptMax constraint) {
        return removeLegalBreaks(elements, constraint.getOpt());
    }

    
Removes legal breaks in an element list. A constraint can be specified to limit the
range in which the breaks are removed. Legal breaks occuring before at least
constraint space is filled will be removed.
Params:
elements – the element list
constraint – value to restrict the range in which the breaks are removed.
Returns:
true if the constraint is bigger than the list contents/**
     * Removes legal breaks in an element list. A constraint can be specified to limit the
     * range in which the breaks are removed. Legal breaks occuring before at least
     * constraint space is filled will be removed.
     * @param elements the element list
     * @param constraint value to restrict the range in which the breaks are removed.
     * @return true if the constraint is bigger than the list contents
     */
    public static boolean removeLegalBreaks(List elements, int constraint) {
        return removeLegalBreaks(elements, constraint, false);
    }

    
Removes legal breaks in an element list. A constraint can be specified to limit the
range in which the breaks are removed. Legal breaks within the space specified through the
constraint (starting from the end of the element list) will be removed.
Params:
elements – the element list
constraint – value to restrict the range in which the breaks are removed.
Returns:
true if the constraint is bigger than the list contents/**
     * Removes legal breaks in an element list. A constraint can be specified to limit the
     * range in which the breaks are removed. Legal breaks within the space specified through the
     * constraint (starting from the end of the element list) will be removed.
     * @param elements the element list
     * @param constraint value to restrict the range in which the breaks are removed.
     * @return true if the constraint is bigger than the list contents
     */
    public static boolean removeLegalBreaksFromEnd(List elements, int constraint) {
        return removeLegalBreaks(elements, constraint, true);
    }

    private static boolean removeLegalBreaks(List elements, int constraint, boolean fromEnd) {

        int len = 0;
        ListElement el;

        for (ListIterator iter = elements.listIterator(fromEnd ? elements.size() : 0);
                (fromEnd ? iter.hasPrevious() : iter.hasNext());) {

            if (fromEnd) {
                el = (ListElement) iter.previous();
            } else {
                el = (ListElement) iter.next();
            }

            if (el.isPenalty()) {
                KnuthPenalty penalty = (KnuthPenalty)el;
                //Convert penalty to break inhibitor
                if (penalty.getPenalty() < KnuthPenalty.INFINITE) {
                    iter.set(new KnuthPenalty(penalty.getWidth(), KnuthPenalty.INFINITE,
                            penalty.isPenaltyFlagged(), penalty.getPosition(),
                            penalty.isAuxiliary()));
                }
            } else if (el.isGlue()) {
                KnuthGlue glue = (KnuthGlue)el;
                len += glue.getWidth();
                //check if previous is a box
                if (!fromEnd) {
                    iter.previous();
                }
                el = (ListElement)iter.previous();
                iter.next();
                if (el.isBox()) {
                    //add break inhibitor
                    iter.add(new KnuthPenalty(0, KnuthPenalty.INFINITE, false,
                            null, false));
                }
                if (!fromEnd) {
                    iter.next();
                }
            } else if (el.isUnresolvedElement()) {
                if (el instanceof BreakElement) {
                    BreakElement breakEl = (BreakElement)el;
                    if (breakEl.getPenaltyValue() < KnuthPenalty.INFINITE) {
                        breakEl.setPenaltyValue(KnuthPenalty.INFINITE);
                    }
                } else if (el instanceof UnresolvedListElementWithLength) {
                    UnresolvedListElementWithLength uel = (UnresolvedListElementWithLength)el;
                    len += uel.getLength().getOpt();
                }
            } else {
                KnuthElement kel = (KnuthElement)el;
                len += kel.getWidth();
            }

            if (len >= constraint) {
                return false;
            }
        }

        return true;
    }

    
Calculates the content length of the given element list. Warning: It doesn't take any
stretch and shrink possibilities into account.
Params:
elems – the element list
start – element at which to start
end – element at which to stop
Returns:
the content length/**
     * Calculates the content length of the given element list. Warning: It doesn't take any
     * stretch and shrink possibilities into account.
     * @param elems the element list
     * @param start element at which to start
     * @param end element at which to stop
     * @return the content length
     */
    public static int calcContentLength(List elems, int start, int end) {
        ListIterator iter = elems.listIterator(start);
        int count = end - start + 1;
        int len = 0;
        while (iter.hasNext()) {
            ListElement el = (ListElement)iter.next();
            if (el.isBox()) {
                len += ((KnuthElement)el).getWidth();
            } else if (el.isGlue()) {
                len += ((KnuthElement)el).getWidth();
            } else {
                //log.debug("Ignoring penalty: " + el);
                //ignore penalties
            }
            count--;
            if (count == 0) {
                break;
            }
        }
        return len;
    }

    
Calculates the content length of the given element list. Warning: It doesn't take any
stretch and shrink possibilities into account.
Params:
elems – the element list
Returns:
the content length/**
     * Calculates the content length of the given element list. Warning: It doesn't take any
     * stretch and shrink possibilities into account.
     * @param elems the element list
     * @return the content length
     */
    public static int calcContentLength(List elems) {
        return calcContentLength(elems, 0, elems.size() - 1);
    }

    
Indicates whether the given element list ends with a forced break.
Params:
elems – the element list
Returns:
true if the list ends with a forced break/**
     * Indicates whether the given element list ends with a forced break.
     * @param elems the element list
     * @return true if the list ends with a forced break
     */
    public static boolean endsWithForcedBreak(List elems) {
        return ((ListElement) ListUtil.getLast(elems)).isForcedBreak();
    }

    
Indicates whether the given element list starts with a forced break.
Params:
elems – the element list
Returns:
true if the list starts with a forced break/**
     * Indicates whether the given element list starts with a forced break.
     * @param elems the element list
     * @return true if the list starts with a forced break
     */
    public static boolean startsWithForcedBreak(List elems) {
        return !elems.isEmpty() && ((ListElement) elems.get(0)).isForcedBreak();
    }

    
Indicates whether the given element list ends with a penalty with a non-infinite penalty
value.
Params:
elems – the element list
Returns:
true if the list ends with a non-infinite penalty/**
     * Indicates whether the given element list ends with a penalty with a non-infinite penalty
     * value.
     * @param elems the element list
     * @return true if the list ends with a non-infinite penalty
     */
    public static boolean endsWithNonInfinitePenalty(List elems) {
        ListElement last = (ListElement) ListUtil.getLast(elems);
        if (last.isPenalty() && ((KnuthPenalty)last).getPenalty() < KnuthElement.INFINITE) {
            return true;
        } else if (last instanceof BreakElement
                && ((BreakElement)last).getPenaltyValue() < KnuthElement.INFINITE) {
            return true;
        }
        return false;
    }

    
Determines the position of the previous break before the start index on an
element list.
Params:
elems – the element list
startIndex – the start index
Returns:
the position of the previous break, or -1 if there was no previous break/**
     * Determines the position of the previous break before the start index on an
     * element list.
     * @param elems the element list
     * @param startIndex the start index
     * @return the position of the previous break, or -1 if there was no previous break
     */
    public static int determinePreviousBreak(List elems, int startIndex) {
        int prevBreak = startIndex - 1;
        while (prevBreak >= 0) {
            KnuthElement el = (KnuthElement)elems.get(prevBreak);
            if (el.isPenalty() && el.getPenalty() < KnuthElement.INFINITE) {
                break;
            }
            prevBreak--;
        }
        return prevBreak;
    }

    public static boolean isEmptyBox(List elements) {
        if (elements.size() == 1 && elements.get(0) instanceof KnuthBox) {
            KnuthBox kb = (KnuthBox) elements.get(0);
            if (kb.getWidth() == 0) {
                return true;
            }
        }
        return false;
    }
}