/**
 * Base Class for HBoxLayout and VBoxLayout Classes. Generally it should not need to be used directly.
 */
Ext.define('Ext.layout.container.Box', {

    /* Begin Definitions */

    alias: ['layout.box'],
    extend: 'Ext.layout.container.Container',
    alternateClassName: 'Ext.layout.BoxLayout',

    requires: [
        'Ext.layout.container.boxOverflow.None',
        'Ext.layout.container.boxOverflow.Menu',
        'Ext.layout.container.boxOverflow.Scroller',
        'Ext.util.Format',
        'Ext.dd.DragDropManager'
    ],

    /* End Definitions */

    /**
     * @cfg {Object} defaultMargins
     * If the individual contained items do not have a margins property specified or margin specified via CSS, the
     * default margins from this property will be applied to each item.
     *
     * This property may be specified as an object containing margins to apply in the format:
     *
     *     {
     *         top: (top margin),
     *         right: (right margin),
     *         bottom: (bottom margin),
     *         left: (left margin)
     *     }
     *
     * This property may also be specified as a string containing space-separated, numeric margin values. The order of
     * the sides associated with each value matches the way CSS processes margin values:
     *
     *   - If there is only one value, it applies to all sides.
     *   - If there are two values, the top and bottom borders are set to the first value and the right and left are
     *     set to the second.
     *   - If there are three values, the top is set to the first value, the left and right are set to the second,
     *     and the bottom is set to the third.
     *   - If there are four values, they apply to the top, right, bottom, and left, respectively.
     */
    defaultMargins: {
        top: 0,
        right: 0,
        bottom: 0,
        left: 0
    },

    /**
     * @cfg {String} padding
     * Sets the padding to be applied to all child items managed by this layout.
     *
     * This property must be specified as a string containing space-separated, numeric padding values. The order of the
     * sides associated with each value matches the way CSS processes padding values:
     *
     *   - If there is only one value, it applies to all sides.
     *   - If there are two values, the top and bottom borders are set to the first value and the right and left are
     *     set to the second.
     *   - If there are three values, the top is set to the first value, the left and right are set to the second,
     *     and the bottom is set to the third.
     *   - If there are four values, they apply to the top, right, bottom, and left, respectively.
     */
    padding: 0,

    /**
     * @cfg {String} pack
     * Controls how the child items of the container are packed together. Acceptable configuration values for this
     * property are:
     *
     *   - **start** - child items are packed together at **left** (HBox) or **top** (VBox) side of container (*default**)
     *   - **center** - child items are packed together at **mid-width** (HBox) or **mid-height** (VBox) of container
     *   - **end** - child items are packed together at **right** (HBox) or **bottom** (VBox) side of container
     */
    pack: 'start',

    /**
     * @cfg {Number} flex
     * This configuration option is to be applied to **child items** of the container managed by this layout. Each child
     * item with a flex property will be flexed (horizontally in `hbox`, vertically in `vbox`) according to each item's
     * **relative** flex value compared to the sum of all items with a flex value specified. Any child items that have
     * either a `flex = 0` or `flex = undefined` will not be 'flexed' (the initial size will not be changed).
     */
    flex: undefined,

    /**
     * @cfg {String/Ext.Component} stretchMaxPartner
     * Allows stretchMax calculation to take into account the max perpendicular size (height for HBox layout and width
     * for VBox layout) of another Box layout when calculating its maximum perpendicular child size.
     *
     * If specified as a string, this may be either a known Container ID, or a ComponentQuery selector which is rooted
     * at this layout's Container (ie, to find a sibling, use `"^>#siblingItemId`).
     */
    stretchMaxPartner: undefined,

    type: 'box',
    scrollOffset: 0,
    itemCls: Ext.baseCSSPrefix + 'box-item',
    targetCls: Ext.baseCSSPrefix + 'box-layout-ct',
    innerCls: Ext.baseCSSPrefix + 'box-inner',

    // availableSpaceOffset is used to adjust the availableWidth, typically used
    // to reserve space for a scrollbar
    availableSpaceOffset: 0,

    // whether or not to reserve the availableSpaceOffset in layout calculations
    reserveOffset: true,

    manageMargins: true,
    
    createsInnerCt: true,

    childEls: [
        'innerCt',
        'targetEl'
    ],

    renderTpl: [
        '{%var oc,l=values.$comp.layout,oh=l.overflowHandler;',
        'if (oh.getPrefixConfig!==Ext.emptyFn) {',
            'if(oc=oh.getPrefixConfig())dh.generateMarkup(oc, out)',
        '}%}',
        '<div id="{ownerId}-innerCt" class="{[l.innerCls]} {[oh.getOverflowCls()]}" role="presentation">',
            '<div id="{ownerId}-targetEl" style="position:absolute;',
                    // This width for the "CSS container box" of the box child items gives
                    // them the room they need to avoid being "crushed" (aka, "wrapped").
                    // On Opera, elements cannot be wider than 32767px or else they break
                    // the scrollWidth (it becomes == offsetWidth) and you cannot scroll
                    // the content.
                    'width:20000px;',
                    // On IE quirks and IE6/7 strict, a text-align:center style trickles
                    // down to this el at times and will cause it to move off the left edge.
                    // The easy fix is to just always set left:0px here (right:0px in rtl
                    // mode). The top:0px part is just being paranoid. The requirement for
                    // targetEl is that its origin align with innerCt... this ensures that
                    // it does!
                    '{[values.$layout.names.beforeX]}:0px;{[values.$layout.names.beforeY]}:0px;',
                    // If we don't give the element a height, it does not always participate
                    // in the scrollWidth.
                    'height:1px"<tpl if="targetCls"> class="{targetCls}"</tpl>>',
                '{%this.renderBody(out, values)%}',
            '</div>',
        '</div>',
        '{%if (oh.getSuffixConfig!==Ext.emptyFn) {',
            'if(oc=oh.getSuffixConfig())dh.generateMarkup(oc, out)',
        '}%}',
        {
            disableFormats: true,
            definitions: 'var dh=Ext.DomHelper;'
        }
    ],

    constructor: function(config) {
        var me = this,
            type;

        me.callParent(arguments);

        // The sort function needs access to properties in this, so must be bound.
        me.flexSortFn = Ext.Function.bind(me.flexSort, me);

        me.initOverflowHandler();

        type = typeof me.padding;
        if (type == 'string' || type == 'number') {
            me.padding = Ext.util.Format.parseBox(me.padding);
            me.padding.height = me.padding.top  + me.padding.bottom;
            me.padding.width  = me.padding.left + me.padding.right;
        }
    },

    // Matches: <spaces>digits[.digits]<spaces>%<spaces>
    // Captures: digits[.digits]
    _percentageRe: /^\s*(\d+(?:\.\d*)?)\s*[%]\s*$/,

    getItemSizePolicy: function (item, ownerSizeModel) {
        var me = this,
            policy = me.sizePolicy,
            align = me.align,
            flex = item.flex,
            key = align,
            names = me.names,
            width = item[names.width],
            height = item[names.height],
            percentageRe = me._percentageRe,
            percentageWidth = percentageRe.test(width),
            isStretch = (align == 'stretch'),
            isStretchMax = (align == 'stretchmax'),
            constrain = me.constrainAlign;
            
        // Getting the size model is expensive, so we only want to do so if we really need it
        if (!ownerSizeModel && (isStretch || flex || percentageWidth || (constrain && !isStretchMax))) {
            ownerSizeModel = me.owner.getSizeModel();
        }

        if (isStretch) {
            // If we are height.shrinkWrap, we behave as if we were stretchmax (for more
            // details, see beginLayoutCycle)...
            if (!percentageRe.test(height) && ownerSizeModel[names.height].shrinkWrap) {
                key = 'stretchmax';
                // We leave %age height as stretch since it will not participate in the
                // stretchmax size calculation. This avoid running such a child in its
                // shrinkWrap mode prior to supplying the calculated size.
            }
        } else if (!isStretchMax) {
            if (percentageRe.test(height)) {
                // Height %ages are calculated based on container size, so they are the
                // same as align=stretch for this purpose...
                key = 'stretch';
            } else if (constrain && !ownerSizeModel[names.height].shrinkWrap) {
                // Same functionality as stretchmax, only the max is going to be the size
                // of the container, not the largest item
                key = 'stretchmax';
            } else {
                key = '';
            }
        }

        if (flex || percentageWidth) {
            // If we are width.shrinkWrap, we won't be flexing since that requires a
            // container width...
            if (!ownerSizeModel[names.width].shrinkWrap) {
                policy = policy.flex; // both flex and %age width are calculated
            }
        }

        return policy[key];
    },

    flexSort: function (a, b) {
        // We need to sort the flexed items to ensure that we have
        // the items with max/min width first since when we set the
        // values we may have the value constrained, so we need to
        // react accordingly. Precedence is given from the largest
        // value through to the smallest value
        var maxWidthName = this.names.maxWidth,
            minWidthName = this.names.minWidth,
            infiniteValue = Infinity,
            aTarget = a.target,
            bTarget = b.target,
            result = 0,
            aMin, bMin, aMax, bMax,
            hasMin, hasMax;

        aMax = aTarget[maxWidthName] || infiniteValue;
        bMax = bTarget[maxWidthName] || infiniteValue;
        aMin = aTarget[minWidthName] || 0;
        bMin = bTarget[minWidthName] || 0;
        
        hasMin = isFinite(aMin) || isFinite(bMin);
        hasMax = isFinite(aMax) || isFinite(bMax);

        if (hasMin || hasMax) {
            if (hasMax) {
                result = aMax - bMax;
            }
            
            // If the result is 0, it means either
            // a) hasMax was false
            // b) The max values were the same
            if (result === 0 && hasMin) {
                result = bMin - aMin;
            }
        }
        return result;
    },

    isItemBoxParent: function (itemContext) {
        return true;
    },

    isItemShrinkWrap: function (item) {
        return true;
    },

    roundFlex: function(width) {
        return Math.ceil(width);
    },

    /**
     * @private
     * Called by an owning Panel before the Panel begins its collapse process.
     * Most layouts will not need to override the default Ext.emptyFn implementation.
     */
    beginCollapse: function(child) {
        var me = this;

        if (me.direction === 'vertical' && child.collapsedVertical()) {
            child.collapseMemento.capture(['flex']);
            delete child.flex;
        } else if (me.direction === 'horizontal' && child.collapsedHorizontal()) {
            child.collapseMemento.capture(['flex']);
            delete child.flex;
        }
    },

    /**
     * @private
     * Called by an owning Panel before the Panel begins its expand process.
     * Most layouts will not need to override the default Ext.emptyFn implementation.
     */
    beginExpand: function(child) {

        // Restores the flex if we used to be flexed before
        child.collapseMemento.restore(['flex']);
    },

    beginLayout: function (ownerContext) {
        var me = this,
            owner = me.owner,
            smp = owner.stretchMaxPartner,
            style = me.innerCt.dom.style,
            names = me.names;

        ownerContext.boxNames = names;

        // this must happen before callParent to allow the overflow handler to do its work
        // that can effect the childItems collection...
        me.overflowHandler.beginLayout(ownerContext);

        // get the contextItem for our stretchMax buddy:
        if (typeof smp === 'string') {
            smp = Ext.getCmp(smp) || owner.query(smp)[0];
        }

        ownerContext.stretchMaxPartner = smp && ownerContext.context.getCmp(smp);

        me.callParent(arguments);

        ownerContext.innerCtContext = ownerContext.getEl('innerCt', me);

        // Capture whether the owning Container is scrolling in the parallel direction
        me.scrollParallel = owner.scrollFlags[names.x];

        // Capture whether the owning Container is scrolling in the perpendicular direction
        me.scrollPerpendicular = owner.scrollFlags[names.y];

        // If we *are* scrolling parallel, capture the scroll position of the encapsulating element
        if (me.scrollParallel) {
            me.scrollPos = owner.getTargetEl().dom[names.scrollLeft];
        }

        // Don't allow sizes burned on to the innerCt to influence measurements.
        style.width = '';
        style.height = '';
    },

    beginLayoutCycle: function (ownerContext, firstCycle) {
        var me = this,
            align = me.align,
            names = ownerContext.boxNames,
            pack = me.pack,
            heightModelName = names.heightModel;

        // this must happen before callParent to allow the overflow handler to do its work
        // that can effect the childItems collection...
        me.overflowHandler.beginLayoutCycle(ownerContext, firstCycle);

        me.callParent(arguments);

        // Cache several of our string concat/compare results (since width/heightModel can
        // change if we are invalidated, we cannot do this in beginLayout)

        ownerContext.parallelSizeModel      = ownerContext[names.widthModel];
        ownerContext.perpendicularSizeModel = ownerContext[heightModelName];

        ownerContext.boxOptions = {
            align: align = {
                stretch:    align == 'stretch',
                stretchmax: align == 'stretchmax',
                center:     align == names.center,
                bottom:     align == names.afterY
            },
            pack: pack = {
                center: pack == 'center',
                end:    pack == 'end'
            }
        };

        // Consider an hbox w/stretch which means "assign all items the container's height".
        // The spirit of this request is make all items the same height, but when shrinkWrap
        // height is also requested, the height of the tallest item determines the height.
        // This is exactly what the stretchmax option does, so we jiggle the flags here to
        // act as if stretchmax were requested.

        if (align.stretch && ownerContext.perpendicularSizeModel.shrinkWrap) {
            align.stretchmax = true;
            align.stretch = false;
        }

        // This is handy for knowing that we might need to apply height %ages
        align.nostretch = !(align.stretch || align.stretchmax);

        // In our example hbox, packing items to the right (end) or center can only work if
        // there is a container width. So, if we are shrinkWrap, we just turn off the pack
        // options for the run.

        if (ownerContext.parallelSizeModel.shrinkWrap) {
            pack.center = pack.end = false;
        }

        me.cacheFlexes(ownerContext);

        // In Webkit and IE we set the width of the target el equal to the width of the innerCt
        // when the layout cycle is finished, so we need to set it back to 20000px here
        // to prevent the children from being crushed.
        // IE needs it because of its scrollIntoView bug: https://sencha.jira.com/browse/EXTJSIV-6520
        // Webkit needs it because of its mouse drag bug: https://sencha.jira.com/browse/EXTJSIV-5962
        if (Ext.isWebKit || Ext.isIE) {
            me.targetEl.setWidth(20000);
        }
    },

    /**
     * This method is called to (re)cache our understanding of flexes. This happens during beginLayout and may need to
     * be called again if the flexes are changed during the layout (e.g., like ColumnLayout).
     * @param {Object} ownerContext
     * @protected
     */
    cacheFlexes: function (ownerContext) {
        var me = this,
            names = ownerContext.boxNames,
            widthModelName = names.widthModel,
            heightModelName = names.heightModel,
            nostretch = ownerContext.boxOptions.align.nostretch,
            totalFlex = 0,
            childItems = ownerContext.childItems,
            i = childItems.length,
            flexedItems = [],
            minWidth = 0,
            minWidthName = names.minWidth,
            percentageRe = me._percentageRe,
            percentageWidths = 0,
            percentageHeights = 0,
            child, childContext, flex, match;

        while (i--) {
            childContext = childItems[i];
            child = childContext.target;

            // check widthModel to see if we are the sizing layout. If so, copy the flex
            // from the item to the contextItem and add it to totalFlex
            //
            if (childContext[widthModelName].calculated) {
                childContext.flex = flex = child.flex;
                if (flex) {
                    totalFlex += flex;
                    flexedItems.push(childContext);
                    minWidth += child[minWidthName] || 0;
                } else { // a %age width...
                    match = percentageRe.exec(child[names.width]);
                    childContext.percentageParallel = parseFloat(match[1]) / 100;
                    ++percentageWidths;
                }
            }
            // the above means that "childContext.flex" is properly truthy/falsy, which is
            // often times quite convenient...

            if (nostretch && childContext[heightModelName].calculated) {
                // the only reason we would be calculated height in this case is due to a
                // height %age...
                match = percentageRe.exec(child[names.height]);
                childContext.percentagePerpendicular = parseFloat(match[1]) / 100;
                ++percentageHeights;
            }
        }

        ownerContext.flexedItems = flexedItems;
        ownerContext.flexedMinSize = minWidth;
        ownerContext.totalFlex = totalFlex;
        ownerContext.percentageWidths = percentageWidths;
        ownerContext.percentageHeights = percentageHeights;

        // The flexed boxes need to be sorted in ascending order of maxSize to work properly
        // so that unallocated space caused by maxWidth being less than flexed width can be
        // reallocated to subsequent flexed boxes.
        Ext.Array.sort(flexedItems, me.flexSortFn);
    },

    calculate: function(ownerContext) {
        var me = this,
            targetSize = me.getContainerSize(ownerContext),
            names = ownerContext.boxNames,
            state = ownerContext.state,
            plan = state.boxPlan || (state.boxPlan = {});

        plan.targetSize = targetSize;

        // If we are not widthModel.shrinkWrap, we need the width before we can lay out boxes:
        if (!ownerContext.parallelSizeModel.shrinkWrap && !targetSize[names.gotWidth]) {
            me.done = false;
            return;
        }

        if (!state.parallelDone) {
            state.parallelDone = me.calculateParallel(ownerContext, names, plan);
        }

        if (!state.perpendicularDone) {
            state.perpendicularDone = me.calculatePerpendicular(ownerContext, names, plan);
        }

        if (state.parallelDone && state.perpendicularDone) {
            // Fix for left and right docked Components in a dock component layout. This is for docked Headers and docked Toolbars.
            // Older Microsoft browsers do not size a position:absolute element's width to match its content.
            // So in this case, in the publishInnerCtSize method we may need to adjust the size of the owning Container's element explicitly based upon
            // the discovered max width. So here we put a calculatedWidth property in the metadata to facilitate this.
            if (me.owner.dock && (Ext.isIE7m || Ext.isIEQuirks) && !me.owner.width && !me.horizontal) {
                plan.isIEVerticalDock = true;
                plan.calculatedWidth = plan.maxSize + ownerContext.getPaddingInfo().width + ownerContext.getFrameInfo().width;
            }

            me.publishInnerCtSize(ownerContext, me.reserveOffset ? me.availableSpaceOffset : 0);

            // Calculate stretchmax only if there is >1 child item
            if (me.done && ownerContext.childItems.length > 1 && ownerContext.boxOptions.align.stretchmax && !state.stretchMaxDone) {
                me.calculateStretchMax(ownerContext, names, plan);
                state.stretchMaxDone = true;
            }
            me.overflowHandler.calculate(ownerContext);
        } else {
            me.done = false;
        }
    },

    calculateParallel: function(ownerContext, names, plan) {
        var me = this,
            widthName = names.width,
            childItems = ownerContext.childItems,
            beforeXName = names.beforeX,
            afterXName = names.afterX,
            setWidthName = names.setWidth,
            childItemsLength = childItems.length,
            flexedItems = ownerContext.flexedItems,
            flexedItemsLength = flexedItems.length,
            pack = ownerContext.boxOptions.pack,
            padding = me.padding,
            containerWidth = plan.targetSize[widthName],
            totalMargin = 0,
            left = padding[beforeXName],
            nonFlexWidth = left + padding[afterXName] + me.scrollOffset +
                                    (me.reserveOffset ? me.availableSpaceOffset : 0),
            scrollbarWidth = Ext.getScrollbarSize()[names.width],
            i, childMargins, remainingWidth, remainingFlex, childContext, flex, flexedWidth,
            contentWidth, mayNeedScrollbarAdjust, childWidth, percentageSpace;

        // We may need to add scrollbar size to parallel size if
        //     Scrollbars take up space
        //     and we are scrolling in the perpendicular direction
        //     and shrinkWrapping in the parallel direction,
        //     and NOT stretching perpendicular dimensions to fit
        //     and NOT shrinkWrapping in the perpendicular direction
        if (scrollbarWidth &&
            me.scrollPerpendicular &&
            ownerContext.parallelSizeModel.shrinkWrap &&
            !ownerContext.boxOptions.align.stretch &&
            !ownerContext.perpendicularSizeModel.shrinkWrap) {

            // If its possible that we may need to add scrollbar size to the parallel size
            // then we need to wait until the perpendicular size has been determined,
            // so that we know if there is a scrollbar.
            if (!ownerContext.state.perpendicularDone) {
                return false;
            }
            mayNeedScrollbarAdjust = true;
        }

        // Gather the total size taken up by non-flexed items:
        for (i = 0; i < childItemsLength; ++i) {
            childContext = childItems[i];
            childMargins = childContext.marginInfo || childContext.getMarginInfo();

            totalMargin += childMargins[widthName];

            if (!childContext[names.widthModel].calculated) {
                childWidth = childContext.getProp(widthName);
                nonFlexWidth += childWidth; // min/maxWidth safe
                if (isNaN(nonFlexWidth)) {
                    return false;
                }
            }
        }

        nonFlexWidth += totalMargin;
        if (ownerContext.percentageWidths) {
            percentageSpace = containerWidth - totalMargin;
            if (isNaN(percentageSpace)) {
                return false;
            }

            for (i = 0; i < childItemsLength; ++i) {
                childContext = childItems[i];
                if (childContext.percentageParallel) {
                    childWidth = Math.ceil(percentageSpace * childContext.percentageParallel);
                    childWidth = childContext.setWidth(childWidth);
                    nonFlexWidth += childWidth;
                }
            }
        }

        // if we get here, we have all the childWidths for non-flexed items...

        if (ownerContext.parallelSizeModel.shrinkWrap) {
            plan.availableSpace = 0;
            plan.tooNarrow = false;
        } else {
            plan.availableSpace = containerWidth - nonFlexWidth;

            // If we're going to need space for a parallel scrollbar, then we need to redo the perpendicular measurements
            plan.tooNarrow = plan.availableSpace < ownerContext.flexedMinSize;
            if (plan.tooNarrow && Ext.getScrollbarSize()[names.height] && me.scrollParallel && ownerContext.state.perpendicularDone) {
                ownerContext.state.perpendicularDone = false;
                for (i = 0; i < childItemsLength; ++i) {
                    childItems[i].invalidate();
                }
            }
        }

        contentWidth = nonFlexWidth;
        remainingWidth = plan.availableSpace;
        remainingFlex = ownerContext.totalFlex;

        // Calculate flexed item sizes:
        for (i = 0; i < flexedItemsLength; i++) {
            childContext = flexedItems[i];
            flex         = childContext.flex;
            flexedWidth  = me.roundFlex((flex / remainingFlex) * remainingWidth);
            flexedWidth  = childContext[setWidthName](flexedWidth); // constrained

            // due to minWidth constraints, it may be that flexedWidth > remainingWidth

            contentWidth   += flexedWidth;
            // Remaining space has already had margins subtracted, so just subtract size
            remainingWidth  = Math.max(0, remainingWidth - flexedWidth); // no negatives!
            remainingFlex  -= flex;
        }

        if (pack.center) {
            left += remainingWidth / 2;

            // If content is too wide to pack to center, do not allow the centering calculation to place it off the left edge.
            if (left < 0) {
                left = 0;
            }
        } else if (pack.end) {
            left += remainingWidth;
        }

        // Assign parallel position for the boxes:
        for (i = 0; i < childItemsLength; ++i) {
            childContext = childItems[i];
            childMargins = childContext.marginInfo; // already cached by first loop

            left += childMargins[beforeXName];

            childContext.setProp(names.x, left);

            // We can read directly from "props.width" because we have already properly
            // requested it in the calculation of nonFlexedWidths or we calculated it.
            // We cannot call getProp because that would be inappropriate for flexed items
            // and we don't need any extra function call overhead:
            left += childMargins[afterXName] + childContext.props[widthName];
        }

        contentWidth += ownerContext.targetContext.getPaddingInfo()[widthName];

        // Stash the contentWidth on the state so that it can always be accessed later in the calculation
        ownerContext.state.contentWidth = contentWidth; 

        // if there is perpendicular overflow, the published parallel content size includes
        // the size of the perpendicular scrollbar.
        if (mayNeedScrollbarAdjust &&
            (ownerContext.peek(names.contentHeight) > plan.targetSize[names.height])) {
            contentWidth += scrollbarWidth;
            ownerContext[names.hasOverflowY] = true;

            // tell the component layout to set the parallel size in the dom
            ownerContext.target.componentLayout[names.setWidthInDom] = true;

            // IE8 in what passes for "strict" mode will not create a scrollbar if 
            // there is just the *exactly correct* spare space created for it. We
            // have to force that to happen once all the styles have been flushed
            // to the DOM (see completeLayout):
            ownerContext[names.invalidateScrollY] = Ext.isStrict && Ext.isIE8;
        }
        ownerContext[names.setContentWidth](contentWidth);

        return true;
    },

    calculatePerpendicular: function(ownerContext, names, plan) {
        var me = this,
            heightShrinkWrap = ownerContext.perpendicularSizeModel.shrinkWrap,
            targetSize = plan.targetSize,
            childItems = ownerContext.childItems,
            childItemsLength = childItems.length,
            mmax = Math.max,
            heightName = names.height,
            setHeightName = names.setHeight,
            beforeYName = names.beforeY,
            topPositionName = names.y,
            padding = me.padding,
            top = padding[beforeYName],
            availHeight = targetSize[heightName] - top - padding[names.afterY],
            align = ownerContext.boxOptions.align,
            isStretch    = align.stretch, // never true if heightShrinkWrap (see beginLayoutCycle)
            isStretchMax = align.stretchmax,
            isCenter     = align.center,
            isBottom     = align.bottom,
            constrain    = me.constrainAlign,
            maxHeight = 0,
            hasPercentageSizes = 0,
            onBeforeInvalidateChild = me.onBeforeConstrainInvalidateChild,
            onAfterInvalidateChild = me.onAfterConstrainInvalidateChild,
            scrollbarHeight = Ext.getScrollbarSize().height,
            childTop, i, childHeight, childMargins, diff, height, childContext,
            stretchMaxPartner, stretchMaxChildren, shrinkWrapParallelOverflow, 
            percentagePerpendicular;

        if (isStretch || ((isCenter || isBottom) && !heightShrinkWrap)) {
            if (isNaN(availHeight)) {
                return false;
            }
        }

        // If the intention is to horizontally scroll child components, but the container is too narrow,
        // then:
        //     if we are shrinkwrapping height:
        //         Set a flag because we are going to expand the height taken by the perpendicular dimension to accommodate the scrollbar
        //     else
        //         We must allow for the parallel scrollbar to intrude into the height
        if (me.scrollParallel && plan.tooNarrow) {
            if (heightShrinkWrap) {
                shrinkWrapParallelOverflow = true;
            } else {
                availHeight -= scrollbarHeight;
                plan.targetSize[heightName] -= scrollbarHeight;
            }
        }

        if (isStretch) {
            height = availHeight; // never heightShrinkWrap...
        } else {
            for (i = 0; i < childItemsLength; i++) {
                childContext = childItems[i];
                childMargins = (childContext.marginInfo || childContext.getMarginInfo())[heightName];

                if (!(percentagePerpendicular = childContext.percentagePerpendicular)) {
                    childHeight = childContext.getProp(heightName);
                } else {
                    ++hasPercentageSizes;
                    if (heightShrinkWrap) {
                        // height %age items cannot contribute to maxHeight... they are going
                        // to be a %age of that maxHeight!
                        continue;
                    } else {
                        childHeight = percentagePerpendicular * availHeight - childMargins;
                        childHeight = childContext[names.setHeight](childHeight);
                    }
                }
                
                // Summary:
                // 1) Not shrink wrapping height, so the height is not determined by the children
                // 2) Constrain is set
                // 3) The child item is shrink wrapping
                // 4) It execeeds the max
                if (!heightShrinkWrap && constrain && childContext[names.heightModel].shrinkWrap && childHeight > availHeight) {
                    childContext.invalidate({
                        before: onBeforeInvalidateChild,
                        after: onAfterInvalidateChild,
                        layout: me,
                        childHeight: availHeight,
                        names: names
                    });
                    
                    // By invalidating the height, it could mean the width can change, so we need
                    // to recalculate in the parallel direction.
                    ownerContext.state.parallelDone = false; 
                }

                // Max perpendicular measurement (used for stretchmax) must take the min perpendicular size of each child into account in case any fall short.
                if (isNaN(maxHeight = mmax(maxHeight, childHeight + childMargins,
                                           childContext.target[names.minHeight] || 0))) {
                    return false; // heightShrinkWrap || isCenter || isStretchMax ??
                }
            }

            // If there is going to be a parallel scrollbar maxHeight must include it to the outside world.
            // ie: a stretchmaxPartner, and the setContentHeight
            if (shrinkWrapParallelOverflow) {
                maxHeight += scrollbarHeight;
                ownerContext[names.hasOverflowX] = true;

                // tell the component layout to set the perpendicular size in the dom
                ownerContext.target.componentLayout[names.setHeightInDom] = true;

                // IE8 in what passes for "strict" mode will not create a scrollbar if 
                // there is just the *exactly correct* spare space created for it. We
                // have to force that to happen once all the styles have been flushed
                // to the DOM (see completeLayout):
                ownerContext[names.invalidateScrollX] = Ext.isStrict && Ext.isIE8;
            }

            // If we are associated with another box layout, grab its maxChildHeight
            // This must happen before we calculate and publish our contentHeight
            stretchMaxPartner = ownerContext.stretchMaxPartner;
            if (stretchMaxPartner) {
                // Publish maxChildHeight as soon as it has been calculated for our partner:
                ownerContext.setProp('maxChildHeight', maxHeight);
                stretchMaxChildren = stretchMaxPartner.childItems;
                // Only wait for maxChildHeight if our partner has visible items:
                if (stretchMaxChildren && stretchMaxChildren.length) {
                    maxHeight = mmax(maxHeight, stretchMaxPartner.getProp('maxChildHeight'));
                    if (isNaN(maxHeight)) {
                        return false;
                    }
                }
            }

            ownerContext[names.setContentHeight](maxHeight + me.padding[heightName] +
                    ownerContext.targetContext.getPaddingInfo()[heightName]);

            // We have to publish the contentHeight with the additional scrollbarHeight
            // to encourage our container to accomodate it, but we must remove the height
            // of the scrollbar as we go to sizing or centering the children.
            if (shrinkWrapParallelOverflow) {
                maxHeight -= scrollbarHeight;
            }
            plan.maxSize = maxHeight;

            if (isStretchMax) {
                height = maxHeight;
            } else if (isCenter || isBottom || hasPercentageSizes) {
                if (constrain) {
                    height = heightShrinkWrap ? maxHeight : availHeight;
                } else {
                    height = heightShrinkWrap ? maxHeight : mmax(availHeight, maxHeight);
                }

                // When calculating a centered position within the content box of the innerCt,
                // the width of the borders must be subtracted from the size to yield the
                // space available to center within. The publishInnerCtSize method explicitly
                // adds the border widths to the set size of the innerCt.
                height -= ownerContext.innerCtContext.getBorderInfo()[heightName];
            }
        }

        for (i = 0; i < childItemsLength; i++) {
            childContext = childItems[i];
            childMargins = childContext.marginInfo || childContext.getMarginInfo();

            childTop = top + childMargins[beforeYName];

            if (isStretch) {
                childContext[setHeightName](height - childMargins[heightName]);
            } else {
                percentagePerpendicular = childContext.percentagePerpendicular;
                if (heightShrinkWrap && percentagePerpendicular) {
                    childMargins = childContext.marginInfo || childContext.getMarginInfo();
                    childHeight = percentagePerpendicular * height - childMargins[heightName];
                    childHeight = childContext.setHeight(childHeight);
                }

                if (isCenter) {
                    diff = height - childContext.props[heightName];
                    if (diff > 0) {
                        childTop = top + Math.round(diff / 2);
                    }
                } else if (isBottom) {
                    childTop = mmax(0, height - childTop - childContext.props[heightName]);
                }
            }

            childContext.setProp(topPositionName, childTop);
        }

        return true;
    },
    
    onBeforeConstrainInvalidateChild: function(childContext, options){
        // NOTE: No "this" pointer in here...
        var heightModelName = options.names.heightModel;
        if (!childContext[heightModelName].constrainedMin) {
            // if the child hit a min constraint, it needs to be at its configured size, so
            // we leave the sizeModel alone
            childContext[heightModelName] = Ext.layout.SizeModel.calculated;
        }
    },
    
    onAfterConstrainInvalidateChild: function(childContext, options){
         // NOTE: No "this" pointer in here...
        var names = options.names;

        // We use 0 here because we know the size exceeds the available size.
        // This was chosen on purpose, even for align: 'bottom', because it doesn't
        // make practical sense to place the item at the bottom and then have it overflow
        // over the top of the container, since it's not possible to scroll to it. As such,
        // we always put the component at the top to follow normal document flow.
        childContext.setProp(names.beforeY, 0);
        if (childContext[names.heightModel].calculated) {
            childContext[names.setHeight](options.childHeight);
        }
    },

    calculateStretchMax: function (ownerContext, names, plan) {
        var me = this,
            heightName = names.height,
            widthName = names.width,
            childItems = ownerContext.childItems,
            length = childItems.length,
            height = plan.maxSize,
            onBeforeStretchMaxInvalidateChild = me.onBeforeStretchMaxInvalidateChild,
            onAfterStretchMaxInvalidateChild = me.onAfterStretchMaxInvalidateChild,
            childContext, props, i, childHeight;

        for (i = 0; i < length; ++i) {
            childContext = childItems[i];

            props = childContext.props;
            childHeight = height - childContext.getMarginInfo()[heightName];

            if (childHeight != props[heightName] ||   // if (wrong height ...
                childContext[names.heightModel].constrained) { // ...or needs invalidation)
                // When we invalidate a child, since we won't be around to size or position
                // it, we include an after callback that will be run after the invalidate
                // that will (re)do that work. The good news here is that we can read the
                // results of all that from the childContext props.
                //
                // We also include a before callback to change the sizeModel to calculated
                // prior to the layout being invoked.
                childContext.invalidate({
                    before: onBeforeStretchMaxInvalidateChild,
                    after: onAfterStretchMaxInvalidateChild,
                    layout: me,
                    // passing this data avoids a 'scope' and its Function.bind
                    childWidth: props[widthName],
                    // subtract margins from the maximum value
                    childHeight: childHeight,
                    childX: props.x,
                    childY: props.y,
                    names: names
                });
            }
        }
    },
    
    onBeforeStretchMaxInvalidateChild: function (childContext, options) {
        // NOTE: No "this" pointer in here...
        var heightModelName = options.names.heightModel;

        // Change the childItem to calculated (i.e., "set by ownerCt"). The component layout
        // of the child can course-correct (like dock layout does for a collapsed panel),
        // so we must make these changes here before that layout's beginLayoutCycle is
        // called.
        if (!childContext[heightModelName].constrainedMax) {
            // if the child hit a max constraint, it needs to be at its configured size, so
            // we leave the sizeModel alone...
            childContext[heightModelName] = Ext.layout.SizeModel.calculated;
        }
    },

    onAfterStretchMaxInvalidateChild: function (childContext, options) {
        // NOTE: No "this" pointer in here...
        var names = options.names,
            childHeight = options.childHeight,
            childWidth = options.childWidth;

        childContext.setProp('x', options.childX);
        childContext.setProp('y', options.childY);

        if (childContext[names.heightModel].calculated) {
            // We need to respect a child that is still not calculated (such as a collapsed
            // panel)...
            childContext[names.setHeight](childHeight);
        }

        if (childContext[names.widthModel].calculated) {
            childContext[names.setWidth](childWidth);
        }
    },

    completeLayout: function(ownerContext) {
        var me = this,
            names = ownerContext.boxNames,
            invalidateScrollX = ownerContext.invalidateScrollX,
            invalidateScrollY = ownerContext.invalidateScrollY,
            dom, el, overflowX, overflowY, styles;

        me.overflowHandler.completeLayout(ownerContext);

        if (invalidateScrollX || invalidateScrollY) {
            el = me.getTarget();
            dom = el.dom;
            styles = dom.style;

            if (invalidateScrollX) {
                // get computed style to see if we are 'auto'
                overflowX = el.getStyle('overflowX');
                if (overflowX == 'auto') {
                    // capture the inline style (if any) so we can restore it later:
                    overflowX = styles.overflowX;
                    styles.overflowX = 'scroll'; // force the scrollbar to appear
                } else {
                    invalidateScrollX = false; // no work really since not 'auto'
                }
            }

            if (invalidateScrollY) {
                // get computed style to see if we are 'auto'
                overflowY = el.getStyle('overflowY');
                if (overflowY == 'auto') {
                    // capture the inline style (if any) so we can restore it later:
                    overflowY = styles.overflowY;
                    styles.overflowY = 'scroll'; // force the scrollbar to appear
                } else {
                    invalidateScrollY = false; // no work really since not 'auto'
                }
            }

            if (invalidateScrollX || invalidateScrollY) { // if (some form of 'auto' in play)
                // force a reflow...
                dom.scrollWidth;

                if (invalidateScrollX) {
                    styles.overflowX = overflowX; // restore inline style
                }
                if (invalidateScrollY) {
                    styles.overflowY = overflowY; // restore inline style
                }
            }
        }

        // If we are scrolling parallel, restore the saved scroll position
        if (me.scrollParallel) {
            me.owner.getTargetEl().dom[names.scrollLeft] = me.scrollPos;
        }
    },

    finishedLayout: function(ownerContext) {
        this.overflowHandler.finishedLayout(ownerContext);
        this.callParent(arguments);

        // Fix for an obscure webkit bug (EXTJSIV-5962) caused by the targetEl's 20000px
        // width.  We set a very large width on the targetEl at the beginning of the 
        // layout cycle to prevent any "crushing" effect on the child items, however
        // in some cases the very large width makes it possible to scroll the innerCt
        // by dragging on certain child elements. To prevent this from happening we ensure
        // that the targetEl's width is the same as the innerCt.
        // IE needs it because of its scrollIntoView bug: https://sencha.jira.com/browse/EXTJSIV-6520
        // Webkit needs it because of its mouse drag bug: https://sencha.jira.com/browse/EXTJSIV-5962
        if (Ext.isWebKit || Ext.isIE) {
            this.targetEl.setWidth(ownerContext.innerCtContext.props.width);
        }
    },

    publishInnerCtSize: function(ownerContext, reservedSpace) {
        var me = this,
            names = ownerContext.boxNames,
            heightName = names.height,
            widthName = names.width,
            align = ownerContext.boxOptions.align,
            dock = me.owner.dock,
            padding = me.padding,
            plan = ownerContext.state.boxPlan,
            targetSize = plan.targetSize,
            height = targetSize[heightName],
            innerCtContext = ownerContext.innerCtContext,
            innerCtWidth = (ownerContext.parallelSizeModel.shrinkWrap || (plan.tooNarrow && me.scrollParallel)
                    ? ownerContext.state.contentWidth - ownerContext.targetContext.getPaddingInfo()[widthName]
                    : targetSize[widthName]) - (reservedSpace || 0),
            innerCtHeight;

        if (align.stretch) {
            innerCtHeight = height;
        } else {
            innerCtHeight = plan.maxSize + padding[names.beforeY] + padding[names.afterY] + innerCtContext.getBorderInfo()[heightName];

            if (!ownerContext.perpendicularSizeModel.shrinkWrap && (align.center || align.bottom)) {
                innerCtHeight = Math.max(height, innerCtHeight);
            }
        }

        innerCtContext[names.setWidth](innerCtWidth);
        innerCtContext[names.setHeight](innerCtHeight);

        // If unable to publish both dimensions, this layout needs to run again
        if (isNaN(innerCtWidth + innerCtHeight)) {
            me.done = false;
        }

        // If a calculated width has been found (this only happens for widthModel.shrinkWrap
        // vertical docked Components in old Microsoft browsers) then, if the Component has
        // not assumed the size of its content, set it to do so.
        //
        // We MUST pass the dirty flag to get that into the DOM, and because we are a Container
        // layout, and not really supposed to perform sizing, we must also use the force flag.
        if (plan.calculatedWidth && (dock == 'left' || dock == 'right')) {
            // TODO: setting the owner size should be the job of the component layout.
            ownerContext.setWidth(plan.calculatedWidth, true, true);
        }
    },

    onRemove: function(comp){
        var me = this;
        me.callParent(arguments);
        if (me.overflowHandler) {
            me.overflowHandler.onRemove(comp);
        }
        if (comp.layoutMarginCap == me.id) {
            delete comp.layoutMarginCap;
        }
    },

    /**
     * @private
     */
    initOverflowHandler: function() {
        var me = this,
            handler = me.overflowHandler,
            handlerType,
            constructor;

        if (typeof handler == 'string') {
            handler = {
                type: handler
            };
        }

        handlerType = 'None';
        if (handler && handler.type !== undefined) {
            handlerType = handler.type;
        }

        constructor = Ext.layout.container.boxOverflow[handlerType];
        if (constructor[me.type]) {
            constructor = constructor[me.type];
        }

        me.overflowHandler = Ext.create('Ext.layout.container.boxOverflow.' + handlerType, me, handler);
    },

    // Overridden method from Ext.layout.container.Container.
    // Used in the beforeLayout method to render all items into.
    getRenderTarget: function() {
        return this.targetEl;
    },

    // Overridden method from Ext.layout.container.Container.
    // Used by Container classes to insert special DOM elements which must exist in addition to the child components
    getElementTarget: function() {
        return this.innerCt;
    },

    //<debug>
    calculateChildBox: Ext.deprecated(),
    calculateChildBoxes: Ext.deprecated(),
    updateChildBoxes: Ext.deprecated(),
    //</debug>

    /**
     * @private
     */
    destroy: function() {
        Ext.destroy(this.innerCt, this.overflowHandler);
        this.callParent(arguments);
    }
});
