TUITableView.m

/*
 Copyright 2011 Twitter, Inc.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this work except in compliance with the License.
 You may obtain a copy of the License in the LICENSE file, or 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.
 */

#import "TUITableView.h"
#import "TUITableView+Cell.h"
#import "TUINSView.h"

typedef struct {
	CGFloat offset; // from beginning of section
	CGFloat height;
} TUITableViewRowInfo;

@interface TUITableViewSection : NSObject
{
	TUITableView         *_tableView;   // weak
	TUIView              *_headerView;  // Not reusable (similar to UITableView)
	NSInteger             sectionIndex;
	NSUInteger            numberOfRows;
	CGFloat               sectionHeight;
	CGFloat               sectionOffset;
	TUITableViewRowInfo  *rowInfo;
}

@property (readonly) TUIView           *headerView;
@property (nonatomic, assign) CGFloat   sectionOffset;
@property (readonly) NSInteger          sectionIndex;

@end

@implementation TUITableViewSection

@synthesize sectionOffset;
@synthesize sectionIndex;

- (id)initWithNumberOfRows:(NSUInteger)n sectionIndex:(NSInteger)s tableView:(TUITableView *)t
{
	if((self = [super init])){
		_tableView = t;
		sectionIndex = s;
		numberOfRows = n;
		rowInfo = calloc(n, sizeof(TUITableViewRowInfo));
	}
	return self;
}

- (void)dealloc
{
	if(rowInfo) free(rowInfo);
	[_headerView release];
	[super dealloc];
}

- (NSUInteger)numberOfRows
{
	return numberOfRows;
}

- (void)_setupRowHeights
{
	sectionHeight = 0.0;
	
	TUIView *header;
	if((header = self.headerView) != nil) {
		sectionHeight += roundf(header.frame.size.height);
	}
  
	for(int i = 0; i < numberOfRows; ++i) {
		CGFloat h = roundf([_tableView.delegate tableView:_tableView heightForRowAtIndexPath:[TUIFastIndexPath indexPathForRow:i inSection:sectionIndex]]);
		rowInfo[i].offset = sectionHeight;
		rowInfo[i].height = h;
		sectionHeight += h;
	}
	
}

- (CGFloat)rowHeight:(NSInteger)i
{
	if(i >= 0 && i < numberOfRows) {
		return rowInfo[i].height;
	}
	return 0.0;
}

- (CGFloat)sectionRowOffset:(NSInteger)i
{
	if(i >= 0 && i < numberOfRows){
		return rowInfo[i].offset;
	}
	return 0.0;
}

- (CGFloat)tableRowOffset:(NSInteger)i
{
	return sectionOffset + [self sectionRowOffset:i];
}

- (CGFloat)sectionHeight
{
	return sectionHeight;
}

- (CGFloat)headerHeight
{
	return (self.headerView != nil) ? self.headerView.frame.size.height : 0;
}

/**
 * @brief Obtain the section header view.
 * 
 * The section header view is created lazily via the data source when this
 * method is first called.
 * 
 * @return section header view
 */
- (TUIView *)headerView
{
	if(_headerView == nil) {
		if(_tableView.dataSource != nil && [_tableView.dataSource respondsToSelector:@selector(tableView:headerViewForSection:)]){
			_headerView = [[_tableView.dataSource tableView:_tableView headerViewForSection:sectionIndex] retain];
			_headerView.autoresizingMask = TUIViewAutoresizingFlexibleWidth;
		}
	}
	return _headerView;
}

@end

@interface TUITableView (Private)
- (void)_updateDerepeaterViews;
@end

@implementation TUITableView

@synthesize pullDownView=_pullDownView;
@synthesize headerView=_headerView;

- (id)initWithFrame:(CGRect)frame style:(TUITableViewStyle)style
{
	if((self = [super initWithFrame:frame])) {
		_style = style;
		_reusableTableCells = [[NSMutableDictionary alloc] init];
		_visibleSectionHeaders = [[NSMutableIndexSet alloc] init];
		_visibleItems = [[NSMutableDictionary alloc] init];
		_tableFlags.animateSelectionChanges = 1;
	}
	return self;
}

- (id)initWithFrame:(CGRect)frame
{
	return [self initWithFrame:frame style:TUITableViewStylePlain];
}

- (void)dealloc
{
	[_sectionInfo release];
	[_visibleSectionHeaders release];
	[_visibleItems release];
	[_reusableTableCells release];
	[_selectedIndexPath release];
	[_indexPathShouldBeFirstResponder release];
	[_keepVisibleIndexPathForReload release];
	[_pullDownView release];
	[_dragToReorderCell release];
	[_currentDragToReorderIndexPath release];
	[_previousDragToReorderIndexPath release];
	[_headerView release];
	[super dealloc];
}

- (id<TUITableViewDelegate>)delegate
{
	return (id<TUITableViewDelegate>)[super delegate];
}

- (void)setDelegate:(id<TUITableViewDelegate>)d
{
	_tableFlags.delegateTableViewWillDisplayCellForRowAtIndexPath = [d respondsToSelector:@selector(tableView:willDisplayCell:forRowAtIndexPath:)];
	[super setDelegate:d]; // must call super
}

- (id<TUITableViewDataSource>)dataSource
{
	return _dataSource;
}

- (void)setDataSource:(id<TUITableViewDataSource>)d
{
	_dataSource = d;
	_tableFlags.dataSourceNumberOfSectionsInTableView = [_dataSource respondsToSelector:@selector(numberOfSectionsInTableView:)];
}

- (BOOL)animateSelectionChanges
{
	return _tableFlags.animateSelectionChanges;
}

- (void)setAnimateSelectionChanges:(BOOL)a
{
	_tableFlags.animateSelectionChanges = a;
}

- (NSInteger)numberOfSections
{
	return [_sectionInfo count];
}

- (NSInteger)numberOfRowsInSection:(NSInteger)section
{
	return [[_sectionInfo objectAtIndex:section] numberOfRows];
}

- (CGRect)rectForHeaderOfSection:(NSInteger)section {
	if(section >= 0 && section < [_sectionInfo count]){
		TUITableViewSection *s = [_sectionInfo objectAtIndex:section];
		CGFloat offset = [s sectionOffset];
		CGFloat height = [s headerHeight];
		CGFloat y = _contentHeight - offset - height;
		return CGRectMake(0, y, self.bounds.size.width, height);
	}
	return CGRectZero;
}

- (CGRect)rectForSection:(NSInteger)section
{
	if(section >= 0 && section < [_sectionInfo count]){
		TUITableViewSection *s = [_sectionInfo objectAtIndex:section];
		CGFloat offset = [s sectionOffset];
		CGFloat height = [s sectionHeight];
		CGFloat y = _contentHeight - offset - height;
		return CGRectMake(0, y, self.bounds.size.width, height);
	}
	return CGRectZero;
}

- (CGRect)rectForRowAtIndexPath:(TUIFastIndexPath *)indexPath
{
	NSInteger section = indexPath.section;
	NSInteger row = indexPath.row;
	if(section >= 0 && section < [_sectionInfo count]) {
		TUITableViewSection *s = [_sectionInfo objectAtIndex:section];
		CGFloat offset = [s tableRowOffset:row];
		CGFloat height = [s rowHeight:row];
		CGFloat y = _contentHeight - offset - height;
		return CGRectMake(0, y, self.bounds.size.width, height);
	}
	return CGRectZero;
}

- (NSArray *)_freshSectionInfo
{
	NSInteger numberOfSections = 1;
	
	if(_tableFlags.dataSourceNumberOfSectionsInTableView){
		numberOfSections = [_dataSource numberOfSectionsInTableView:self];
	}
	
	NSMutableArray *sections = [NSMutableArray arrayWithCapacity:numberOfSections];
	
	int s;
	CGFloat offset = [_headerView bounds].size.height - self.contentInset.top;
	for(s = 0; s < numberOfSections; ++s) {
		TUITableViewSection *section = [[TUITableViewSection alloc] initWithNumberOfRows:[_dataSource tableView:self numberOfRowsInSection:s] sectionIndex:s tableView:self];
		[section _setupRowHeights];
		section.sectionOffset = offset;
		offset += [section sectionHeight];
		[sections addObject:section];
		[section release];
	}
	
	_contentHeight = offset - self.contentInset.bottom;
	
	return sections;
}

- (void)_enqueueReusableCell:(TUITableViewCell *)cell
{
	NSString *identifier = cell.reuseIdentifier;
	
	if(!identifier)
		return;
	
	NSMutableArray *array = [_reusableTableCells objectForKey:identifier];
	if(!array) {
		array = [[NSMutableArray alloc] init];
		[_reusableTableCells setObject:array forKey:identifier];
		[array release];
	}
	[array addObject:cell];
}

- (TUITableViewCell *)dequeueReusableCellWithIdentifier:(NSString *)identifier
{
	if(!identifier)
		return nil;
	
	NSMutableArray *array = [_reusableTableCells objectForKey:identifier];
	if(array) {
		TUITableViewCell *c = [array lastObject];
		if(c) {
			[c retain];
			[array removeLastObject];
			[c prepareForReuse];
			return [c autorelease];
		}
	}
	return nil;
}

/**
 * @brief Obtain the header view for the specified section
 * 
 * If the section has no header, nil is returned.
 * 
 * @param section the section
 * @return section header
 */
- (TUIView *)headerViewForSection:(NSInteger)section {
  if(section >= 0 && section < [_sectionInfo count]){
    return [(TUITableViewSection *)[_sectionInfo objectAtIndex:section] headerView];
  }else{
    return nil;
  }
}

- (TUITableViewCell *)cellForRowAtIndexPath:(TUIFastIndexPath *)indexPath // returns nil if cell is not visible or index path is out of range
{
	return [_visibleItems objectForKey:indexPath];
}

- (NSArray *)visibleCells
{
	return [_visibleItems allValues];
}

static NSInteger SortCells(TUITableViewCell *a, TUITableViewCell *b, void *ctx)
{
	if(a.frame.origin.y > b.frame.origin.y)
		return NSOrderedAscending;
	return NSOrderedDescending;
}

- (NSArray *)sortedVisibleCells
{
	NSArray *v = [self visibleCells];
	return [v sortedArrayUsingComparator:(NSComparator)^NSComparisonResult(TUITableViewCell *a, TUITableViewCell *b) {
		if(a.frame.origin.y > b.frame.origin.y)
			return NSOrderedAscending;
		return NSOrderedDescending;
	}];
}

#define INDEX_PATHS_FOR_VISIBLE_ROWS [_visibleItems allKeys]

- (NSArray *)indexPathsForVisibleRows
{
	return INDEX_PATHS_FOR_VISIBLE_ROWS;
}

- (TUIFastIndexPath *)indexPathForCell:(TUITableViewCell *)c
{
	for(TUIFastIndexPath *i in _visibleItems) {
		TUITableViewCell *cell = [_visibleItems objectForKey:i];
		if(cell == c)
			return i;
	}
	return nil;
}

/**
 * @brief Obtain the indexes of sections which intersect @p rect.
 * 
 * @param rect the rect
 * @return intersecting sections
 */
- (NSIndexSet *)indexesOfSectionsInRect:(CGRect)rect
{
	NSMutableIndexSet *indexes = [[NSMutableIndexSet alloc] init];
	
	for(int i = 0; i < [_sectionInfo count]; i++) {
		if(CGRectIntersectsRect([self rectForSection:i], rect)){
			[indexes addIndex:i];
		}
	}
	
	return [indexes autorelease];
}

/**
 * @brief Obtain the indexes of sections whose header views intersect @p rect.
 * 
 * @param rect the rect
 * @return intersecting sections
 */
- (NSIndexSet *)indexesOfSectionHeadersInRect:(CGRect)rect
{
	NSMutableIndexSet *indexes = [[NSMutableIndexSet alloc] init];
	
	for(int i = 0; i < [_sectionInfo count]; i++) {
		if(CGRectIntersectsRect([self rectForHeaderOfSection:i], rect)){
			[indexes addIndex:i];
		}
	}
	
	return [indexes autorelease];
}

- (NSArray *)indexPathsForRowsInRect:(CGRect)rect
{
	NSMutableArray *indexPaths = [NSMutableArray arrayWithCapacity:50];
	NSInteger sectionIndex = 0;
	for(TUITableViewSection *section in _sectionInfo) {
		NSInteger numberOfRows = [section numberOfRows];
		for(NSInteger row = 0; row < numberOfRows; ++row) {
			TUIFastIndexPath *indexPath = [TUIFastIndexPath indexPathForRow:row inSection:sectionIndex];
			CGRect cellRect = [self rectForRowAtIndexPath:indexPath];
			if(CGRectIntersectsRect(cellRect, rect)) {
				[indexPaths addObject:indexPath];
			} else {
				// not visible
			}
		}
		++sectionIndex;
	}
	return indexPaths;
}

/**
 * @brief Obtain the index path of the row at the specified point
 * 
 * If the point is not valid or no row exists at that point, nil is
 * returned.
 * 
 * @param point location in the table view
 * @return index path of the row at @p point
 */
- (TUIFastIndexPath *)indexPathForRowAtPoint:(CGPoint)point {
  
	NSInteger sectionIndex = 0;
  for(TUITableViewSection *section in _sectionInfo){
    for(NSInteger row = 0; row < [section numberOfRows]; row++){
      TUIFastIndexPath *indexPath = [TUIFastIndexPath indexPathForRow:row inSection:sectionIndex];
      CGRect cellRect = [self rectForRowAtIndexPath:indexPath];
      if(CGRectContainsPoint(cellRect, point)){
        return indexPath;
      }
    }
		++sectionIndex;
  }
	
	return nil;
}

/**
 * @brief Obtain the index of a section whose header is at the specified point
 * 
 * If the point is not valid or no header exists at that point, a negative value
 * is returned.
 * 
 * @param point location in the table view
 * @return index of the section whose header is at @p point
 */
- (NSInteger)indexOfSectionWithHeaderAtPoint:(CGPoint)point {
  
	NSInteger sectionIndex = 0;
  for(TUITableViewSection *section in _sectionInfo){
    TUIView *headerView;
    if((headerView = section.headerView) != nil){
      CGFloat offset = [section sectionOffset];
      CGFloat height = [section headerHeight];
      CGFloat y = _contentHeight - offset - height;
      CGRect frame = CGRectMake(0, y, self.bounds.size.width, height);
      if(CGRectContainsPoint(frame, point)){
        return sectionIndex;
      }
    }
    sectionIndex++;
  }
	
	return -1;
}

/**
 * @brief Enumerate index paths
 * @see #enumerateIndexPathsFromIndexPath:toIndexPath:withOptions:usingBlock:
 */
- (void)enumerateIndexPathsUsingBlock:(void (^)(TUIFastIndexPath *indexPath, BOOL *stop))block {
  [self enumerateIndexPathsFromIndexPath:nil toIndexPath:nil withOptions:0 usingBlock:block];
}

/**
 * @brief Enumerate index paths
 * @see #enumerateIndexPathsFromIndexPath:toIndexPath:withOptions:usingBlock:
 */
- (void)enumerateIndexPathsWithOptions:(NSEnumerationOptions)options usingBlock:(void (^)(TUIFastIndexPath *indexPath, BOOL *stop))block {
  [self enumerateIndexPathsFromIndexPath:nil toIndexPath:nil withOptions:options usingBlock:block];
}

/**
 * @brief Enumerate index paths
 * 
 * The provided block is repeatedly invoked with each valid index path between
 * the specified bounds.  Both bounding index paths are inclusive.
 * 
 * @param fromIndexPath the index path to begin enumerating at or nil to begin at the first index path
 * @param toIndexPath the index path to stop enumerating at or nil to stop at the last index path
 * @param options enumeration options (not currently supported; pass 0)
 * @param block the block to enumerate with
 */
- (void)enumerateIndexPathsFromIndexPath:(TUIFastIndexPath *)fromIndexPath toIndexPath:(TUIFastIndexPath *)toIndexPath withOptions:(NSEnumerationOptions)options usingBlock:(void (^)(TUIFastIndexPath *indexPath, BOOL *stop))block {
  NSInteger sectionLowerBound = (fromIndexPath != nil) ? fromIndexPath.section : 0;
  NSInteger sectionUpperBound = (toIndexPath != nil) ? toIndexPath.section : [self numberOfSections] - 1;
  NSInteger rowLowerBound = (fromIndexPath != nil) ? fromIndexPath.row : 0;
  NSInteger rowUpperBound = (toIndexPath != nil) ? toIndexPath.row : -1;
  
  NSInteger irow = rowLowerBound; // start at the lower bound row for the first iteration...
  for(NSInteger i = sectionLowerBound; i < [self numberOfSections] && i <= sectionUpperBound /* inclusive */; i++){
    NSInteger rowCount = [self numberOfRowsInSection:i];
    for(NSInteger j = irow; j < rowCount && j <= ((rowUpperBound < 0 || i < sectionUpperBound) ? rowCount - 1 : rowUpperBound) /* inclusive */; j++){
      BOOL stop = FALSE;
      block([TUIFastIndexPath indexPathForRow:j inSection:i], &stop);
      if(stop) return;
    }
    irow = 0; // ...then use zero for subsequent iterations
  }
  
}

- (TUIFastIndexPath *)_topVisibleIndexPath
{
	TUIFastIndexPath *topVisibleIndex = nil;
	NSArray *v = [INDEX_PATHS_FOR_VISIBLE_ROWS sortedArrayUsingSelector:@selector(compare:)];
	if([v count])
		topVisibleIndex = [v objectAtIndex:0];
	return topVisibleIndex;
}

- (void)setFrame:(CGRect)f
{
	_tableFlags.forceSaveScrollPosition = 1;
	[super setFrame:f];
}

- (void)setContentOffset:(CGPoint)p
{
	_tableFlags.didFirstLayout = 1; // prevent the auto-scroll-to-top during the first layout
	[super setContentOffset:p];
	
	// if we're currently dragging we need to update the drag operation since the content under
	// the mouse has moved; we just call update again with the last mouse location
  if([self __isDraggingCell]){
    [self __updateDraggingCell:_dragToReorderCell offset:_currentDragToReorderMouseOffset location:_currentDragToReorderLocation];
  }
  
}

- (void)setPullDownView:(TUIView *)p
{
	[_pullDownView removeFromSuperview];
	
	[p retain];
	[_pullDownView release];
	_pullDownView = p;
	
	[self addSubview:_pullDownView];
	_pullDownView.hidden = YES;
}

- (void)setHeaderView:(TUIView *)h
{
	[_headerView removeFromSuperview];
	
	[h retain];
	[_headerView release];
	_headerView = h;
	
	[self addSubview:_headerView];
	_headerView.hidden = YES;
}

- (BOOL)_preLayoutCells
{
	CGRect bounds = self.bounds;

	if(!_sectionInfo || !CGSizeEqualToSize(bounds.size, _lastSize)) {
		// save scroll position
		CGFloat previousOffset = 0.0f;
		TUIFastIndexPath *savedIndexPath = nil;
		CGFloat relativeOffset = 0.0;
		if(_tableFlags.maintainContentOffsetAfterReload) {
			previousOffset = self.contentSize.height + self.contentOffset.y;
		} else {
			if(_tableFlags.forceSaveScrollPosition || [self.nsView inLiveResize]) {
				_tableFlags.forceSaveScrollPosition = 0;
				NSArray *a = [INDEX_PATHS_FOR_VISIBLE_ROWS sortedArrayUsingSelector:@selector(compare:)];
				if([a count]) {
					savedIndexPath = [[a objectAtIndex:0] retain];
					CGRect v = [self visibleRect];
					CGRect r = [self rectForRowAtIndexPath:savedIndexPath];
					relativeOffset = ((v.origin.y + v.size.height) - (r.origin.y + r.size.height));
					relativeOffset += (_lastSize.height - bounds.size.height);
				}
			} else if(_keepVisibleIndexPathForReload) {
				savedIndexPath = [_keepVisibleIndexPathForReload retain];
				relativeOffset = _relativeOffsetForReload;
				[_keepVisibleIndexPathForReload release];
				_keepVisibleIndexPathForReload = nil;
			}
		}
		
		
		[_sectionInfo release];
		_sectionInfo = [[self _freshSectionInfo] retain]; // calculates new contentHeight here
		self.contentSize = CGSizeMake(self.bounds.size.width, _contentHeight);
		
		_lastSize = bounds.size;
		
		if(!_tableFlags.didFirstLayout) {
			_tableFlags.didFirstLayout = 1;
			[self scrollToTopAnimated:NO];
		}
		
		// restore scroll position
		if(_tableFlags.maintainContentOffsetAfterReload) {
			CGFloat newOffset = previousOffset - self.contentSize.height;
			self.contentOffset = CGPointMake(self.contentOffset.x, newOffset);
		} else {
			if(savedIndexPath) {
				CGRect v = [self visibleRect];
				CGRect r = [self rectForRowAtIndexPath:savedIndexPath];
				r.origin.y -= (v.size.height - r.size.height);
				r.size.height += (v.size.height - r.size.height);
				
				r.origin.y += relativeOffset;
				
				[self scrollRectToVisible:r animated:NO];
				[savedIndexPath release];
			}
		}
		
		return YES; // needs visible cells to be redisplayed
	}
	
	return NO; // just need to do the recycling
}

/**
 * @brief Layout header views for sections which have one.
 */
- (void)_layoutSectionHeaders:(BOOL)visibleHeadersNeedRelayout
{
	if(visibleHeadersNeedRelayout) {
		if(_visibleSectionHeaders != nil){
			[_visibleSectionHeaders enumerateIndexesUsingBlock:^(NSUInteger index, BOOL *stop) {
				if(index < [_sectionInfo count]) {
					TUITableViewSection *section = [_sectionInfo objectAtIndex:index];
					if(section.headerView != nil) {
						section.headerView.frame = [self rectForHeaderOfSection:index];
						[section.headerView setNeedsLayout];
					}
				}
			}];
		}
	}
  
	CGRect visible = [self visibleRect];
	
	NSIndexSet *oldIndexes = _visibleSectionHeaders;
	NSIndexSet *newIndexes = [self indexesOfSectionHeadersInRect:visible];
	
	NSMutableIndexSet *toRemove = [[oldIndexes mutableCopy] autorelease];
	[toRemove removeIndexes:newIndexes];
	NSMutableIndexSet *toAdd = [[newIndexes mutableCopy] autorelease];
	[toAdd removeIndexes:oldIndexes];
	
	// remove offscreen headers
	[toRemove enumerateIndexesUsingBlock:^(NSUInteger index, BOOL *stop) {
		if(index < [_sectionInfo count]) {
			TUITableViewSection *section = [_sectionInfo objectAtIndex:index];
			if(section.headerView != nil) {
				[section.headerView removeFromSuperview];
			}
		}
		[_visibleSectionHeaders removeIndex:index];
	}];
	
	// add new headers
	[toAdd enumerateIndexesUsingBlock:^(NSUInteger index, BOOL *stop) {
		if(index < [_sectionInfo count]){
			TUITableViewSection *section = [_sectionInfo objectAtIndex:index];
			if(section.headerView != nil) {
				section.headerView.frame = [self rectForHeaderOfSection:index];
				[section.headerView setNeedsLayout];
				[self addSubview:section.headerView];
			}
		}
		[_visibleSectionHeaders addIndex:index];
	}];
}

- (void)_layoutCells:(BOOL)visibleCellsNeedRelayout
{
  
	if(visibleCellsNeedRelayout) {
		// update remaining visible cells if needed
		for(TUIFastIndexPath *i in _visibleItems) {
			TUITableViewCell *cell = [_visibleItems objectForKey:i];
			cell.frame = [self rectForRowAtIndexPath:i];
			[cell setNeedsLayout];
		}
	}
	
	CGRect visible = [self visibleRect];
	
	// Example:
	// old:            0 1 2 3 4 5 6 7
	// new:                2 3 4 5 6 7 8 9
	// to remove:      0 1
	// to add:                         8 9
	
	NSArray *oldVisibleIndexPaths = INDEX_PATHS_FOR_VISIBLE_ROWS;
	NSArray *newVisibleIndexPaths = [self indexPathsForRowsInRect:visible];
	
	NSMutableArray *indexPathsToRemove = [[oldVisibleIndexPaths mutableCopy] autorelease];
	[indexPathsToRemove removeObjectsInArray:newVisibleIndexPaths];
	
	NSMutableArray *indexPathsToAdd = [[newVisibleIndexPaths mutableCopy] autorelease];
	[indexPathsToAdd removeObjectsInArray:oldVisibleIndexPaths];
	
	// remove offscreen cells
	for(TUIFastIndexPath *i in indexPathsToRemove) {
		TUITableViewCell *cell = [self cellForRowAtIndexPath:i];
		// don't reuse the dragged cell
		if(_dragToReorderCell == nil || ![cell isEqual:_dragToReorderCell]){
      [self _enqueueReusableCell:cell];
      [cell removeFromSuperview];
      [_visibleItems removeObjectForKey:i];
    }
	}
	
	// add new cells
	for(TUIFastIndexPath *i in indexPathsToAdd) {
		if([_visibleItems objectForKey:i]) {
			NSLog(@"!!! Warning: already have a cell in place for index path %@\n\n\n", i);
		} else {
			TUITableViewCell *cell = [_dataSource tableView:self cellForRowAtIndexPath:i];
			[self.nsView invalidateHoverForView:cell];
			cell.frame = [self rectForRowAtIndexPath:i];
			[cell setNeedsLayout];
			[cell prepareForDisplay];
			if([i isEqual:_selectedIndexPath]) {
				[cell setSelected:YES animated:NO];
			} else {
				[cell setSelected:NO animated:NO];
			}
			
			[self addSubview:cell];
			
			if([_indexPathShouldBeFirstResponder isEqual:i]) {
			  // only make cells first responder if they accept it
			  if([cell acceptsFirstResponder]){
			    [self.nsWindow makeFirstResponderIfNotAlreadyInResponderChain:cell withFutureRequestToken:_futureMakeFirstResponderToken];
			  }
				[_indexPathShouldBeFirstResponder release];
				_indexPathShouldBeFirstResponder = nil;
			}
			
			[_visibleItems setObject:cell forKey:i];
		}
	}
	
  // if we have a dragged cell, make sure it's on top of the newly added cells
  if([indexPathsToAdd count] > 0 && _dragToReorderCell != nil){
    [[_dragToReorderCell superview] bringSubviewToFront:_dragToReorderCell];
  }
  
	if(_headerView) {
		CGSize s = self.contentSize;
		CGRect headerViewRect = CGRectMake(0, s.height - _headerView.frame.size.height, visible.size.width, _headerView.frame.size.height);
		if(CGRectIntersectsRect(headerViewRect, visible)) {
			_headerView.frame = headerViewRect;
			
			if(_headerView.hidden) {
				// show
				_headerView.hidden = NO;
			}
		} else {
			if(!_headerView.hidden) {
				_headerView.hidden = YES;
			}
		}
	}
	
	if(_pullDownView) {
		CGSize s = self.contentSize;
		CGRect pullDownRect = CGRectMake(0, s.height, visible.size.width, _pullDownView.frame.size.height);
		if([self pullDownViewIsVisible]) {
			if(_pullDownView.hidden) {
				// show
				_pullDownView.frame = pullDownRect;
				_pullDownView.hidden = NO;
			}
		} else {
			if(!_pullDownView.hidden) {
				_pullDownView.hidden = YES;
			}
		}
	}
}

- (BOOL)pullDownViewIsVisible
{
	if(_pullDownView) {
		CGSize s = self.contentSize;
		CGRect visible = [self visibleRect];
		CGRect pullDownRect = CGRectMake(0, s.height, visible.size.width, _pullDownView.frame.size.height);
		return CGRectIntersectsRect(pullDownRect, visible);
	}
	return NO;
}

- (void)reloadDataMaintainingVisibleIndexPath:(TUIFastIndexPath *)indexPath relativeOffset:(CGFloat)relativeOffset
{
	[_keepVisibleIndexPathForReload release];
	_keepVisibleIndexPathForReload = [indexPath retain];
	_relativeOffsetForReload = relativeOffset;
	[self reloadData];
}

- (void)reloadData
{
  
  // notify our delegate we're about to reload the table
  if(self.delegate != nil && [self.delegate respondsToSelector:@selector(tableViewWillReloadData:)]){
    [self.delegate tableViewWillReloadData:self];
  }
  
	// need to recycle all visible cells, have them be regenerated on layoutSubviews
	// because the same cells might have different content
	for(TUIFastIndexPath *i in _visibleItems) {
		TUITableViewCell *cell = [_visibleItems objectForKey:i];
		[self _enqueueReusableCell:cell];
		[cell removeFromSuperview];
	}
	
	// if we have a dragged cell, clear it
	[_dragToReorderCell release];
	_dragToReorderCell = nil;
	
	// clear visible cells
	[_visibleItems removeAllObjects];
	
	// remove any visible headers, they should be re-added when the table is laid out
	for(TUITableViewSection *section in _sectionInfo){
	  TUIView *headerView;
	  if((headerView = [section headerView]) != nil){
	    [headerView removeFromSuperview];
	  }
	}
	
	// clear visible section headers
	[_visibleSectionHeaders removeAllIndexes];
	
	[_sectionInfo release];
	_sectionInfo = nil; // will be regenerated on next layout
	
	[self layoutSubviews];
	
  // notify our delegate the table view has been reloaded
  if(self.delegate != nil && [self.delegate respondsToSelector:@selector(tableViewDidReloadData:)]){
    [self.delegate tableViewDidReloadData:self];
  }
  
}

- (void)layoutSubviews
{
	if(!_tableFlags.layoutSubviewsReentrancyGuard) {
		_tableFlags.layoutSubviewsReentrancyGuard = 1;
		
		[TUIView setAnimationsEnabled:NO block:^{
			[CATransaction begin];
			[CATransaction setDisableActions:YES];
			
			BOOL visibleCellsNeedRelayout = [self _preLayoutCells];
			[super layoutSubviews]; // this will munge with the contentOffset
			[self _layoutSectionHeaders:visibleCellsNeedRelayout];
			[self _layoutCells:visibleCellsNeedRelayout];
			
			if(_tableFlags.derepeaterEnabled)
				[self _updateDerepeaterViews];
			
			[CATransaction commit];
		}];
		
		_tableFlags.layoutSubviewsReentrancyGuard = 0;
	} else {
//		NSLog(@"trying to nest...");
	}
}

- (void)scrollToRowAtIndexPath:(TUIFastIndexPath *)indexPath atScrollPosition:(TUITableViewScrollPosition)scrollPosition animated:(BOOL)animated
{
	CGRect v = [self visibleRect];
	CGRect r = [self rectForRowAtIndexPath:indexPath];
	switch(scrollPosition) {
		case TUITableViewScrollPositionNone:
			// do nothing
			break;
		case TUITableViewScrollPositionTop:
			r.origin.y -= (v.size.height - r.size.height);
			r.size.height += (v.size.height - r.size.height);
			[self scrollRectToVisible:r animated:animated];
			break;
		case TUITableViewScrollPositionToVisible:
		default:
			[self scrollRectToVisible:r animated:animated];
			break;
		
	}
}

- (TUIFastIndexPath *)indexPathForSelectedRow
{
	return _selectedIndexPath;
}

- (TUIFastIndexPath *)indexPathForFirstRow
{
	return [TUIFastIndexPath indexPathForRow:0 inSection:0];
}

- (TUIFastIndexPath *)indexPathForLastRow
{
	NSInteger sec = [self numberOfSections] - 1;
	NSInteger row = [self numberOfRowsInSection:sec] - 1;
	return [TUIFastIndexPath indexPathForRow:row inSection:sec];
}

- (void)_makeRowAtIndexPathFirstResponder:(TUIFastIndexPath *)indexPath
{
	TUITableViewCell *cell = [self cellForRowAtIndexPath:indexPath];
	// only cells that accept first responder should be made first responder
	if(cell && [cell acceptsFirstResponder]) {
		[self.nsWindow makeFirstResponderIfNotAlreadyInResponderChain:cell];
	} else {
		[_indexPathShouldBeFirstResponder release];
		_indexPathShouldBeFirstResponder = [indexPath retain];
		_futureMakeFirstResponderToken = [self.nsWindow futureMakeFirstResponderRequestToken];
	}
}

- (void)selectRowAtIndexPath:(TUIFastIndexPath *)indexPath animated:(BOOL)animated scrollPosition:(TUITableViewScrollPosition)scrollPosition
{
  
	if([indexPath isEqual:[self indexPathForSelectedRow]]) {
		// just scroll to visible
	} else {
		[self deselectRowAtIndexPath:[self indexPathForSelectedRow] animated:animated];
		
		TUITableViewCell *cell = [self cellForRowAtIndexPath:indexPath]; // may be nil
		[cell setSelected:YES animated:animated];
		[_selectedIndexPath release]; // should already be nil
		_selectedIndexPath = [indexPath retain];
		[cell setNeedsDisplay];
		
		// only notify when the selection actually changes
    if([self.delegate respondsToSelector:@selector(tableView:didSelectRowAtIndexPath:)]){
      [self.delegate tableView:self didSelectRowAtIndexPath:indexPath];
    }
		
	}
	
	[self _makeRowAtIndexPathFirstResponder:indexPath];
	[self scrollToRowAtIndexPath:indexPath atScrollPosition:scrollPosition animated:animated];
}

- (void)deselectRowAtIndexPath:(TUIFastIndexPath *)indexPath animated:(BOOL)animated
{
  
	if([indexPath isEqual:_selectedIndexPath]) {
		TUITableViewCell *cell = [self cellForRowAtIndexPath:indexPath]; // may be nil
		
		[cell setSelected:NO animated:animated];
		[_selectedIndexPath release];
		_selectedIndexPath = nil;
		[cell setNeedsDisplay];
		
		// only notify when the selection actually changes
    if([self.delegate respondsToSelector:@selector(tableView:didDeselectRowAtIndexPath:)]){
      [self.delegate tableView:self didDeselectRowAtIndexPath:indexPath];
    }
    
	}
	
}

- (TUIFastIndexPath *)indexPathForFirstVisibleRow 
{
	TUIFastIndexPath *firstIndexPath = nil;
	for(TUIFastIndexPath *indexPath in _visibleItems) {
		if(firstIndexPath == nil || [indexPath compare:firstIndexPath] == NSOrderedAscending) {
			firstIndexPath = indexPath;
		}
	}
	return firstIndexPath;
}

- (TUIFastIndexPath *)indexPathForLastVisibleRow 
{
	TUIFastIndexPath *lastIndexPath = nil;
	for(TUIFastIndexPath *indexPath in _visibleItems) {
		if(lastIndexPath == nil || [indexPath compare:lastIndexPath] == NSOrderedDescending) {
			lastIndexPath = indexPath;
		}
	}
	return lastIndexPath;
}

- (BOOL)performKeyAction:(NSEvent *)event
{
	// no selection or selected cell not visible and this is not repeative key press
	BOOL noCurrentSelection = (_selectedIndexPath == nil || ([self cellForRowAtIndexPath:_selectedIndexPath] == nil && ![event isARepeat]));;
	
	switch([[event charactersIgnoringModifiers] characterAtIndex:0]) {
		case NSUpArrowFunctionKey: {
			TUIFastIndexPath *newIndexPath;
			if(noCurrentSelection) {
				newIndexPath = [self indexPathForLastVisibleRow];
			} else {
				NSUInteger section = _selectedIndexPath.section;
				NSUInteger row = _selectedIndexPath.row;
				if(row > 0) {
					row--;
				} else {
					while(section > 0) {
						section--;
						NSUInteger rowsInSection = [self numberOfRowsInSection:section];
						if(rowsInSection > 0) {
							row = rowsInSection - 1;
							break;
						}
					}
				}
				newIndexPath = [TUIFastIndexPath indexPathForRow:row inSection:section];
			}
			if(![_delegate respondsToSelector:@selector(tableView:shouldSelectRowAtIndexPath:forEvent:)] || [_delegate tableView:self shouldSelectRowAtIndexPath:newIndexPath forEvent:event]){
				[self selectRowAtIndexPath:newIndexPath animated:self.animateSelectionChanges scrollPosition:TUITableViewScrollPositionToVisible];
			}

			return YES;
		}
	
		case NSDownArrowFunctionKey:  {
			TUIFastIndexPath *newIndexPath;
			if(noCurrentSelection) {
				newIndexPath = [self indexPathForFirstVisibleRow]; 
			} else {
				NSUInteger section = _selectedIndexPath.section;
				NSUInteger row = _selectedIndexPath.row;
				NSUInteger rowsInSection = [self numberOfRowsInSection:section];
				if(row + 1 < rowsInSection) {
					row++;
				} else {
					NSUInteger sections = [self numberOfSections];
					while(section + 1 < sections) {
						section++;
						NSUInteger rowsInSection = [self numberOfRowsInSection:section];
						if(rowsInSection > 0) {
							row = 0;
							break;
						}
					}
				}
				newIndexPath = [TUIFastIndexPath indexPathForRow:row inSection:section];
			}
			
			if(![_delegate respondsToSelector:@selector(tableView:shouldSelectRowAtIndexPath:forEvent:)] || [_delegate tableView:self shouldSelectRowAtIndexPath:newIndexPath forEvent:event]){
				[self selectRowAtIndexPath:newIndexPath animated:self.animateSelectionChanges scrollPosition:TUITableViewScrollPositionToVisible];
			}
			
			return YES;
		}
	}
	
	return [super performKeyAction:event];
}

- (BOOL)maintainContentOffsetAfterReload
{
	return _tableFlags.maintainContentOffsetAfterReload;
}

- (void)setMaintainContentOffsetAfterReload:(BOOL)newValue
{
	_tableFlags.maintainContentOffsetAfterReload = newValue;
}

@end


@implementation NSIndexPath (TUITableView)

+ (NSIndexPath *)indexPathForRow:(NSUInteger)row inSection:(NSUInteger)section
{
	NSUInteger i[] = {section, row};
	return [NSIndexPath indexPathWithIndexes:i length:2];
}

- (NSUInteger)section
{
	return [self indexAtPosition:0];
}

- (NSUInteger)row
{
	return [self indexAtPosition:1];
}

@end