/*
     File: RootViewController.m 
 Abstract: Controller for the main table view of the LazyTable sample.
    This table view controller works off the AppDelege's data model.
    produce a three-stage lazy load:
    1. No data (i.e. an empty table)
    2. Text-only data from the model's RSS feed
    3. Images loaded over the network asynchronously
 
    This process allows for asynchronous loading of the table to keep the UI responsive.
    Stage 3 is managed by the AppRecord corresponding to each row/cell.
 
    Images are scaled to the desired height.
    If rapid scrolling is in progress, downloads do not begin until scrolling has ended.
  
  Version: 1.3 
  
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 without specific prior written permission from Apple.  Except as 
 expressly stated in this notice, no other rights or licenses, express or 
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 The Apple Software is provided by Apple on an "AS IS" basis.  APPLE 
 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION 
 THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS 
 FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND 
 OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS. 
  
 IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL 
 OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
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 */

#import "RootViewController.h"
#import "AppRecord.h"

#define kCustomRowHeight    60.0
#define kCustomRowCount     7

#pragma mark -

@interface RootViewController ()

- (void)startIconDownload:(AppRecord *)appRecord forIndexPath:(NSIndexPath *)indexPath;

@end

@implementation RootViewController

@synthesize entries;
@synthesize imageDownloadsInProgress;


#pragma mark 

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    self.imageDownloadsInProgress = [NSMutableDictionary dictionary];
    self.tableView.rowHeight = kCustomRowHeight;
}

- (void)dealloc
{
    [entries release];
	[imageDownloadsInProgress release];
    
    [super dealloc];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    
    // terminate all pending download connections
    NSArray *allDownloads = [self.imageDownloadsInProgress allValues];
    [allDownloads makeObjectsPerformSelector:@selector(cancelDownload)];
}

#pragma mark -
#pragma mark Table view creation (UITableViewDataSource)

// customize the number of rows in the table view
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
	int count = [entries count];
	
	// ff there's no data yet, return enough rows to fill the screen
    if (count == 0)
	{
        return kCustomRowCount;
    }
    return count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
	// customize the appearance of table view cells
	//
	static NSString *CellIdentifier = @"LazyTableCell";
    static NSString *PlaceholderCellIdentifier = @"PlaceholderCell";
    
    // add a placeholder cell while waiting on table data
    int nodeCount = [self.entries count];
	
	if (nodeCount == 0 && indexPath.row == 0)
	{
        UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:PlaceholderCellIdentifier];
        if (cell == nil)
		{
            cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
										   reuseIdentifier:PlaceholderCellIdentifier] autorelease];   
            cell.detailTextLabel.textAlignment = UITextAlignmentCenter;
			cell.selectionStyle = UITableViewCellSelectionStyleNone;
        }

		cell.detailTextLabel.text = @"Loading…";
		
		return cell;
    }
	
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil)
	{
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
									   reuseIdentifier:CellIdentifier] autorelease];
		cell.selectionStyle = UITableViewCellSelectionStyleNone;
    }

    // Leave cells empty if there's no data yet
    if (nodeCount > 0)
	{
        // Set up the cell...
        AppRecord *appRecord = [self.entries objectAtIndex:indexPath.row];
        
		cell.textLabel.text = appRecord.appName;
        cell.detailTextLabel.text = appRecord.artist;
		
        // Only load cached images; defer new downloads until scrolling ends
        if (!appRecord.appIcon)
        {
            if (self.tableView.dragging == NO && self.tableView.decelerating == NO)
            {
                [self startIconDownload:appRecord forIndexPath:indexPath];
            }
            // if a download is deferred or in progress, return a placeholder image
            cell.imageView.image = [UIImage imageNamed:@"Placeholder.png"];                
        }
        else
        {
           cell.imageView.image = appRecord.appIcon;
        }

    }
    
    return cell;
}


#pragma mark -
#pragma mark Table cell image support

- (void)startIconDownload:(AppRecord *)appRecord forIndexPath:(NSIndexPath *)indexPath
{
    IconDownloader *iconDownloader = [imageDownloadsInProgress objectForKey:indexPath];
    if (iconDownloader == nil) 
    {
        iconDownloader = [[IconDownloader alloc] init];
        iconDownloader.appRecord = appRecord;
        iconDownloader.indexPathInTableView = indexPath;
        iconDownloader.delegate = self;
        [imageDownloadsInProgress setObject:iconDownloader forKey:indexPath];
        [iconDownloader startDownload];
        [iconDownloader release];   
    }
}

// this method is used in case the user scrolled into a set of cells that don't have their app icons yet
- (void)loadImagesForOnscreenRows
{
    if ([self.entries count] > 0)
    {
        NSArray *visiblePaths = [self.tableView indexPathsForVisibleRows];
        for (NSIndexPath *indexPath in visiblePaths)
        {
            AppRecord *appRecord = [self.entries objectAtIndex:indexPath.row];
            
            if (!appRecord.appIcon) // avoid the app icon download if the app already has an icon
            {
                [self startIconDownload:appRecord forIndexPath:indexPath];
            }
        }
    }
}

// called by our ImageDownloader when an icon is ready to be displayed
- (void)appImageDidLoad:(NSIndexPath *)indexPath
{
    IconDownloader *iconDownloader = [imageDownloadsInProgress objectForKey:indexPath];
    if (iconDownloader != nil)
    {
        UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:iconDownloader.indexPathInTableView];
        
        // Display the newly loaded image
        cell.imageView.image = iconDownloader.appRecord.appIcon;
    }
    
    // Remove the IconDownloader from the in progress list.
    // This will result in it being deallocated.
    [imageDownloadsInProgress removeObjectForKey:indexPath];
}


#pragma mark -
#pragma mark Deferred image loading (UIScrollViewDelegate)

// Load images for all onscreen rows when scrolling is finished
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
    if (!decelerate)
	{
        [self loadImagesForOnscreenRows];
    }
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    [self loadImagesForOnscreenRows];
}

@end