/*

     File: AppListViewController.m 

 Abstract: Controller for the main table view of the TopPaid 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: 1.1 

 Disclaimer: IMPORTANT:  This Apple software is supplied to you by Apple 

 Inc. ("Apple") in consideration of your agreement to the following 

 terms, and your use, installation, modification or redistribution of 

 this Apple software constitutes acceptance of these terms.  If you do 

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 redistribute this Apple software. 

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 subject to these terms, Apple grants you a personal, non-exclusive 

 license, under Apple's copyrights in this original Apple software (the 

 "Apple Software"), to use, reproduce, modify and redistribute the Apple 

 Software, with or without modifications, in source and/or binary forms; 

 provided that if you redistribute the Apple Software in its entirety and 

 without modifications, you must retain this notice and the following 

 text and disclaimers in all such redistributions of the Apple Software. 

 Neither the name, trademarks, service marks or logos of Apple Inc. may 

 be used to endorse or promote products derived from the Apple Software 

 without specific prior written permission from Apple.  Except as 

 expressly stated in this notice, no other rights or licenses, express or 

 implied, are granted by Apple herein, including but not limited to any 

 patent rights that may be infringed by your derivative works or by other 

 works in which the Apple Software may be incorporated. 

 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 

 INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION, 

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 Copyright (C) 2011 Apple Inc. All Rights Reserved. 

 */

#import "AppDelegate.h"

#import "AppListViewController.h"

#import "AppRecord.h"

#import "ContentController.h"

#define kCustomRowHeight    60.0

#define kCustomRowCount     7

#pragma mark -

@interface AppListViewController ()

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

@end

@implementation AppListViewController

@synthesize entries;

@synthesize imageDownloadsInProgress;

@synthesize contentController;

#pragma mark -

#pragma mark UIViewController

- (void)viewDidLoad

{

    [super viewDidLoad];

    self.imageDownloadsInProgress = [NSMutableDictionary dictionary];

    self.tableView.rowHeight = kCustomRowHeight;

    // start listening for download completion

    [[NSNotificationCenter defaultCenter] addObserver:self

                                             selector:@selector(downloadCompleted:)

                                                 name:AppDataDownloadCompleted

                                               object:nil];

}

- (void)viewDidUnload

{

    [super viewDidUnload];

    // no longer wanting to listen for download completion

    [[NSNotificationCenter defaultCenter] removeObserver:self

                                                    name:AppDataDownloadCompleted

                                                  object:nil];

}

- (void)dealloc

{

    [entries release];

    [imageDownloadsInProgress release];

    [contentController release];

    [super dealloc];

}

- (void)didReceiveMemoryWarning

{

    [super didReceiveMemoryWarning];

    // terminate all pending download connections

    NSArray *allDownloads = [self.imageDownloadsInProgress allValues];

    [allDownloads performSelector:@selector(cancelDownload)];

}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation

{

    return YES;

}

#pragma mark -

#pragma mark Table view creation (UITableViewDataSource)

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath

{

    if (entries != nil && entries.count > 0)

    {

        AppRecord *app = [entries objectAtIndex:indexPath.row];

        contentController.detailItem = app;

    }

}

// customize the number of rows in the table view

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section

{

    int count = [entries count];

    // if 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 = @"TableCell";

    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];

    }

    // 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;

        }

        cell.accessoryType = UITableViewCellAccessoryNone;

    }

    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;

    }

}

#pragma mark -

#pragma mark Deferred image loading (UIScrollViewDelegate)

- (void)downloadCompleted:(NSNotification *)notification

{

    self.entries = [notification object];   // incoming object is an NSArray of AppRecords

    [self.tableView reloadData];

}

// 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