/*

     File: AssetBrowserController.m

 Abstract: UIViewController allowing asset selection.

  Version: 1.3

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 */

#import "AssetBrowserController.h"

#import "AssetBrowserSource.h"

#import <AVFoundation/AVFoundation.h>

#import <CoreMedia/CoreMedia.h>

#import <MobileCoreServices/UTCoreTypes.h>

/* Generating thumbnails is expensive and requires a lot of resources.

 If we do this while scrolling our framerate is affected. If your app presents a persistent

 media library it may make sense to cache thumbnails and metadata in a database. */

#define ONLY_GENERATE_THUMBS_AND_TITLES_WHEN_NOT_SCROLLING 1

@interface AssetBrowserController () <AssetBrowserSourceDelegate, UIScrollViewDelegate, UITableViewDelegate, UITableViewDataSource>

@property (nonatomic, copy) NSArray *assetSources;

- (void)configureCell:(UITableViewCell*)cell forIndexPath:(NSIndexPath *)indexPath;

- (void)updateActiveAssetSources;

- (void)enableThumbnailAndTitleGeneration;

- (void)disableThumbnailAndTitleGeneration;

- (void)generateThumbnailsAndTitles;

- (void)cancelAction;

@end

@implementation AssetBrowserController

@synthesize assetSources;

@synthesize delegate;

enum {

    AssetBrowserScrollDirectionDown,

    AssetBrowserScrollDirectionUp

};

#pragma mark -

#pragma mark Initialization

- (id)initWithSourceType:(AssetBrowserSourceType)sourceType modalPresentation:(BOOL)modalPresentation;

{

    if ((self = [super initWithStyle:UITableViewStylePlain])) 

    {

        browserSourceType = sourceType;

        if ((browserSourceType & AssetBrowserSourceTypeAll) == 0) {

            NSLog(@"AssetBrowserController: Invalid sourceType");

            return nil;

        }

        [self setEdgesForExtendedLayout:UIRectEdgeAll];

        thumbnailScale = [[UIScreen mainScreen] scale];

        activeAssetSources = [[NSMutableArray alloc] initWithCapacity:0];

        isModal = modalPresentation;

        // Okay now generate the list of Assets to be displayed.

        // This should be relatively quick since we are not creating assets or thumbnails.

        NSMutableArray *sources = [NSMutableArray arrayWithCapacity:0];

        if (browserSourceType & AssetBrowserSourceTypeFileSharing) {

            [sources addObject:[AssetBrowserSource assetBrowserSourceOfType:AssetBrowserSourceTypeFileSharing]];

        }

        if (browserSourceType & AssetBrowserSourceTypeCameraRoll) {

            [sources addObject:[AssetBrowserSource assetBrowserSourceOfType:AssetBrowserSourceTypeCameraRoll]];

        }

        if (browserSourceType & AssetBrowserSourceTypeIPodLibrary) {

            [sources addObject:[AssetBrowserSource assetBrowserSourceOfType:AssetBrowserSourceTypeIPodLibrary]];

        }

        self.assetSources = sources;

        if ([sources count] == 1) {

            singleSourceTypeMode = YES;

            self.title = [[self.assetSources objectAtIndex:0] name];

        }

        else {

            self.title = NSLocalizedString(@"Media", nil);

        }

    }

    return self;

}

#pragma mark -

#pragma mark View lifecycle

- (void)viewDidLoad

{

    [super viewDidLoad];

    self.tableView.rowHeight = 65.0; // 1 point is for the divider, we want our thumbnails to have an even height.

    if (!singleSourceTypeMode)

        self.tableView.sectionHeaderHeight = 22.0;

    // We wait until the scroll view has finished decelerating to generate thumbnails so make the deceleration a bit faster than normal.

    float decel = UIScrollViewDecelerationRateNormal - (UIScrollViewDecelerationRateNormal - UIScrollViewDecelerationRateFast)/2.0;

    self.tableView.decelerationRate = decel;    

    if (isModal && (self.modalPresentationStyle == UIModalPresentationFullScreen)) {

        self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCancel 

                                                                                                target:self action:@selector(cancelAction)];

    }

}

- (void)viewWillAppear:(BOOL)animated

{   

    [super viewWillAppear:animated];

    if (isModal && (self.modalPresentationStyle == UIModalPresentationFullScreen)) {

        lastStatusBarStyle = [UIApplication sharedApplication].statusBarStyle;

        if ( lastStatusBarStyle != UIStatusBarStyleLightContent ) {

            [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent animated:animated];

        }

    }

    lastTableViewYContentOffset = self.tableView.contentOffset.y;

    lastTableViewScrollDirection = AssetBrowserScrollDirectionDown;

    if (haveBuiltSourceLibraries)

        return;

    haveBuiltSourceLibraries = YES;

    for (AssetBrowserSource *source in self.assetSources) {

        [source buildSourceLibrary];

    }

    [self updateActiveAssetSources];

    [self.tableView reloadData];

    for (AssetBrowserSource *source in self.assetSources) {

        source.delegate = self; 

    }

}

- (void)cancelAction

{

    if ([self.delegate respondsToSelector:@selector(assetBrowserDidCancel:)]) {

        [self.delegate assetBrowserDidCancel:self];

    }

}

- (void)viewDidAppear:(BOOL)animated

{

    [super viewDidAppear:animated];

    [self enableThumbnailAndTitleGeneration];

    [self generateThumbnailsAndTitles];

    NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];

    if (indexPath) {

        [self.tableView deselectRowAtIndexPath:indexPath animated:YES];

    }

}

- (void)viewWillDisappear:(BOOL)animated {

    [super viewWillDisappear:animated];

    [self disableThumbnailAndTitleGeneration];

    if (isModal && (self.modalPresentationStyle == UIModalPresentationFullScreen)) {

        if ( lastStatusBarStyle != UIStatusBarStyleLightContent ) {

            [[UIApplication sharedApplication] setStatusBarStyle:lastStatusBarStyle animated:animated];

        }

    }

}

- (void)viewDidDisappear:(BOOL)animated {

    [super viewDidDisappear:animated];

    NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];

    if (indexPath)

        [self.tableView deselectRowAtIndexPath:indexPath animated:NO];

}

- (void)clearSelection

{

    NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];

    if (indexPath)

        [self.tableView deselectRowAtIndexPath:indexPath animated:YES]; 

}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation

{

    if ( [UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad ) {

        return YES;

    }

    return (interfaceOrientation == UIInterfaceOrientationPortrait);

}

- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation

{

    // If a thumbnail finished while we were rotating then its cell might not have been updated, but the cell could still be cached.

    for (UITableViewCell *visibleCell in [self.tableView visibleCells]) {

        NSIndexPath *indexPath = [self.tableView indexPathForCell:visibleCell];

        [self configureCell:visibleCell forIndexPath:indexPath];

    }

}

#pragma mark -

#pragma mark Table view data source

- (void)updateActiveAssetSources

{

    [activeAssetSources removeAllObjects];

    for (AssetBrowserSource *source in self.assetSources) {

        if ( ([source.items count] > 0) ) {

            [activeAssetSources addObject:source];

        }

    }

}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView 

{

    return [activeAssetSources count];

}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section 

{

    if (singleSourceTypeMode)

        return nil;

    AssetBrowserSource *source = [activeAssetSources objectAtIndex:section];

    NSString *name = [source.items count] > 0 ? source.name : nil;

    return name;

}

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

    NSInteger numRows = 0;

    numRows = [[[activeAssetSources objectAtIndex:section] items] count];

    return numRows;

}

- (void)configureCell:(UITableViewCell*)cell forIndexPath:(NSIndexPath *)indexPath

{   

    if ( cell == nil)

        return;

    AssetBrowserSource *source = [activeAssetSources objectAtIndex:indexPath.section];

    AssetBrowserItem *item = [[source items] objectAtIndex:indexPath.row];

    cell.textLabel.text = item.title;

    UIImage *thumb = item.thumbnailImage;

    if ( !thumb || !item.haveRichestTitle ) {

        [self generateThumbnailsAndTitles];

    }

    if (!thumb) {

        thumb = [item placeHolderImage];

    }

    cell.imageView.image = thumb;

}

// Customize the appearance of table view cells.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 

{    

    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    if (cell == nil) {

        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];

        cell.textLabel.font = [UIFont boldSystemFontOfSize:14.0];

        cell.accessoryType = isModal ? UITableViewCellAccessoryNone : UITableViewCellAccessoryDisclosureIndicator;

    }

    [self configureCell:cell forIndexPath:indexPath];

    return cell;

}

#pragma mark -

#pragma mark Table view delegate

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

{       

    AssetBrowserItem *selectedItem = [[(AssetBrowserSource*)[activeAssetSources objectAtIndex:indexPath.section] items] objectAtIndex:indexPath.row];

    if ([self.delegate respondsToSelector:@selector(assetBrowser:didChooseItem:)]) {

        AssetBrowserItem *selectedItemCopy = [selectedItem copy];

        [self.delegate assetBrowser:self didChooseItem:selectedItemCopy];

    }

}

#pragma mark -

#pragma mark Asset Library Delegate

- (void)assetBrowserSourceItemsDidChange:(AssetBrowserSource*)source

{   

    [self updateActiveAssetSources];

    [self.tableView reloadData];

}

#pragma mark -

#pragma mark Thumbnail Generation

- (void)updateCellForBrowserItemIfVisible:(AssetBrowserItem*)browserItem

{

    NSArray *visibleIndexPaths = [self.tableView indexPathsForVisibleRows];

    for (NSIndexPath *indexPath in visibleIndexPaths) {

        AssetBrowserItem *visibleBrowserItem = [[[activeAssetSources objectAtIndex:indexPath.section] items] objectAtIndex:indexPath.row];

        if ([browserItem isEqual:visibleBrowserItem]) {

            UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:indexPath];

            [self configureCell:cell forIndexPath:indexPath];

            [cell setNeedsLayout];

            break;

        }

    }

}

- (void)thumbnailsAndTitlesTask

{   

    if (! thumbnailAndTitleGenerationEnabled) {

        thumbnailAndTitleGenerationIsRunning = NO;

        return;

    }

    thumbnailAndTitleGenerationIsRunning = YES;

    NSArray *visibleIndexPaths = [self.tableView indexPathsForVisibleRows];

    id objOrEnumerator = (lastTableViewScrollDirection == AssetBrowserScrollDirectionDown) ? (id)visibleIndexPaths : (id)[visibleIndexPaths reverseObjectEnumerator];

    for (NSIndexPath *path in objOrEnumerator) 

    {

        NSArray *assetItemsInSection = [[activeAssetSources objectAtIndex:path.section] items];

        AssetBrowserItem *assetItem = ((NSInteger)[assetItemsInSection count] > path.row) ? [assetItemsInSection objectAtIndex:path.row] : nil;

        if (assetItem) {

            __block NSInteger runningRequests = 0;

            if (assetItem.thumbnailImage == nil) {

                CGFloat targetHeight = self.tableView.rowHeight -1.0; // The contentView is one point smaller than the cell because of the divider.

                targetHeight *= thumbnailScale;

                CGFloat targetAspectRatio = 1.5;

                CGSize targetSize = CGSizeMake(targetHeight*targetAspectRatio, targetHeight);

                runningRequests++;

                [assetItem generateThumbnailAsynchronouslyWithSize:targetSize fillMode:AssetBrowserItemFillModeCrop completionHandler:^(UIImage *thumbnail)

                {

                    runningRequests--;

                    if (runningRequests == 0) {

                        [self updateCellForBrowserItemIfVisible:assetItem];

                        // Continue generating until all thumbnails/titles in range have been finished.

                        [self thumbnailsAndTitlesTask];

                    }

                }];

            }

            if (!assetItem.haveRichestTitle) {

                runningRequests++;

                [assetItem generateTitleFromMetadataAsynchronouslyWithCompletionHandler:^(NSString *title){

                    runningRequests--;

                    if (runningRequests == 0) {

                        [self updateCellForBrowserItemIfVisible:assetItem];

                        // Continue generating until all thumbnails/titles in range have been finished.

                        [self thumbnailsAndTitlesTask];

                    }

                }];

            }

            // If we are generating a title or thumbnail then wait until that returns to generate the next one.

            if ( runningRequests > 0 )

                return;

        }

    }

    thumbnailAndTitleGenerationIsRunning = NO;

    return;

}

- (void)enableThumbnailAndTitleGeneration

{

    thumbnailAndTitleGenerationEnabled = YES;

}

- (void)disableThumbnailAndTitleGeneration

{

    thumbnailAndTitleGenerationEnabled = NO;

}

- (void)generateThumbnailsAndTitles

{

    if (! thumbnailAndTitleGenerationEnabled) {

        return;

    }

    if (! thumbnailAndTitleGenerationIsRunning) {

        /* Run on the next run loop iteration. We may be called from with configureCell: and we don't want to slow down table view display. */

        thumbnailAndTitleGenerationIsRunning = YES;

        dispatch_async(dispatch_get_main_queue(), ^(void) {

            [self thumbnailsAndTitlesTask];

        });

    }

}

#pragma mark -

#pragma mark Deferred image loading (UIScrollViewDelegate)

#if ONLY_GENERATE_THUMBS_AND_TITLES_WHEN_NOT_SCROLLING

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView

{

    [self disableThumbnailAndTitleGeneration];

}

// Load images for all onscreen rows when scrolling is finished

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate

{

    if (!decelerate) {

        [self enableThumbnailAndTitleGeneration];

        [self generateThumbnailsAndTitles];

    }

}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView

{

    [self enableThumbnailAndTitleGeneration];

    [self generateThumbnailsAndTitles];

}

#endif //ONLY_GENERATE_THUMBS_AND_TITLES_WHEN_NOT_SCROLLING

- (void)scrollViewDidScroll:(UIScrollView *)scrollView

{   

    CGFloat newOffset = scrollView.contentOffset.y;

    CGFloat oldOffset = lastTableViewYContentOffset;

    CGFloat offsetAmount = newOffset-oldOffset;

    // Only update the scroll direction if we've passed some threshold (8 points).

    if ( fabs(offsetAmount) > 8.0 ) {

        if (offsetAmount > 0.0)

            lastTableViewScrollDirection = AssetBrowserScrollDirectionDown;

        else if (newOffset < oldOffset)

            lastTableViewScrollDirection = AssetBrowserScrollDirectionUp;

        lastTableViewYContentOffset = newOffset;

    }

}

#pragma mark -

#pragma mark Memory management

- (void)didReceiveMemoryWarning {

    // Releases the view if it doesn't have a superview.

    [super didReceiveMemoryWarning];

    // Get rid of AVAsset and thumbnail caches for items which aren't on screen.

    NSLog(@"%@ memory warning, clearing asset and thumbnail caches", self);

    NSArray *visibleIndexPaths = [self.tableView indexPathsForVisibleRows];

    NSUInteger section = 0;

    NSUInteger row = 0;

    for (AssetBrowserSource *source in activeAssetSources) {

        row = 0;

        for (AssetBrowserItem *item in [source items]) {

            NSIndexPath *path = [NSIndexPath indexPathForRow:row inSection:section];

            if (![visibleIndexPaths containsObject:path]) {

                [item clearAssetCache];

                [item clearThumbnailCache];

            }

            row++;

        }

        section++;

    }

}

- (void)dealloc 

{

    delegate = nil;

}

@end

@implementation UINavigationController (AssetBrowserConvenienceMethods)

+ (UINavigationController*)modalAssetBrowserControllerWithSourceType:(AssetBrowserSourceType)sourceType delegate:(id <AssetBrowserControllerDelegate>)delegate

{

    AssetBrowserController *browser = [[AssetBrowserController alloc] initWithSourceType:sourceType modalPresentation:YES];

    browser.delegate = delegate;

    UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:browser];

    [navController.navigationBar setBarStyle:UIBarStyleBlack];

    [navController.navigationBar setTranslucent:YES];

    return navController;

}

@end

@implementation UITabBarController (AssetBrowserConvenienceMethods)

+ (UITabBarController*)tabbedModalAssetBrowserControllerWithSourceType:(AssetBrowserSourceType)sourceType delegate:(id <AssetBrowserControllerDelegate>)delegate

{

    UITabBarController *tabBarController = [[UITabBarController alloc] init];

    NSMutableArray *assetBrowserControllers = [NSMutableArray arrayWithCapacity:0];

    if (sourceType & AssetBrowserSourceTypeCameraRoll) {

        [assetBrowserControllers addObject:[UINavigationController modalAssetBrowserControllerWithSourceType:AssetBrowserSourceTypeCameraRoll delegate:delegate]];

    }

    if (sourceType & AssetBrowserSourceTypeFileSharing) {

        [assetBrowserControllers addObject:[UINavigationController modalAssetBrowserControllerWithSourceType:AssetBrowserSourceTypeFileSharing delegate:delegate]];

    }

    if (sourceType & AssetBrowserSourceTypeIPodLibrary) {

        [assetBrowserControllers addObject:[UINavigationController modalAssetBrowserControllerWithSourceType:AssetBrowserSourceTypeIPodLibrary delegate:delegate]];

    }

    tabBarController.viewControllers = assetBrowserControllers;

    return tabBarController;

}

@end