/*

    File:       ImageDownloadOperation.m

    Contains:   Downloads an image to a directory.

    Written by: DTS

    Copyright:  Copyright (c) 2011-2013 Apple Inc. All Rights Reserved.

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

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                original Apple software (the "Apple Software"), to use,

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                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,

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                THE APPLE SOFTWARE OR ITS USE AND OPERATION ALONE OR IN

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*/

#import "ImageDownloadOperation.h"

#include <fcntl.h>

#include <unistd.h>

@interface ImageDownloadOperation ()

// Read/write versions of public properties

@property (atomic, copy,   readwrite) NSString *    imageFilePath;

@end

@implementation ImageDownloadOperation

@synthesize imagesDirPath = _imagesDirPath;

@synthesize depth         = _depth;

@synthesize imageFilePath = _imageFilePath;

- (id)initWithURL:(NSURL *)url imagesDirPath:(NSString *)imagesDirPath depth:(NSUInteger)depth

    // See comment in header.

{

    assert(imagesDirPath != nil);

    self = [super initWithURL:url];

    if (self != nil) {

        self->_imagesDirPath = [imagesDirPath copy];

        self->_depth = depth;

    }

    return self;

}

- (void)dealloc

{

    [self->_imageFilePath release];

    [self->_imagesDirPath release];

    [super dealloc];

}

+ (NSString *)defaultExtensionToMIMEType:(NSString *)type

    // See comment in header.

{

    static NSDictionary *   sTypeToExtensionMap;

    // This needs to be thread safe because the client could start multiple 

    // download operations with different run loop threads and, if so, 

    // +defaultExtensionToMIMEType: can get call by multiple threads simultaneously.

    @synchronized (self) {

        if (sTypeToExtensionMap == nil) {

            sTypeToExtensionMap = [@{

                @"image/gif":  @"gif", 

                @"image/png":  @"png", 

                @"image/jpeg": @"jpg", 

            } retain];

            assert(sTypeToExtensionMap != nil);

        }

    }

    return (type == nil) ? nil : [sTypeToExtensionMap objectForKey:type];

}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response

    // An NSURLConnect delegate method.  We override this to set up a 

    // destination output stream for the incoming image data.

{

    [super connection:connection didReceiveResponse:response];

    // If the response is an error, no need to do anything special here. 

    // We only need to set up an output stream if we're successfully 

    // getting the image.

    if (self.isStatusCodeAcceptable) {

        NSString *  extension;

        NSString *  prefix;

        assert(self.responseOutputStream == nil);

        // Create a unique file for the downloaded image.  Start by getting an appropriate 

        // extension.  If we don't have one, that's bad.

        extension = [[self class] defaultExtensionToMIMEType:[self.lastResponse MIMEType]];

        if (extension != nil) {

            NSString *  fileName;

            NSString *  filePath;

            int         counter;

            int         fd;

            // Next calculate the file name prefix and extension.

            fileName = [self.lastResponse suggestedFilename];

            if (fileName == nil) {

                prefix = @"image";

                assert(extension != nil);       // that is, the default

            } else {

                if ([[fileName pathExtension] length] == 0) {

                    prefix = fileName;

                    assert(extension != nil);   // that is, the default

                } else {

                    prefix    = [fileName stringByDeletingPathExtension];

                    extension = [fileName pathExtension];

                }

            }

            assert(prefix != nil);

            assert(extension != nil);

            // Repeatedly try to create a new file with that info, adding a 

            // unique number if we get a conflict.

            counter = 0;

            filePath = [self.imagesDirPath stringByAppendingPathComponent:[prefix stringByAppendingPathExtension:extension]];

            do {

                int     err;

                int     junk;

                err = 0;

                fd = open([filePath UTF8String], O_CREAT | O_EXCL | O_RDWR, 0666);

                if (fd < 0) {

                    err = errno;

                } else {

                    junk = close(fd);

                    assert(junk == 0);

                }

                if (err == 0) {

                    self.imageFilePath = filePath;

                    self.responseOutputStream = [NSOutputStream outputStreamToFileAtPath:filePath append:NO];

                    break;

                } else if (err == EEXIST) {

                    counter += 1;

                    if (counter > 500) {

                        break;

                    }

                    filePath = [self.imagesDirPath stringByAppendingPathComponent:[[NSString stringWithFormat:@"%@-%d", prefix, counter] stringByAppendingPathExtension:extension]];

                } else if (err == EINTR) {

                    // do nothing

                } else {

                    break;

                }

            } while (YES);

        }

        // If we've failed to create a valid file, redirect the output to the bit bucket.

        if (self.responseOutputStream == nil) {

            self.responseOutputStream = [NSOutputStream outputStreamToFileAtPath:@"/dev/null" append:NO];

        }

    }

}

@end