NATIVE Persistent LocalStorage Phonegap Support

/*
 *
 * PERSISTENT LOCALSTORAGE NATIVE SOLUTION for phonegap (tested on 1.3)
 * iOS 5.1 puts LocalStorage in a vulnerable location (Libary/Caches). This will copy it to
 * the documents folder as "appdata.db" so that it will be appropriately backed-up and not
 * overwritten. If "appdata.db" doesn't exist, localStorage will not be overwritten.
 * Also, upon application suspend (resignActive) or termination, localStorage is saved, so
 * there should not be any chance that changes to localStorage won't be persisted. [[ short of a power-cycle ]]
 *
 * The following should be placed in AppDelegate.m. Note that it //partially// replaces
 * webViewDidStartLoad:. The remainder of webViewDidStartLoad: (as in phonegap 1.3) is below,
 * replace/remove as appropriate
 *
 * @Author: Kerri Shotts (2012)
 * @License: MIT License
 *
 * Notes: USES ARC. IF USING MRC, apply the appropriate releases.
 *
 * Based partially on http://gauravstomar.blogspot.com/2011/08/prepopulate-sqlite-in-phonegap.html
 *
 */
- (BOOL)fileExists: (NSString*) theFile
{
    NSFileManager *fileManager = [NSFileManager defaultManager];
    return [fileManager fileExistsAtPath:theFile];
    // MRC: make sure to release
}

- (void)copyFile:(NSString*) sourceFile to:(NSString*) targetPath withName:(NSString*) targetFile
{
    NSFileManager *fileManager = [NSFileManager defaultManager];
    [fileManager createDirectoryAtPath:targetPath withIntermediateDirectories:YES attributes:nil error:NULL];
    NSString *fullTargetFile = [targetPath stringByAppendingPathComponent:targetFile];

    NSLog(@"Source File for Copy: %@", sourceFile);
    NSLog(@"Target File for Copy: %@", fullTargetFile);

    if ( [self fileExists:fullTargetFile] )
    {
        // remove the file first. (Ick! I wish there was a better way...
        if ( [fileManager removeItemAtPath:fullTargetFile error:nil] == YES )
        {
            NSLog (@"Target successfully removed.");
        }
        else
        {
            NSLog (@"Target could not be removed prior to copy. No copy will occur.");
            return;
        }
    }

    if ( [fileManager copyItemAtPath:sourceFile toPath:fullTargetFile error:nil] == YES)
    {
        NSLog(@"Copy successful.");
    }
    else
    {
        NSLog(@"Copy unsuccessful.");
    }
    // MRC: don't forget to release fileManager where necessary!
}


- (BOOL)isIOS5_1OrHigher
{
    // based on: http://stackoverflow.com/a/9320041
    NSArray *versionCompatibility = [[UIDevice currentDevice].systemVersion componentsSeparatedByString:@"."];

    if ( [[versionCompatibility objectAtIndex:0] intValue] > 5 )
    {
        return YES; // iOS 6+
    }

    if ( [[versionCompatibility objectAtIndex:0] intValue] < 5 )
    {
        return NO;  // iOS 4.x or lower
    }

    if ( [[versionCompatibility objectAtIndex:1] intValue] >= 1 )
    {
        return YES; // ios 5.<<1>> or higher
    }

    return NO;  // ios 5.<<0.x>> or lower

}

- (void)copyPersistentStorageToLocalStorage
{
    // build localStorage path: ~/Library/WebKit/LocalStorage/file__0.localstorage (for iOS < 5.1)
    //                          ~/Library/Caches/file__0.localstorage (for iOS >= 5.1 )
    NSString *localStoragePath;
    if ( [self isIOS5_1OrHigher] )
    {
        // for IOS >= 5.1
        localStoragePath =
                          [
                           [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) objectAtIndex:0]
                           stringByAppendingPathComponent:@"Caches"
                          ];
    }
    else
    {
        // for IOS < 5.1;
        localStoragePath =
                          [
                           [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) objectAtIndex:0]
                           stringByAppendingPathComponent:@"WebKit/LocalStorage"
                          ];
    }

    // build persistentStorage path: ~/Documents/appdata.db
    NSString *persistentStoragePath =
                                   [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *persistentStorageFile = [persistentStoragePath stringByAppendingPathComponent:@"appdata.db"];

    // does the persistent store exist?
    if ([self fileExists:persistentStorageFile ])
    {
        // it does, copy it over localStorage
        NSLog(@"Copying persistent storage to local storage.");
        [self copyFile:persistentStorageFile to:localStoragePath withName: @"file__0.localstorage"];
    }
    else
    {
        NSLog(@"No persistent storage to copy. Using local storage only.");
    }
}

- (void)copyLocalStorageToPersistentStorage
{
    // build localStorage path: ~/Library/WebKit/LocalStorage/file__0.localstorage (for iOS < 5.1)
    //                          ~/Library/Caches/file__0.localstorage (for iOS >= 5.1 )
    NSString *localStoragePath;
    if ( [self isIOS5_1OrHigher] )
    {
        // for IOS >= 5.1
        localStoragePath =
                          [
                           [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) objectAtIndex:0]
                           stringByAppendingPathComponent:@"Caches"
                          ];
    }
    else
    {
        // for IOS < 5.1;
        localStoragePath =
                          [
                           [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) objectAtIndex:0]
                           stringByAppendingPathComponent:@"WebKit/LocalStorage"
                          ];
    }

    NSString *localStorageFile = [localStoragePath stringByAppendingPathComponent:@"file__0.localstorage"];

    // build persistentStorage path: ~/Documents/appdata.db
    NSString *persistentStoragePath =
                                   [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];

    // does the local store exist? (it almost always will)
    if ([self fileExists:localStorageFile ])
    {
        // it does, copy it over persistent Storage
        NSLog(@"Copying local storage to persistent storage.");
        [self copyFile:localStorageFile to:persistentStoragePath withName:@"appdata.db"];
    }
    else
    {
        NSLog(@"No local storage to copy. Using local storage only.");
    }

}

- (void)applicationWillResignActive:(UIApplication *)application
{
    // move the local storage data to persistent storage
    // while we're resigning so that we know our data is safe...
    [self copyLocalStorageToPersistentStorage];
    return;
}

- (void)applicationWillTerminate:(UIApplication *)application
{
    // move the local storage data to persistent storage
    // while we're terminating so that we know our data is safe...
    [self copyLocalStorageToPersistentStorage];
    return;
}

- (void)webViewDidStartLoad:(UIWebView *)theWebView
{
    [self copyPersistentStorageToLocalStorage];
//
// END Persistent LocalStorage solution. Remainder of webViewDidStartLoad: should be used.
//
    return [ super webViewDidStartLoad:theWebView ];
}