FRCoreDataExportOperation.m

//
//  FRCoreDataExportOperation.m
//
//  Created by Jonathan Dalrymple on 11/11/2012.
//
//  Copyright (C) 2012 Jonathan Dalrymple
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE // USE OR OTHER DEALINGS IN THE SOFTWARE.
//

#import "FRCoreDataExportOperation.h"

@interface FRCoreDataExportOperation ()

@property (nonatomic,copy,readwrite) NSString *fileName;
@property (nonatomic,copy,readwrite) NSPredicate *predicate;
@property (nonatomic,copy,readwrite) NSArray *sortDescriptors;
@property (nonatomic,strong,readwrite) NSEntityDescription *entityDescription;

@end

@implementation FRCoreDataExportOperation

#pragma mark - Object creation
- (id)initWithEntityName:(NSString *)aName
    managedObjectContext:(NSManagedObjectContext *)aMOC {
  
  self = [super initWithManagedObjectContext:aMOC];
  if (self) {
    [self setEntityDescription:[NSEntityDescription entityForName:aName
                                           inManagedObjectContext:aMOC]];
  }
  return self;
}

- (id)initWithEntityName:(NSString *)aName
               predicate:(NSPredicate *)aPredicate
    managedObjectContext:(NSManagedObjectContext *)aMOC {
  
  self = [self initWithEntityName:aName
             managedObjectContext:aMOC];
  if (self) {
    [self setPredicate:aPredicate];
  }
  return self;
}

- (id)initWithEntityName:(NSString *)aName
               predicate:(NSPredicate *)aPredicate
         sortDescriptors:(NSArray *)sortDescriptors
    managedObjectContext:(NSManagedObjectContext *)aMOC {
  
  self = [self initWithEntityName:aName
             managedObjectContext:aMOC];
  if (self) {
    [self setPredicate:aPredicate];
    [self setSortDescriptors:sortDescriptors];
  }
  return self;
}

#pragma mark - Formatting

- (NSString *)entityName {
  return [[self entityDescription] name];
}

- (void)setEntityFormatter:(id<FRCoreDataEntityFormatter>)aFormatter {
  
  NSAssert(![self isExecuting], @"Cannot change the operation once it has started");
  
  _entityFormatter = nil;
  _entityFormatter = aFormatter;
  
}

- (void)setFileName:(NSString *)aFileName {
	
  NSAssert(![self isExecuting], @"Cannot change the operation once it has started");
	
	_fileName = nil;
	_fileName = [aFileName copy];
	
}

#pragma mark - Object stringification
-(id)transformValue:(id)aValue withAttributeName:(NSString *)aName {
  
  id returnValue = [NSNull null];
  
  //Attempt to transform value based on type where the value is not nil
  if ([aValue isKindOfClass:[NSNumber class]]
      && [[self entityFormatter] respondsToSelector:@selector(transformNumberValue:withAttributeName:)] ) {

      returnValue = [[self entityFormatter] transformNumberValue:aValue
                                               withAttributeName:aName];
  }
  else if ([aValue isKindOfClass:[NSString class]]
           && [[self entityFormatter] respondsToSelector:@selector(transformStringValue:withAttributeName:)]) {
    
    returnValue = [[self entityFormatter] transformStringValue:aValue
                                             withAttributeName:aName];
  
  }
  else if ([aValue isKindOfClass:[NSDate class]]
           && [[self entityFormatter] respondsToSelector:@selector(transformDateValue:withAttributeName:)]) {
    
    returnValue = [[self entityFormatter] transformDateValue:aValue
                                           withAttributeName:aName];
    
  }
  else if ([aValue isKindOfClass:[NSData class]]
           && [[self entityFormatter] respondsToSelector:@selector(transformDataValue:withAttributeName:)]) {

    returnValue = [[self entityFormatter] transformDataValue:aValue
                                           withAttributeName:aName];

  }
  else if (aValue && [[self entityFormatter] respondsToSelector:@selector(transformValue:withAttributeName:)]) {

    returnValue = [[self entityFormatter] transformValue:aValue
                                withAttributeName:aName];
  }
  else if (aValue) {  //If there is no formatter and the value is not nil return as is.
    returnValue = aValue;
  }
  
  //execution should only reach here is the value is nil
  return returnValue;
}

- (NSDictionary *)dictionaryRepresentationOfManagedObject:(NSManagedObject *)aObject {
  return [self dictionaryRepresentationOfManagedObject:aObject
                                             recursive:YES];
}

- (NSDictionary *)dictionaryRepresentationOfManagedObject:(NSManagedObject *)aObject
                                                recursive:(BOOL)isRecursive {

  NSMutableDictionary *dictionary;
  NSDictionary *attributes;
  
  attributes = [[aObject entity] attributesByName];
  
  dictionary = [NSMutableDictionary dictionaryWithCapacity:[attributes count]];
  
  for (NSString *key in [attributes allKeys]) {
    
    [dictionary setObject:[self transformValue:[aObject valueForKey:key] withAttributeName:key]
                   forKey:key];
  }
	
	//Append the relationships to the dictionary
  if (isRecursive) {
    [dictionary addEntriesFromDictionary:[self dictionaryRepresentationOfRelationshipsWithManagedObject:aObject]];
  }
  
  return [dictionary copy];
  
}

- (NSDictionary *)dictionaryRepresentationOfRelationshipsWithManagedObject:(NSManagedObject *)aObject {
  
	NSDictionary *relationships = [[aObject entity] relationshipsByName];
	NSDictionary *dictionary;
	
	for (NSString *key in [relationships allKeys]) {
    
		NSRelationshipDescription *relationship = [relationships objectForKey:key];
		NSMutableArray *objects;
    
		//Handle one to one relationships
		//break the loop
		if (![relationship isToMany]) {
			dictionary = @{
                  key:[self dictionaryRepresentationOfManagedObject:[aObject valueForKey:key] recursive:NO]
                  };
			break;
		}
		
		//Initialize the array and get the capacity
		objects = [NSMutableArray arrayWithCapacity:[[aObject valueForKey:key] count]];
		
		//Handle one to many relationships
		for (NSManagedObject *obj in [aObject valueForKey:key]) {
			[objects addObject:[self dictionaryRepresentationOfManagedObject:obj
                                                             recursive:NO]];
		}
		
		dictionary = @{key:objects};
	}
	
	return dictionary;
}

- (NSString *)filePath {
  
  NSString *fileName = nil;
  
	if (!(fileName = [self fileName])) {
		fileName = [NSString stringWithFormat:@"%@.dat",[[self entityName] lowercaseString]];
	}
  
  return [NSString pathWithComponents:@[
          NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0],
          fileName
          ]];
  
}

#pragma mark - Object formatting proxy
- (NSData *)dataForManagedObject:(NSManagedObject *)aObject {
  
  return [[self entityFormatter] dataForDictionaryRespresentation:[self dictionaryRepresentationOfManagedObject:aObject]
                                                         ofEntity:[self entityDescription]];
}

#pragma mark - Main
- (void)main {
  
  NSEntityDescription *entityDescription = nil;
  NSFetchRequest *fetchRequest = nil;
  NSFileHandle *fileHandle = nil;
  NSDictionary *attributes = nil;
  NSArray *results = nil;
  NSError *error = nil;
  
  
  @autoreleasepool {
    
    fetchRequest = [[NSFetchRequest alloc] init];
    
    [fetchRequest setPredicate:[self predicate]];
    
    entityDescription = [NSEntityDescription entityForName:[self entityName]
                                    inManagedObjectContext:[self threadContext]];
    
    NSAssert(entityDescription, @"Invalid Entity %@",[self entityName]);
    
    [fetchRequest setEntity:entityDescription];
    
    //Fetch all the objects within the predicate
    results = [[self threadContext] executeFetchRequest:fetchRequest
                                                  error:&error];
    
    NSLog(@"Exporting %lu %@ objects",[results count],[self entityName]);
    
    if (!results || error) {
    	NSLog(@"Fetch error %@",error);
    }
    
    //Reuse the error prtr
    error = nil;
    
    ///////////////////////////////
    // Prepare the file for writing
    ///////////////////////////////
    
    // Open a mapped NSMutableData
    NSFileManager *fileManager = [[NSFileManager alloc] init];
    
    if ([fileManager fileExistsAtPath:[self filePath]]) {
      [fileManager removeItemAtPath:[self filePath]
                              error:&error];
    }
    
    [fileManager createFileAtPath:[self filePath]
                         contents:[NSData data]
                       attributes:nil];
    
    fileHandle = [NSFileHandle fileHandleForWritingAtPath:[self filePath]];
    
    if (!fileHandle || error ) {
      NSLog(@"File error %@",error);
    }
    
    attributes = [entityDescription attributesByName];
    
    //Header
    if ([[self entityFormatter] respondsToSelector:@selector(dataForHeaderOfEntity:)]) {
      [fileHandle writeData:[[self entityFormatter] dataForHeaderOfEntity:[self entityDescription]]];
    }
    
    //Exact the attribute names and print them
    for (NSUInteger i=0; i < [results count]; i++) {
      
      NSManagedObject *obj = (NSManagedObject *)[results objectAtIndex:i];
      
      //Keep the object overhead low
      @autoreleasepool {
        
        NSData *data;
        
        data = [[self entityFormatter] dataForDictionaryRespresentation:[self dictionaryRepresentationOfManagedObject:obj]
                                                               ofEntity:[self entityDescription]];
        
        [fileHandle writeData:data];
        
        //Insert the delimiter
        if ( i < ([results count]-1) ) {
          [fileHandle writeData:[[self entityFormatter] dataForObjectDelimiterOfEntity:[self entityDescription]]];
        }
        
        //Force the object we've just read to fault to
        [[self threadContext] refreshObject:obj
                               mergeChanges:NO];
        
      }
    }
    
    // Append the Footer
    if ([[self entityFormatter] respondsToSelector:@selector(dataForFooterOfEntity:)]) {
      [fileHandle writeData:[[self entityFormatter] dataForFooterOfEntity:[self entityDescription]]];
    }
    
    //Reuse the error prtr
    error = nil;
    
    //Close the file
    [fileHandle closeFile];
    
    if (error) {
      NSLog(@"File Error %@",error);
    }
    
  }
  
}

@end