NSXMLParser+ReactiveCocoa.m

//
//  NSXMLParser+ReactiveCocoa.m
//
//
//  The MIT License (MIT)
//
//  Copyright (c) 2014 Alex Manarpies
//
//  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 "NSXMLParser+ReactiveCocoa.h"
#import "NSXMLParserRACDelegate.h"
#import "NSXMLParserRACElement.h"

#import <ReactiveCocoa.h>

@implementation NSXMLParser (ReactiveCocoa)

+ (RACSignal *)rac_parseURL:(NSURL *)url
{
    return [self rac_parseWithParser:[[NSXMLParser alloc] initWithContentsOfURL:url]];
}

+ (RACSignal *)rac_parseData:(NSData *)data
{
    return [self rac_parseWithParser:[[NSXMLParser alloc] initWithData:data]];
}

+ (RACSignal *)rac_dictionaryFromString:(NSString *)string elementFilter:(ElementFilterBlock)filterBlock
{
    NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
    return [self rac_dictionaryFromData:data elementFilter:filterBlock];
}

+ (RACSignal *)rac_dictionaryFromURL:(NSURL *)url elementFilter:(ElementFilterBlock)filterBlock
{
    return [self rac_dictionaryFromSignal:[self rac_parseURL:url] elementfilter:filterBlock];
}

+ (RACSignal *)rac_dictionaryFromData:(NSData *)data elementFilter:(ElementFilterBlock)filterBlock
{
    return [self rac_dictionaryFromSignal:[self rac_parseData:data] elementfilter:filterBlock];
}

- (RACSignal *)rac_parser
{
    return [NSXMLParser rac_parseWithParser:self];
}

- (RACSignal *)rac_parserWithElementFilter:(ElementFilterBlock)filterBlock
{
    return [NSXMLParser rac_dictionaryFromSignal:[self rac_parser] elementfilter:filterBlock];
}

#pragma mark - Internal

/**
 * Parse a XML using a pre-init'ed parser.
 */
+ (RACSignal *)rac_parseWithParser:(NSXMLParser *)parser
{
    return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {

        return [[RACScheduler scheduler] schedule:^{
            NSXMLParserRACDelegate *delegate = [[NSXMLParserRACDelegate alloc] init];
            [delegate.elementParsed subscribe:subscriber];

            parser.delegate = delegate;
            [parser parse];
        }];
    }];
}

+ (RACSignal *)rac_dictionaryFromSignal:(RACSignal *)signal elementfilter:(ElementFilterBlock)filterBlock
{
    // Parsing algorythm inspired by http://troybrant.net/blog/2010/09/simple-xml-to-nsdictionary-converter
    return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        return [[RACScheduler scheduler] schedule:^{
            __block NSMutableArray *stack = [@[[@{} mutableCopy]] mutableCopy];
            __block NSXMLParserRACElement *currentElement;

            [[signal filter:^BOOL(NSXMLParserRACElement *element) {
                // If provided delegate to filterBlock to determine which elements to ignore
                return filterBlock ? filterBlock(element.name) : YES;

            }] subscribeNext:^(NSXMLParserRACElement *element) {
                if (element.phase == NSXMLParserRACElementPhaseOpen) {
                    NSMutableDictionary *parent = [stack lastObject];
                    NSMutableDictionary *child = [@{} mutableCopy];

                    if ([element.attributes count]) {
                        for (NSString *key in [element.attributes allKeys]) {
                            child[key] = element.attributes[key];
                        }
                    }

                    id existing = parent[element.name];
                    if (existing) {
                        NSMutableArray *array = nil;
                        if ([existing isKindOfClass:[NSMutableArray class]]) {
                            array = existing;
                        }
                        else {
                            array = [@[] mutableCopy];
                            [array addObject:existing];

                            parent[element.name] = array;
                        }

                        [array addObject:child];
                    }
                    else {
                        parent[element.name] = child;
                    }

                    [stack addObject:child];
                }

                if (element.phase == NSXMLParserRACElementPhaseData) {
                    currentElement = element;
                }

                if (element.phase == NSXMLParserRACElementPhaseClose) {
                    NSMutableDictionary *current = [stack lastObject];
                    if (currentElement.body) {
                        NSString *sanitized = [currentElement.body stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
                        if (sanitized && ![sanitized isEqualToString:@""]) {
                            current[@"text"] = sanitized;
                        }
                    }

                    [stack removeLastObject];
                }

            }          error:^(NSError *error) {
                [subscriber sendError:error];

            }      completed:^{
                if ([stack count] > 0) [subscriber sendNext:stack[0]];
                [subscriber sendCompleted];
            }];
        }];
    }];
}

@end