NSString+HTML.m

//
//  NSString+HTML.m
//  MWFeedParser
//
//  Copyright (c) 2010 Michael Waterfall
//  
//  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:
//  
//  1. The above copyright notice and this permission notice shall be included
//     in all copies or substantial portions of the Software.
//  
//  2. This Software cannot be used to archive or collect data such as (but not
//     limited to) that of events, news, experiences and activities, for the 
//     purpose of any concept relating to diary/journal keeping.
//  
//  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 "NSString+HTML.h"
#import "GTMNSString+HTML.h"

@implementation NSString (HTML)

#pragma mark - Instance Methods

- (NSString *)stringByConvertingHTMLToPlainText {
  
  // Pool
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
  
  // Character sets
  NSCharacterSet *stopCharacters = [NSCharacterSet characterSetWithCharactersInString:[NSString stringWithFormat:@"< \t\n\r%d%d%d%d", 0x0085, 0x000C, 0x2028, 0x2029]];
  NSCharacterSet *newLineAndWhitespaceCharacters = [NSCharacterSet characterSetWithCharactersInString:[NSString stringWithFormat:@" \t\n\r%d%d%d%d", 0x0085, 0x000C, 0x2028, 0x2029]];
  NSCharacterSet *tagNameCharacters = [NSCharacterSet characterSetWithCharactersInString:@"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"];
  
  // Scan and find all tags
  NSMutableString *result = [[NSMutableString alloc] initWithCapacity:self.length];
  NSScanner *scanner = [[NSScanner alloc] initWithString:self];
  [scanner setCharactersToBeSkipped:nil];
  [scanner setCaseSensitive:YES];
  NSString *str = nil, *tagName = nil;
  BOOL dontReplaceTagWithSpace = NO;
  do {
    
    // Scan up to the start of a tag or whitespace
    if ([scanner scanUpToCharactersFromSet:stopCharacters intoString:&str]) {
      [result appendString:str];
      str = nil; // reset
    }
    
    // Check if we've stopped at a tag/comment or whitespace
    if ([scanner scanString:@"<" intoString:NULL]) {
      
      // Stopped at a comment or tag
      if ([scanner scanString:@"!--" intoString:NULL]) {
        
        // Comment
        [scanner scanUpToString:@"-->" intoString:NULL]; 
        [scanner scanString:@"-->" intoString:NULL];
        
      } else {
        
        // Tag - remove and replace with space unless it's
        // a closing inline tag then dont replace with a space
        if ([scanner scanString:@"/" intoString:NULL]) {
          
          // Closing tag - replace with space unless it's inline
          tagName = nil; dontReplaceTagWithSpace = NO;
          if ([scanner scanCharactersFromSet:tagNameCharacters intoString:&tagName]) {
            tagName = [tagName lowercaseString];
            dontReplaceTagWithSpace = ([tagName isEqualToString:@"a"] ||
                           [tagName isEqualToString:@"b"] ||
                           [tagName isEqualToString:@"i"] ||
                           [tagName isEqualToString:@"q"] ||
                           [tagName isEqualToString:@"span"] ||
                           [tagName isEqualToString:@"em"] ||
                           [tagName isEqualToString:@"strong"] ||
                           [tagName isEqualToString:@"cite"] ||
                           [tagName isEqualToString:@"abbr"] ||
                           [tagName isEqualToString:@"acronym"] ||
                           [tagName isEqualToString:@"label"]);
          }
          
          // Replace tag with string unless it was an inline
          if (!dontReplaceTagWithSpace && result.length > 0 && ![scanner isAtEnd]) [result appendString:@" "];
          
        }
        
        // Scan past tag
        [scanner scanUpToString:@">" intoString:NULL];
        [scanner scanString:@">" intoString:NULL];
        
      }
      
    } else {
      
      // Stopped at whitespace - replace all whitespace and newlines with a space
      if ([scanner scanCharactersFromSet:newLineAndWhitespaceCharacters intoString:NULL]) {
        if (result.length > 0 && ![scanner isAtEnd]) [result appendString:@" "]; // Dont append space to beginning or end of result
      }
      
    }
    
  } while (![scanner isAtEnd]);
  
  // Cleanup
  [scanner release];
  
  // Decode HTML entities and return
  NSString *retString = [[result stringByDecodingHTMLEntities] retain];
  [result release];
  
  // Drain
  [pool drain];
  
  // Return
  return [retString autorelease];
  
}

- (NSString *)stringByDecodingHTMLEntities {
    // Can return self so create new string if we're a mutable string
    return [NSString stringWithString:[self gtm_stringByUnescapingFromHTML]];
}


- (NSString *)stringByEncodingHTMLEntities {
    // Can return self so create new string if we're a mutable string
    return [NSString stringWithString:[self gtm_stringByEscapingForAsciiHTML]];
}

- (NSString *)stringByEncodingHTMLEntities:(BOOL)isUnicode {
    // Can return self so create new string if we're a mutable string
    return [NSString stringWithString:(isUnicode ? [self gtm_stringByEscapingForHTML] : [self gtm_stringByEscapingForAsciiHTML])];
}

- (NSString *)stringWithNewLinesAsBRs {
  
  // Pool
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
  
  // Strange New lines:
  //  Next Line, U+0085
  //  Form Feed, U+000C
  //  Line Separator, U+2028
  //  Paragraph Separator, U+2029
  
  // Scanner
  NSScanner *scanner = [[NSScanner alloc] initWithString:self];
  [scanner setCharactersToBeSkipped:nil];
  NSMutableString *result = [[NSMutableString alloc] init];
  NSString *temp;
  NSCharacterSet *newLineCharacters = [NSCharacterSet characterSetWithCharactersInString:
                     [NSString stringWithFormat:@"\n\r%d%d%d%d", 0x0085, 0x000C, 0x2028, 0x2029]];
  // Scan
  do {
    
    // Get non new line characters
    temp = nil;
    [scanner scanUpToCharactersFromSet:newLineCharacters intoString:&temp];
    if (temp) [result appendString:temp];
    temp = nil;
    
    // Add <br /> s
    if ([scanner scanString:@"\r\n" intoString:nil]) {
      
      // Combine \r\n into just 1 <br />
      [result appendString:@"<br />"];
      
    } else if ([scanner scanCharactersFromSet:newLineCharacters intoString:&temp]) {
      
      // Scan other new line characters and add <br /> s
      if (temp) {
        for (NSUInteger i = 0; i < temp.length; i++) {
          [result appendString:@"<br />"];
        }
      }
      
    }
    
  } while (![scanner isAtEnd]);
  
  // Cleanup & return
  [scanner release];
  NSString *retString = [[NSString stringWithString:result] retain];
  [result release];
  
  // Drain
  [pool drain];
  
  // Return
  return [retString autorelease];
  
}

- (NSString *)stringByRemovingNewLinesAndWhitespace {
  
  // Pool
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
  
  // Strange New lines:
  //  Next Line, U+0085
  //  Form Feed, U+000C
  //  Line Separator, U+2028
  //  Paragraph Separator, U+2029
  
  // Scanner
  NSScanner *scanner = [[NSScanner alloc] initWithString:self];
  [scanner setCharactersToBeSkipped:nil];
  NSMutableString *result = [[NSMutableString alloc] init];
  NSString *temp;
  NSCharacterSet *newLineAndWhitespaceCharacters = [NSCharacterSet characterSetWithCharactersInString:
                            [NSString stringWithFormat:@" \t\n\r%d%d%d%d", 0x0085, 0x000C, 0x2028, 0x2029]];
  // Scan
  while (![scanner isAtEnd]) {
    
    // Get non new line or whitespace characters
    temp = nil;
    [scanner scanUpToCharactersFromSet:newLineAndWhitespaceCharacters intoString:&temp];
    if (temp) [result appendString:temp];
    
    // Replace with a space
    if ([scanner scanCharactersFromSet:newLineAndWhitespaceCharacters intoString:NULL]) {
      if (result.length > 0 && ![scanner isAtEnd]) // Dont append space to beginning or end of result
        [result appendString:@" "];
    }
    
  }
  
  // Cleanup
  [scanner release];
  
  // Return
  NSString *retString = [[NSString stringWithString:result] retain];
  [result release];
  
  // Drain
  [pool drain];
  
  // Return
  return [retString autorelease];
  
}

- (NSString *)stringByLinkifyingURLs {
    if (!NSClassFromString(@"NSRegularExpression")) return self;
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    NSString *pattern = @"(?<!=\")\\b((http|https):\\/\\/[\\w\\-_]+(\\.[\\w\\-_]+)+([\\w\\-\\.,@?^=%%&amp;:/~\\+#]*[\\w\\-\\@?^=%%&amp;/~\\+#])?)";
    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern options:0 error:nil];
    NSString *modifiedString = [[regex stringByReplacingMatchesInString:self options:0 range:NSMakeRange(0, [self length])
                                                           withTemplate:@"<a href=\"$1\" class=\"linkified\">$1</a>"] retain];
    [pool drain];
    return [modifiedString autorelease];
}

- (NSString *)stringByStrippingTags {
  
  // Pool
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
  
  // Find first & and short-cut if we can
  NSUInteger ampIndex = [self rangeOfString:@"<" options:NSLiteralSearch].location;
  if (ampIndex == NSNotFound) {
    return [NSString stringWithString:self]; // return copy of string as no tags found
  }
  
  // Scan and find all tags
  NSScanner *scanner = [NSScanner scannerWithString:self];
  [scanner setCharactersToBeSkipped:nil];
  NSMutableSet *tags = [[NSMutableSet alloc] init];
  NSString *tag;
  do {
    
    // Scan up to <
    tag = nil;
    [scanner scanUpToString:@"<" intoString:NULL];
    [scanner scanUpToString:@">" intoString:&tag];
    
    // Add to set
    if (tag) {
      NSString *t = [[NSString alloc] initWithFormat:@"%@>", tag];
      [tags addObject:t];
      [t release];
    }
    
  } while (![scanner isAtEnd]);
  
  // Strings
  NSMutableString *result = [[NSMutableString alloc] initWithString:self];
  NSString *finalString;
  
  // Replace tags
  NSString *replacement;
  for (NSString *t in tags) {
    
    // Replace tag with space unless it's an inline element
    replacement = @" ";
    if ([t isEqualToString:@"<a>"] ||
      [t isEqualToString:@"</a>"] ||
      [t isEqualToString:@"<span>"] ||
      [t isEqualToString:@"</span>"] ||
      [t isEqualToString:@"<strong>"] ||
      [t isEqualToString:@"</strong>"] ||
      [t isEqualToString:@"<em>"] ||
      [t isEqualToString:@"</em>"]) {
      replacement = @"";
    }
    
    // Replace
    [result replaceOccurrencesOfString:t 
                withString:replacement
                   options:NSLiteralSearch 
                   range:NSMakeRange(0, result.length)];
  }
  
  // Remove multi-spaces and line breaks
  finalString = [[result stringByRemovingNewLinesAndWhitespace] retain];
  
  // Cleanup
  [result release];
  [tags release];
  
  // Drain
  [pool drain];
  
  // Return
    return [finalString autorelease];
  
}

static NSDictionary *htmlEscapes = nil;
static NSDictionary *htmlUnescapes = nil;

+ (NSDictionary *)htmlEscapes {
  if (!htmlEscapes) {
    htmlEscapes = [[NSDictionary alloc] initWithObjectsAndKeys:
                   @"&amp;", @"&",
                   @"&lt;", @"<",
                   @"&gt;", @">",
                   nil
                   ];
  }
  return htmlEscapes;
}

+ (NSDictionary *)htmlUnescapes {
  if (!htmlUnescapes) {
    htmlUnescapes = [[NSDictionary alloc] initWithObjectsAndKeys:
                     @"\n", @"<br>",
                     @"\n", @"<p>",
                     @"", @"</p>",
                     @"", @"<ol>",
                     @"", @"</ol>",
                     @"", @"<li>",
                     @"\n", @"</li>",
                     @"", @"<em>",
                     @"", @"</em>",
                     @"", @"<div>",
                     @"\n", @"</div>",
                     @"", @"<b>",
                     @"", @"</b>",
                     @"", @"<i>",
                     @"", @"</i>",
                     @"", @"<span>",
                     @"", @"</span>",
                     @"", @"<strong>",
                     @"", @"</strong>",
                     @"&", @"&amp;",
                     @"<", @"&lt;",
                     @">", @"&gt;",
                     //@"\n", @"&nbsp;",
                     nil
                     ];
  }
  return htmlUnescapes;
}

static NSString *replaceAll(NSString *s, NSDictionary *replacements) {
  for (NSString *key in replacements) {
    NSString *replacement = [replacements objectForKey:key];
    s = [s stringByReplacingOccurrencesOfString:key withString:replacement];
  }
  return s;
}

- (NSString *)htmlEscapedString {
  return replaceAll(self, [[self class] htmlEscapes]);
}

- (NSString *)htmlUnescapedString {
  return replaceAll(self, [[self class] htmlUnescapes]);
}

@end