ParagraphAttributesUtils.mm

#import "ParagraphAttributesUtils.h"
#import "EnrichedTextInputView.h"
#import "StyleHeaders.h"
#import "ParagraphsUtils.h"
#import "TextInsertionUtils.h"

@implementation ParagraphAttributesUtils

// if the user backspaces the last character in a line, the iOS applies typing attributes from the previous line
// in the case of some paragraph styles it works especially bad when a list point just appears
// hence the solution - reset typing attributes
+ (BOOL)handleBackspaceInRange:(NSRange)range replacementText:(NSString *)text input:(id)input {
  EnrichedTextInputView *typedInput = (EnrichedTextInputView *)input;
  UnorderedListStyle *ulStyle = typedInput->stylesDict[@([UnorderedListStyle getStyleType])];
  OrderedListStyle *olStyle = typedInput->stylesDict[@([OrderedListStyle getStyleType])];
  BlockQuoteStyle *bqStyle = typedInput->stylesDict[@([BlockQuoteStyle getStyleType])];
  
  if(typedInput == nullptr) {
    return NO;
  }
  
  // we make sure it was a backspace (text with 0 length) and it deleted something (range longer than 0)
  if(text.length > 0 || range.length == 0) {
    return NO;
  }
  
  // find a non-newline range of the paragraph
  NSRange paragraphRange = [typedInput->textView.textStorage.string paragraphRangeForRange:range];
  
  NSArray *paragraphs = [ParagraphsUtils getNonNewlineRangesIn:typedInput->textView range:paragraphRange];
  if(paragraphs.count == 0) {
    return NO;
  }
  
  NSRange nonNewlineRange = [(NSValue *)paragraphs.firstObject rangeValue];
  
  // if the backspace removes the whole content of a paragraph, we remove the typing attributes
  if(NSEqualRanges(nonNewlineRange, range)) {
  
    // edge case with lists and blockquotes:
    // for some reason, removing all characters from a list point that is: both the first point of a list and is the last thing in the input, doesn't preserve typing attributes
    // so we manually remove the characters and reapply attribtues for zero width space to appear there
    // otherwise (there still is list or quote) we don't want no actions because attributes are properly preserved and zero width space appears
    if([ulStyle detectStyle:paragraphRange]) {
      if(NSMaxRange(nonNewlineRange) == typedInput->textView.textStorage.string.length) {
        // manually remove the characters
        [TextInsertionUtils replaceText:text at:range additionalAttributes:nullptr input:typedInput withSelection:YES];
        // add atributes again
        [ulStyle addAttributes:NSMakeRange(range.location, 0)];
        return YES;
      }
      return NO;
    }
    if([olStyle detectStyle:paragraphRange]) {
      if(NSMaxRange(nonNewlineRange) == typedInput->textView.textStorage.string.length) {
        // manually remove the characters
        [TextInsertionUtils replaceText:text at:range additionalAttributes:nullptr input:typedInput withSelection:YES];
        // add atributes again
        [olStyle addAttributes:NSMakeRange(range.location, 0)];
        return YES;
      }
      return NO;
    }
    if([bqStyle detectStyle:paragraphRange]) {
      if(NSMaxRange(nonNewlineRange) == typedInput->textView.textStorage.string.length) {
        // manually remove the characters
        [TextInsertionUtils replaceText:text at:range additionalAttributes:nullptr input:typedInput withSelection:YES];
        // add atributes again
        [bqStyle addAttributes:NSMakeRange(range.location, 0)];
        return YES;
      }
      return NO;
    }
  
    // do the replacement manually
    [TextInsertionUtils replaceText:text at:range additionalAttributes:nullptr input:typedInput withSelection:YES];
    // reset typing attribtues
    typedInput->textView.typingAttributes = typedInput->defaultTypingAttributes;
    return YES;
  }

  return NO;
}

@end