feat: make iOS mentions work with a single space (#289)

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# Summary

This PR makes iOS mentions tolerate a single space. 
Code responsible for detecting a currently edited mention would just
take the current word into the account.
Now it works by trying to search for one more word before the current
one if needed. This way all of the following scenarios will be detected
as editable mention:
- current word with a mention indicator
- a space character, but previous word has a mention indicator
- current word with no mention indicator but previous word has one

Effectively these scenarios are enough to achieve space tolerating
mentions.

## Test Plan

Open iOS example app and play with mentions and spaces.

## Screenshots / Videos


https://github.com/user-attachments/assets/80b53b4d-509a-4d43-8a33-53e911e27132

## Compatibility

| OS      | Implemented |
| ------- | :---------: |
| iOS     |    ✅     |
| Android |    ❌     |

Author: szydlovsky

ios/EnrichedTextInputView.mm

@@ -1035,7 +1035,12 @@ - (void)manageSelectionBasedChanges {
   MentionStyle *mentionStyleClass = (MentionStyle *)stylesDict[@([MentionStyle getStyleType])];
   if(mentionStyleClass != nullptr) {
     [mentionStyleClass manageMentionTypingAttributes];
-    [mentionStyleClass manageMentionEditing];
+    
+    // mention editing runs if only a selection was done (no text change)
+    // otherwise we would double-emit with a second call in the anyTextMayHaveBeenModified method
+    if([_recentlyEmittedString isEqualToString:[textView.textStorage.string copy]]) {
+      [mentionStyleClass manageMentionEditing];
+    }
   }
 
   // typing attributes for empty lines selection reset
@@ -1112,10 +1117,11 @@ - (void)anyTextMayHaveBeenModified {
     [h3Style handleImproperHeadings];
   }
 
-  // mentions removal management
+  // mentions management: removal and editing
   MentionStyle *mentionStyleClass = (MentionStyle *)stylesDict[@([MentionStyle getStyleType])];
   if(mentionStyleClass != nullptr) {
     [mentionStyleClass handleExistingMentions];
+    [mentionStyleClass manageMentionEditing];
   }
 
   // placholder management

ios/styles/MentionStyle.mm

@@ -299,45 +299,24 @@ - (void)manageMentionEditing {
     return;
   }
 
-  // get the current word if it exists
-  // we can be using current word only thanks to the fact that ongoing mentions are always one word (in contrast to ready, added mentions)
-  NSDictionary *currentWord = [WordsUtils getCurrentWord:_input->textView.textStorage.string range:_input->textView.selectedRange];
-  if(currentWord == nullptr) {
+  // get the text (and its range) that could be an editable mention
+  NSArray *mentionCandidate = [self getMentionCandidate];
+  if(mentionCandidate == nullptr) {
     [self removeActiveMentionRange];
     return;
   }
+  NSString *candidateText = mentionCandidate[0];
+  NSRange candidateRange = [(NSValue *)mentionCandidate[1] rangeValue];
 
-  // get word properties
-  NSString *wordText = (NSString *)[currentWord objectForKey:@"word"];
-  NSValue *wordRangeValue = (NSValue *)[currentWord objectForKey:@"range"];
-  if(wordText == nullptr || wordRangeValue == nullptr) {
-    [self removeActiveMentionRange];
-    return;
-  }
-  NSRange wordRange = [wordRangeValue rangeValue];
-  
-  // check for mentionIndicators - no sign of them means we shouldn't be editing a mention
-  unichar firstChar = [wordText characterAtIndex:0];
-  if(![[_input->config mentionIndicators] containsObject: @(firstChar)]) {
-    [self removeActiveMentionRange];
-    return;
-  }
-  
-  // check for existing mentions - we don't edit them
-  if([self detectStyle:wordRange]) {
-    [self removeActiveMentionRange];
-    return;
-  }
-  
-  // get style classes that the mention shouldn't be recognized in
+  // get style classes that the mention shouldn't be recognized in, together with other mentions
   NSArray *conflicts = _input->conflictingStyles[@([MentionStyle getStyleType])];
   NSArray *blocks = _input->blockingStyles[@([MentionStyle getStyleType])];
-  NSArray *allConflicts = [conflicts arrayByAddingObjectsFromArray:blocks];
+  NSArray *allConflicts = [[conflicts arrayByAddingObjectsFromArray:blocks] arrayByAddingObject:@([MentionStyle getStyleType])];
   BOOL conflictingStyle = NO;
 
   for(NSNumber *styleType in allConflicts) {
     id<BaseStyleProtocol> styleClass = _input->stylesDict[styleType];
-    if(styleClass != nullptr && [styleClass anyOccurence:wordRange]) {
+    if(styleClass != nullptr && [styleClass anyOccurence:candidateRange]) {
       conflictingStyle = YES;
       break;
     }
@@ -350,7 +329,7 @@ - (void)manageMentionEditing {
   }
 
   // everything checks out - we are indeed editing a mention
-  [self setActiveMentionRange:wordRange text:wordText];
+  [self setActiveMentionRange:candidateRange text:candidateText];
 }
 
 // used to fix mentions' typing attributes
@@ -462,6 +441,116 @@ - (MentionStyleProps *)stylePropsWithParams:(MentionParams *)params {
   return [_input->config mentionStylePropsForIndicator:params.indicator];
 }
 
+// finds if any word/words around current selection are eligible to be edited as mentions
+// since we allow for a single space inside an edited mention, we have take both current and the previous word into account
+- (NSArray *)getMentionCandidate {
+  NSDictionary *currentWord, *previousWord;
+  NSString *currentWordText, *previousWordText, *finalText;
+  NSValue *currentWordRange, *previousWordRange;
+  NSRange finalRange;
+  
+  // word at the current selection
+  currentWord = [WordsUtils getCurrentWord:_input->textView.textStorage.string range:_input->textView.selectedRange];
+  if(currentWord != nullptr ) {
+    currentWordText = (NSString *)[currentWord objectForKey:@"word"];
+    currentWordRange = (NSValue *)[currentWord objectForKey:@"range"];
+  }
+    
+  if(currentWord != nullptr) {
+    // current word exists
+    unichar currentFirstChar = [currentWordText characterAtIndex:0];
+    
+    if([[_input->config mentionIndicators] containsObject:@(currentFirstChar)]) {
+      // current word exists and has a mention indicator; no need to check for the previous word
+      finalText = currentWordText;
+      finalRange = [currentWordRange rangeValue];
+    } else {
+      // current word exists but no traces of mention indicator; get the previous word
+      
+      NSInteger previousWordSearchLocation = [currentWordRange rangeValue].location - 1;
+      if(previousWordSearchLocation < 0) {
+        // previous word can't exist
+        return nullptr;
+      }
+      
+      unichar separatorChar = [_input->textView.textStorage.string characterAtIndex:previousWordSearchLocation];
+      if(![[NSCharacterSet whitespaceCharacterSet] characterIsMember:separatorChar]) {
+        // we want to check for the previous word ONLY if the separating character was a space
+        // newlines don't make it
+        return nullptr;
+      }
+      
+      previousWord = [WordsUtils getCurrentWord:_input->textView.textStorage.string range:NSMakeRange(previousWordSearchLocation, 0)];
+      
+      if(previousWord != nullptr) {
+        // previous word exists; get its properties
+        previousWordText = (NSString *)[previousWord objectForKey:@"word"];
+        previousWordRange = (NSValue *)[previousWord objectForKey:@"range"];
+      
+        // check for the mention indicators in the previous word
+        unichar previousFirstChar = [previousWordText characterAtIndex:0];
+        
+        if([[_input->config mentionIndicators] containsObject:@(previousFirstChar) ]) {
+          // previous word has a proper mention indicator: treat both words as an editable mention
+          finalText = [NSString stringWithFormat:@"%@ %@", previousWordText, currentWordText];
+          // range length is both words' lengths + 1 for a space between them
+          finalRange = NSMakeRange(
+            [previousWordRange rangeValue].location,
+            [previousWordRange rangeValue].length + [currentWordRange rangeValue].length + 1
+          );
+        } else {
+          // neither current nor previous words have a mention indicator
+          return nullptr;
+        }
+      } else {
+        // previous word doesn't exist and no mention indicators in the current word
+        return nullptr;
+      }
+    }
+  } else {
+    // current word doesn't exist; try getting the previous one
+    
+    NSInteger previousWordSearchLocation = _input->textView.selectedRange.location - 1;
+    if(previousWordSearchLocation < 0) {
+      // previous word can't exist
+      return nullptr;
+    }
+    
+    unichar separatorChar = [_input->textView.textStorage.string characterAtIndex:previousWordSearchLocation];
+    if(![[NSCharacterSet whitespaceCharacterSet] characterIsMember:separatorChar]) {
+      // we want to check for the previous word ONLY if the separating character was a space
+      // newlines don't make it
+      return nullptr;
+    }
+    
+    previousWord = [WordsUtils getCurrentWord:_input->textView.textStorage.string range:NSMakeRange(previousWordSearchLocation, 0)];
+      
+    if(previousWord != nullptr) {
+      // previous word exists; get its properties
+      previousWordText = (NSString *)[previousWord objectForKey:@"word"];
+      previousWordRange = (NSValue *)[previousWord objectForKey:@"range"];
+      
+      // check for the mention indicators in the previous word
+      unichar previousFirstChar = [previousWordText characterAtIndex:0];
+      
+      if([[_input->config mentionIndicators] containsObject:@(previousFirstChar)]) {
+        // previous word has a proper mention indicator; treat previous word + a space as a editable mention
+        finalText = [NSString stringWithFormat:@"%@ ", previousWordText];
+        // the range length is previous word length + 1 for a space
+        finalRange = NSMakeRange([previousWordRange rangeValue].location, [previousWordRange rangeValue].length + 1);
+      } else {
+        // no current word, previous has no mention indicators
+        return nullptr;
+      }
+    } else {
+      // no current word, no previous word
+      return nullptr;
+    }
+  }
+  
+  return @[finalText, [NSValue valueWithRange:finalRange]];
+}
+
 // both used for setting the active mention range + indicator and fires proper onMention event
 - (void)setActiveMentionRange:(NSRange)range text:(NSString *)text {
   NSString *indicatorString = [NSString stringWithFormat:@"%C", [text characterAtIndex:0]];