[ASTextNode2] Add initial implementation for link handling. (#396)

* [ASTextNode2] Add initial implementation for link handling.

This is a fairly basic first step to achieving feature parity between ASTextNode2
and ASTextNode. It does not yet do the 9-box detection of links, and there is
other code from ASTextNode that could be shared to improve this.

However, in the interest of getting a shippable implementation running as soon
as possible, I'm hoping to quickly refine this. Then we can continue improving
it based on the original ASTextNode with the benefit of testing UI against it.

* [ASTextNode2] Refine implementation of link handling.

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## master
 
 * Add your own contributions to the next release on the line below this with your name.
+- [ASTextNode2] Add initial implementation for link handling. [Scott Goodson](https://github.com/appleguy) [#396](https://github.com/TextureGroup/Texture/pull/396)
 
 ##2.3.4
 - [Yoga] Rewrite YOGA_TREE_CONTIGUOUS mode with improved behavior and cleaner integration [Scott Goodson](https://github.com/appleguy)

Source/Private/ASTextNode2.mm

@@ -488,7 +488,52 @@ static NSArray *DefaultLinkAttributeNames = @[ NSLinkAttributeName ];
    inAdditionalTruncationMessage:(out BOOL *)inAdditionalTruncationMessageOut
                  forHighlighting:(BOOL)highlighting
 {
-  AS_TEXT_ALERT_UNIMPLEMENTED_FEATURE();
+  ASDN::MutexLocker l(__instanceLock__);
+
+  // TODO: The copy and application of size shouldn't be required, but it is currently.
+  // See discussion in https://github.com/TextureGroup/Texture/pull/396
+  ASTextContainer *containerCopy = [_textContainer copy];
+  containerCopy.size = self.calculatedSize;
+  ASTextLayout *layout = [ASTextNode2 compatibleLayoutWithContainer:containerCopy text:_attributedText];
+  NSRange visibleRange = layout.visibleRange;
+  NSRange clampedRange = NSIntersectionRange(visibleRange, NSMakeRange(0, _attributedText.length));
+
+  ASTextRange *range = [layout closestTextRangeAtPoint:point];
+
+  // For now, assume that a tap inside this text, but outside the text range is a tap on the
+  // truncation token.
+  if (![layout textRangeAtPoint:point]) {
+    *inAdditionalTruncationMessageOut = YES;
+    return nil;
+  }
+
+  NSRange effectiveRange = NSMakeRange(0, 0);
+  for (__strong NSString *attributeName in self.linkAttributeNames) {
+    id value = [self.attributedText attribute:attributeName atIndex:range.start.offset longestEffectiveRange:&effectiveRange inRange:clampedRange];
+    if (value == nil) {
+      // Didn't find any links specified with this attribute.
+      continue;
+    }
+
+    // If highlighting, check with delegate first. If not implemented, assume YES.
+    if (highlighting
+        && [_delegate respondsToSelector:@selector(textNode:shouldHighlightLinkAttribute:value:atPoint:)]
+        && ![_delegate textNode:(ASTextNode *)self shouldHighlightLinkAttribute:attributeName value:value atPoint:point]) {
+      value = nil;
+      attributeName = nil;
+    }
+
+    if (value != nil || attributeName != nil) {
+      *rangeOut = NSIntersectionRange(visibleRange, effectiveRange);
+
+      if (attributeNameOut != NULL) {
+        *attributeNameOut = attributeName;
+      }
+
+      return value;
+    }
+  }
+
   return nil;
 }
 
@@ -560,8 +605,13 @@ static NSArray *DefaultLinkAttributeNames = @[ NSLinkAttributeName ];
 
 - (void)_setHighlightRange:(NSRange)highlightRange forAttributeName:(NSString *)highlightedAttributeName value:(id)highlightedAttributeValue animated:(BOOL)animated
 {
+  // Set these so that link tapping works.
+  _highlightedLinkAttributeName = highlightedAttributeName;
+  _highlightedLinkAttributeValue = highlightedAttributeValue;
+
   AS_TEXT_ALERT_UNIMPLEMENTED_FEATURE();
   // Much of the code from original ASTextNode is probably usable here.
+
   return;
 }
 
@@ -665,7 +715,39 @@ static NSArray *DefaultLinkAttributeNames = @[ NSLinkAttributeName ];
   ASDisplayNodeAssertMainThread();
 
   [super touchesBegan:touches withEvent:event];
-  AS_TEXT_ALERT_UNIMPLEMENTED_FEATURE();
+
+  CGPoint point = [[touches anyObject] locationInView:self.view];
+
+  NSRange range = NSMakeRange(0, 0);
+  NSString *linkAttributeName = nil;
+  BOOL inAdditionalTruncationMessage = NO;
+
+  id linkAttributeValue = [self _linkAttributeValueAtPoint:point
+                                             attributeName:&linkAttributeName
+                                                     range:&range
+                             inAdditionalTruncationMessage:&inAdditionalTruncationMessage
+                                           forHighlighting:YES];
+
+  NSUInteger lastCharIndex = NSIntegerMax;
+  BOOL linkCrossesVisibleRange = (lastCharIndex > range.location) && (lastCharIndex < NSMaxRange(range) - 1);
+
+  if (inAdditionalTruncationMessage) {
+    NSRange visibleRange = NSMakeRange(0, 0);
+    {
+      ASDN::MutexLocker l(__instanceLock__);
+      // TODO: The copy and application of size shouldn't be required, but it is currently.
+      // See discussion in https://github.com/TextureGroup/Texture/pull/396
+      ASTextContainer *containerCopy = [_textContainer copy];
+      containerCopy.size = self.calculatedSize;
+      ASTextLayout *layout = [ASTextNode2 compatibleLayoutWithContainer:containerCopy text:_attributedText];
+      visibleRange = layout.visibleRange;
+    }
+    NSRange truncationMessageRange = [self _additionalTruncationMessageRangeWithVisibleRange:visibleRange];
+    [self _setHighlightRange:truncationMessageRange forAttributeName:ASTextNodeTruncationTokenAttributeName value:nil animated:YES];
+  } else if (range.length && !linkCrossesVisibleRange && linkAttributeValue != nil && linkAttributeName != nil) {
+    [self _setHighlightRange:range forAttributeName:linkAttributeName value:linkAttributeValue animated:YES];
+  }
+
   return;
 }