implement unicode emoji replacements

lib/pretty_text.rb

@@ -149,6 +149,7 @@ module PrettyText
       end
 
       if SiteSetting.enable_experimental_markdown_it
+        # defer load markdown it
         unless context.eval("window.markdownit")
           ctx_load_manifest(context, "markdown-it-bundle.js")
         end
@@ -168,6 +169,7 @@ module PrettyText
         __optInput.categoryHashtagLookup = __categoryLookup;
         __optInput.mentionLookup = __mentionLookup;
         __optInput.customEmoji = #{custom_emoji.to_json};
+        __optInput.emojiUnicodeReplacer = __emojiUnicodeReplacer;
       JS
 
       if opts[:topicId]

lib/pretty_text/shims.js

@@ -3,7 +3,28 @@ __buildOptions = require('pretty-text/pretty-text').buildOptions;
 __performEmojiUnescape = require('pretty-text/emoji').performEmojiUnescape;
 
 __utils = require('discourse/lib/utilities');
-__setUnicode = require('pretty-text/engines/discourse-markdown/emoji').setUnicodeReplacements;
+
+__emojiUnicodeReplacer = null;
+
+__setUnicode = function(replacements) {
+  require('pretty-text/engines/discourse-markdown/emoji').setUnicodeReplacements(replacements);
+  
+  let unicodeRegexp = new RegExp(Object.keys(replacements).sort().reverse().join("|"), "g");
+
+  __emojiUnicodeReplacer = function(text) {
+    unicodeRegexp.lastIndex = 0;
+    let m;
+    while ((m = unicodeRegexp.exec(text)) !== null) {
+      let replacement = ":" + replacements[m[0]] + ":";
+      const before = text.charAt(m.index-1);
+      if (!/\B/.test(before)) {
+        replacement = "\u200b" + replacement;
+      }
+      text = text.replace(m[0], replacement);
+    }
+    return text;
+  };
+};
 
 __paths = {};