1 files changed, 120 insertions, 0 deletions
diff --git a/app/assets/javascripts/emoji/is_emoji_unicode_supported.js b/app/assets/javascripts/emoji/is_emoji_unicode_supported.js
new file mode 100644
index 00000000000..3fd23efa9f8
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+++ b/app/assets/javascripts/emoji/is_emoji_unicode_supported.js
@@ -0,0 +1,120 @@
+// On Windows, flags render as two-letter country codes, see http://emojipedia.org/flags/
+const flagACodePoint = 127462; // parseInt('1F1E6', 16)
+const flagZCodePoint = 127487; // parseInt('1F1FF', 16)
+function isFlagEmoji(emojiUnicode) {
+  const cp = emojiUnicode.codePointAt(0);
+  // Length 4 because flags are made of 2 characters which are surrogate pairs
+  return emojiUnicode.length === 4 && cp >= flagACodePoint && cp <= flagZCodePoint;
+}
+
+// Chrome <57 renders keycaps oddly
+// See https://bugs.chromium.org/p/chromium/issues/detail?id=632294
+// Same issue on Windows also fixed in Chrome 57, http://i.imgur.com/rQF7woO.png
+function isKeycapEmoji(emojiUnicode) {
+  return emojiUnicode.length === 3 && emojiUnicode[2] === '\u20E3';
+}
+
+// Check for a skin tone variation emoji which aren't always supported
+const tone1 = 127995;// parseInt('1F3FB', 16)
+const tone5 = 127999;// parseInt('1F3FF', 16)
+function isSkinToneComboEmoji(emojiUnicode) {
+  return emojiUnicode.length > 2 && Array.from(emojiUnicode).some((char) => {
+    const cp = char.codePointAt(0);
+    return cp >= tone1 && cp <= tone5;
+  });
+}
+
+// macOS supports most skin tone emoji's but
+// doesn't support the skin tone versions of horse racing
+const horseRacingCodePoint = 127943;// parseInt('1F3C7', 16)
+function isHorceRacingSkinToneComboEmoji(emojiUnicode) {
+  const firstCharacter = Array.from(emojiUnicode)[0];
+  return firstCharacter && firstCharacter.codePointAt(0) === horseRacingCodePoint &&
+    isSkinToneComboEmoji(emojiUnicode);
+}
+
+// Check for `family_*`, `kiss_*`, `couple_*`
+// For ex. Windows 8.1 Firefox 51.0.1, doesn't support these
+const zwj = 8205; // parseInt('200D', 16)
+const personStartCodePoint = 128102; // parseInt('1F466', 16)
+const personEndCodePoint = 128105; // parseInt('1F469', 16)
+function isPersonZwjEmoji(emojiUnicode) {
+  let hasPersonEmoji = false;
+  let hasZwj = false;
+  Array.from(emojiUnicode).forEach((character) => {
+    const cp = character.codePointAt(0);
+    if (cp === zwj) {
+      hasZwj = true;
+    } else if (cp >= personStartCodePoint && cp <= personEndCodePoint) {
+      hasPersonEmoji = true;
+    }
+  });
+
+  return hasPersonEmoji && hasZwj;
+}
+
+// Helper so we don't have to run `isFlagEmoji` twice
+// in `isEmojiUnicodeSupported` logic
+function checkFlagEmojiSupport(unicodeSupportMap, emojiUnicode) {
+  const isFlagResult = isFlagEmoji(emojiUnicode);
+  return (
+    (unicodeSupportMap.flag && isFlagResult) ||
+    !isFlagResult
+  );
+}
+
+// Helper so we don't have to run `isSkinToneComboEmoji` twice
+// in `isEmojiUnicodeSupported` logic
+function checkSkinToneModifierSupport(unicodeSupportMap, emojiUnicode) {
+  const isSkinToneResult = isSkinToneComboEmoji(emojiUnicode);
+  return (
+    (unicodeSupportMap.skinToneModifier && isSkinToneResult) ||
+    !isSkinToneResult
+  );
+}
+
+// Helper func so we don't have to run `isHorceRacingSkinToneComboEmoji` twice
+// in `isEmojiUnicodeSupported` logic
+function checkHorseRacingSkinToneComboEmojiSupport(unicodeSupportMap, emojiUnicode) {
+  const isHorseRacingSkinToneResult = isHorceRacingSkinToneComboEmoji(emojiUnicode);
+  return (
+    (unicodeSupportMap.horseRacing && isHorseRacingSkinToneResult) ||
+    !isHorseRacingSkinToneResult
+  );
+}
+
+// Helper so we don't have to run `isPersonZwjEmoji` twice
+// in `isEmojiUnicodeSupported` logic
+function checkPersonEmojiSupport(unicodeSupportMap, emojiUnicode) {
+  const isPersonZwjResult = isPersonZwjEmoji(emojiUnicode);
+  return (
+    (unicodeSupportMap.personZwj && isPersonZwjResult) ||
+    !isPersonZwjResult
+  );
+}
+
+// Takes in a support map and determines whether
+// the given unicode emoji is supported on the platform.
+//
+// Combines all the edge case tests into a one-stop shop method
+function isEmojiUnicodeSupported(unicodeSupportMap = {}, emojiUnicode, unicodeVersion) {
+  const isOlderThanChrome57 = unicodeSupportMap.meta && unicodeSupportMap.meta.isChrome &&
+    unicodeSupportMap.meta.chromeVersion < 57;
+
+  // For comments about each scenario, see the comments above each individual respective function
+  return unicodeSupportMap[unicodeVersion] &&
+    !(isOlderThanChrome57 && isKeycapEmoji(emojiUnicode)) &&
+    checkFlagEmojiSupport(unicodeSupportMap, emojiUnicode) &&
+    checkSkinToneModifierSupport(unicodeSupportMap, emojiUnicode) &&
+    checkHorseRacingSkinToneComboEmojiSupport(unicodeSupportMap, emojiUnicode) &&
+    checkPersonEmojiSupport(unicodeSupportMap, emojiUnicode);
+}
+
+export {
+  isEmojiUnicodeSupported as default,
+  isFlagEmoji,
+  isKeycapEmoji,
+  isSkinToneComboEmoji,
+  isHorceRacingSkinToneComboEmoji,
+  isPersonZwjEmoji,
+};