1 files changed, 79 insertions, 0 deletions
diff --git a/lib/private/EmojiHelper.php b/lib/private/EmojiHelper.php
new file mode 100644
index 00000000000..52ab441e73a
--- /dev/null
+++ b/lib/private/EmojiHelper.php
@@ -0,0 +1,79 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2020 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OC;
+
+use OCP\IDBConnection;
+use OCP\IEmojiHelper;
+
+class EmojiHelper implements IEmojiHelper {
+	private IDBConnection $db;
+
+	public function __construct(IDBConnection $db) {
+		$this->db = $db;
+	}
+
+	public function doesPlatformSupportEmoji(): bool {
+		return $this->db->supports4ByteText()
+			&& \class_exists(\IntlBreakIterator::class);
+	}
+
+	public function isValidSingleEmoji(string $emoji): bool {
+		$intlBreakIterator = \IntlBreakIterator::createCharacterInstance();
+		$intlBreakIterator->setText($emoji);
+
+		$characterCount = 0;
+		while ($intlBreakIterator->next() !== \IntlBreakIterator::DONE) {
+			$characterCount++;
+		}
+
+		if ($characterCount !== 1) {
+			return false;
+		}
+
+		$codePointIterator = \IntlBreakIterator::createCodePointInstance();
+		$codePointIterator->setText($emoji);
+
+		foreach ($codePointIterator->getPartsIterator() as $codePoint) {
+			$codePointType = \IntlChar::charType($codePoint);
+
+			// Unicode chars need 2 or more chars
+			// The characterCount before this loop already validate if is a single emoji
+			// This condition is to don't continue if non emoji chars
+			if (strlen($emoji) >= 2) {
+				// If the current code-point is an emoji or a modifier (like a skin-tone)
+				// just continue and check the next character
+				if ($codePointType === \IntlChar::CHAR_CATEGORY_MODIFIER_SYMBOL
+					|| $codePointType === \IntlChar::CHAR_CATEGORY_MODIFIER_LETTER
+					|| $codePointType === \IntlChar::CHAR_CATEGORY_OTHER_SYMBOL
+					|| $codePointType === \IntlChar::CHAR_CATEGORY_FORMAT_CHAR          // i.e. 🏴󠁧󠁢󠁥󠁮󠁧󠁿 🏴󠁧󠁢󠁳󠁣󠁴󠁿
+					|| $codePointType === \IntlChar::CHAR_CATEGORY_OTHER_PUNCTUATION    // i.e. ‼️ ⁉️ #⃣
+					|| $codePointType === \IntlChar::CHAR_CATEGORY_LOWERCASE_LETTER     // i.e. ℹ️
+					|| $codePointType === \IntlChar::CHAR_CATEGORY_MATH_SYMBOL          // i.e. ↔️ ◻️ ⤴️ ⤵️
+					|| $codePointType === \IntlChar::CHAR_CATEGORY_ENCLOSING_MARK       // i.e. 0⃣..9⃣
+					|| $codePointType === \IntlChar::CHAR_CATEGORY_DECIMAL_DIGIT_NUMBER // i.e. 0⃣..9⃣
+					|| $codePointType === \IntlChar::CHAR_CATEGORY_DASH_PUNCTUATION     // i.e. 〰️
+					|| $codePointType === \IntlChar::CHAR_CATEGORY_GENERAL_OTHER_TYPES
+				) {
+					continue;
+				}
+			}
+
+			// If it's neither a modifier nor an emoji, we only allow
+			// a zero-width-joiner or a variation selector 16
+			$codePointValue = \IntlChar::ord($codePoint);
+			if ($codePointValue === 8205 || $codePointValue === 65039) {
+				continue;
+			}
+
+			return false;
+		}
+
+		return true;
+	}
+}