Implement all emoji text message boosting

ElementX/Sources/Other/EmojiDetection.swift

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+//
+// Copyright 2023 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+
+extension UnicodeScalar {
+    var isZeroWidthJoiner: Bool {
+        value == 8205
+    }
+    
+    var isKeycap: Bool {
+        value == 8419
+    }
+    
+    var isNumber: Bool {
+        switch value {
+        case 48...57:
+            return true
+        default:
+            return false
+        }
+    }
+}
+
+extension String {
+    var containsOnlyEmoji: Bool {
+        guard !isEmpty else {
+            return false
+        }
+        
+        var emojiMarkerCount = 0
+        for scalar in unicodeScalars {
+            let isEmojiMarker = scalar.properties.isEmoji ||
+                scalar.properties.isEmojiPresentation ||
+                scalar.isZeroWidthJoiner ||
+                scalar.properties.isDefaultIgnorableCodePoint ||
+                scalar.isKeycap
+            
+            guard isEmojiMarker else {
+                return false
+            }
+            
+            emojiMarkerCount += 1
+        }
+        
+        // Plain numbers like 0 return true for .isEmoji. We don't want that
+        let markersRequiringSiblings = unicodeScalars.filter {
+            $0.properties.isEmoji && $0.isNumber
+        }
+        
+        return markersRequiringSiblings.count != emojiMarkerCount && emojiMarkerCount == unicodeScalars.count
+    }
+}