Added misc helper functions (#235)

Author: rajdeep

Diff for: Proton/Sources/Swift/Editor/EditorView.swift

@@ -152,6 +152,11 @@ open class EditorView: UIView {
     /// mat be more than when synchronous mode, ie default, is used. The perceived performance/TTI will almost always be better with asynchronous rendering.
     public weak var asyncAttachmentRenderingDelegate: AsyncAttachmentRenderingDelegate?
 
+    /// Returns `UITextInput` of current instance
+    public var textInput: UITextInput {
+        richTextView
+    }
+
     public var textInteractions: [UITextInteraction] {
         richTextView.interactions.compactMap({ $0 as? UITextInteraction })
     }
@@ -740,6 +745,18 @@ open class EditorView: UIView {
         return richTextView.becomeFirstResponder()
     }
 
+    /// Denotes of the Editor is first responder
+    /// - Returns: true, if is first responder
+    public func isFirstResponder() -> Bool {
+        richTextView.isFirstResponder
+    }
+
+    /// Resets typing attributes back to default text color, font and paragraph style.
+    ///All other attributes are dropped.
+    public func resetTypingAttributes() {
+        richTextView.resetTypingAttributes()
+    }
+
     /// Converts given range to `UITextRange`, if valid
     /// - Parameter range: Range to convert
     /// - Returns: `UITextRange` representation of provided NSRange, if valid.

Diff for: Proton/Sources/Swift/Helpers/NSRangeExtensions.swift

@@ -33,7 +33,11 @@ public extension NSRange {
     }
 
     var lastCharacterRange: NSRange {
-        return NSRange(location: location + length, length: 1)
+        return NSRange(location: max(location + length - 1, 0), length: 1)
+    }
+
+    var previousPosition: NSRange {
+        return NSRange(location: max(location - 1, 0), length: 0)
     }
 
     var nextPosition: NSRange {
@@ -44,6 +48,14 @@ public extension NSRange {
         return location + length
     }
 
+    var nextCharacterRange: NSRange {
+        NSRange(location: location + length, length: 1)
+    }
+
+    var previousCharacterRange: NSRange {
+        NSRange(location: location - 1, length: 1)
+    }
+
     /// Converts the range to `UITextRange` in given `UITextInput`. Returns nil if the range is invalid in the `UITextInput`.
     /// - Parameter textInput: UITextInput to convert the range in.
     func toTextRange(textInput: UITextInput) -> UITextRange? {