Prevent string manipulation in the utf-16 view

Author: intitni

Core/Sources/Service/SuggestionCommandHandler/WindowBaseCommandHandler.swift

@@ -375,19 +375,11 @@ extension WindowBaseCommandHandler {
                 guard selection.start.character > 0,
                       selection.start.character < line.utf16.count
                 else { return false }
-                let substring = String(
-                    line.utf16[line.utf16.startIndex..<(line.index(
-                        line.utf16.startIndex,
-                        offsetBy: selection.start.character,
-                        limitedBy: line.utf16.endIndex
-                    ) ?? line.utf16.endIndex)]
-                ) ?? String(
-                    line[line.startIndex..<(line.index(
-                        line.startIndex,
-                        offsetBy: selection.start.character,
-                        limitedBy: line.endIndex
-                    ) ?? line.endIndex)]
-                )
+                let substring = line[line.utf16.startIndex..<(line.index(
+                    line.utf16.startIndex,
+                    offsetBy: selection.start.character,
+                    limitedBy: line.utf16.endIndex
+                ) ?? line.utf16.endIndex)]
                 return substring.allSatisfy { $0.isWhitespace }
             }()
 

Tool/Sources/SuggestionModel/EditorInformation.swift

@@ -107,18 +107,30 @@ public struct EditorInformation {
         }
         var content = rangeLines
         if !content.isEmpty {
-            let dropLastCount = max(
-                0,
-                content[content.endIndex - 1].utf16.count - range.end.character
-            )
-            content[content.endIndex - 1] = String(
-                content[content.endIndex - 1].utf16.dropLast(dropLastCount)
-            ) ?? String(
-                content[content.endIndex - 1].dropLast(dropLastCount)
-            )
-            let dropFirstCount = max(0, range.start.character)
-            content[0] = String(content[0].utf16.dropFirst(dropFirstCount))
-                ?? String(content[0].dropFirst(dropFirstCount))
+            let lastLine = content[content.endIndex - 1]
+            let droppedEndIndex = lastLine.utf16.index(
+                lastLine.utf16.startIndex,
+                offsetBy: range.end.character,
+                limitedBy: lastLine.utf16.endIndex
+            ) ?? lastLine.utf16.endIndex
+            content[content.endIndex - 1] = if droppedEndIndex > lastLine.utf16.startIndex {
+                String(lastLine[..<droppedEndIndex])
+            } else {
+                ""
+            }
+            
+            let firstLine = content[0]
+            let droppedStartIndex = firstLine.utf16.index(
+                firstLine.utf16.startIndex,
+                offsetBy: range.start.character,
+                limitedBy: firstLine.utf16.endIndex
+            ) ?? firstLine.utf16.endIndex
+            
+            content[0] = if droppedStartIndex < firstLine.utf16.endIndex {
+                String(firstLine[droppedStartIndex...])
+            } else {
+                ""
+            }
         }
         return (content.joined(), rangeLines)
     }

Tool/Sources/WorkspaceSuggestionService/Filespace+SuggestionService.swift

@@ -82,22 +82,22 @@ public extension Filespace {
                 "Generating suggestion with invalid range"
             )
 
-            let uff16View = editingLine.utf16
+            let utf16View = editingLine.utf16
 
-            let startIndex = uff16View.index(
-                uff16View.startIndex,
+            let startIndex = utf16View.index(
+                utf16View.startIndex,
                 offsetBy: max(0, presentingSuggestion.range.start.character),
-                limitedBy: uff16View.endIndex
-            ) ?? uff16View.startIndex
+                limitedBy: utf16View.endIndex
+            ) ?? utf16View.startIndex
 
-            let endIndex = uff16View.index(
-                uff16View.startIndex,
+            let endIndex = utf16View.index(
+                utf16View.startIndex,
                 offsetBy: cursorPosition.character,
-                limitedBy: uff16View.endIndex
-            ) ?? uff16View.endIndex
+                limitedBy: utf16View.endIndex
+            ) ?? utf16View.endIndex
 
             if endIndex > startIndex {
-                return String(uff16View[startIndex..<endIndex]) ?? ""
+                return String(editingLine[startIndex..<endIndex])
             }
 
             return ""