Add rudimentary JavaScript highlighting to query text view

MongoView/Synax Highlighting/JavaScriptHighlighter.swift

@@ -38,14 +38,7 @@ class JavaScriptHighlighter {
         return NSRange(from..<to, in: text)
     }
     
-    private func prevCharRange() -> NSRange {
+    private func peek() -> Unicode.Scalar {
-        return range(from: text.index(before: currentIndex), to: currentIndex)
-    }
-    
-    private func peek() -> Unicode.Scalar? {
-        guard currentIndex < text.endIndex else {
-            return nil
-        }
         return text.unicodeScalars[currentIndex]
     }
     
@@ -55,7 +48,7 @@ class JavaScriptHighlighter {
     }
     
     @discardableResult
-    private func consume() -> Unicode.Scalar? {
+    private func consume() -> Unicode.Scalar {
         let c = peek()
         currentIndex = text.index(after: currentIndex)
         return c
@@ -79,7 +72,7 @@ class JavaScriptHighlighter {
     }
 
     private func consumeExpression() {
-        guard let char = peek() else { return }
+        let char = peek()
         
         if identifierStarts.contains(char) {
             consumeIdentifier()
@@ -106,7 +99,7 @@ class JavaScriptHighlighter {
 
     private func consumeIdentifier() {
         let identifierStart = currentIndex!
-        while let char = peek(), identifiers.contains(char) {
+        while currentIndex < text.endIndex && identifiers.contains(peek()) {
             consume()
         }
         print("Identifier: '\(text[identifierStart..<currentIndex])'")
@@ -114,12 +107,12 @@ class JavaScriptHighlighter {
 
     private func consumeNumber() {
         let numberStart = currentIndex!
-        while let char = peek(), CharacterSet.decimalDigits.contains(char) {
+        while currentIndex < text.endIndex && CharacterSet.decimalDigits.contains(peek()) {
             consume()
         }
         if currentIndex < text.endIndex && peek() == "." {
             consume()
-            while let char = peek(), CharacterSet.decimalDigits.contains(char) {
+            while currentIndex < text.endIndex && CharacterSet.decimalDigits.contains(peek()) {
                 consume()
             }
         }
@@ -180,14 +173,14 @@ class JavaScriptHighlighter {
     }
 
     private func consumeOperator() {
-        print("Operator: \(peek()!)")
+        print("Operator: \(peek())")
         consume()
     }
     
     private func consumeFunctionCallOrGrouping() {
         consume() // (
         print("Opening (")
-        attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: prevCharRange())
+        attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: range(from: text.index(before: currentIndex), to: currentIndex))
         indent += "  "
         while currentIndex < text.endIndex && peek() != ")" {
             consumeExpression()
@@ -196,14 +189,14 @@ class JavaScriptHighlighter {
         if currentIndex < text.endIndex {
             consume() // )
             print("Closing )")
-            attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: prevCharRange())
+            attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: range(from: text.index(before: currentIndex), to: currentIndex))
         }
     }
     
     private func consumeObject() {
         consume() // {
         print("Opening {")
-        attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: prevCharRange())
+        attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: range(from: text.index(before: currentIndex), to: currentIndex))
         indent += "  "
         object:
         while currentIndex < text.endIndex && peek() != "}" {
@@ -226,13 +219,13 @@ class JavaScriptHighlighter {
         if currentIndex < text.endIndex {
             consume() // }
             print("Closing }")
-            attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: prevCharRange())
+            attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: range(from: text.index(before: currentIndex), to: currentIndex))
         }
     }
     
     private func consumeObjectKey() {
         let keyStart = currentIndex!
-        while let char = peek(), identifiers.contains(char) {
+        while currentIndex < text.endIndex && identifiers.contains(peek()) {
             consume()
         }
         print("Object key: '\(text[keyStart..<currentIndex])'")
@@ -241,13 +234,13 @@ class JavaScriptHighlighter {
     private func consumeDotLookup() {
         consume() // .
         print("Dot lookup")
-        attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: prevCharRange())
+        attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: range(from: text.index(before: currentIndex), to: currentIndex))
     }
     
     private func consumeArray() {
         consume() // [
         print("Opening [")
-        attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: prevCharRange())
+        attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: range(from: text.index(before: currentIndex), to: currentIndex))
         indent += "  "
         array:
         while currentIndex < text.endIndex && peek() != "]" {
@@ -269,7 +262,7 @@ class JavaScriptHighlighter {
         if currentIndex < text.endIndex {
             consume() // ]
             print("Closing ]")
-            attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: prevCharRange())
+            attributed.addAttribute(.foregroundColor, value: NSColor.systemTeal, range: range(from: text.index(before: currentIndex), to: currentIndex))
         }
     }