Added SwiftUITextOutputFormat to output a Text struct

Sources/Splash/Output/AttributedStringOutputFormat.swift

@@ -5,6 +5,7 @@
  */
 
 #if !os(Linux)
+#if canImport(SwiftUI)
 
 import Foundation
 
@@ -65,3 +66,4 @@ private extension NSMutableAttributedString {
 }
 
 #endif
+#endif

Sources/Splash/Output/SwiftUITextOutputFormat.swift

@@ -0,0 +1,81 @@
+//
+//  SwiftUITextOutputFormat.swift
+//
+//  Created by Andrew Eades on 02/01/2020.
+//  Copyright © 2020 Andrew Eades. All rights reserved.
+//
+
+
+#if !os(Linux)
+#if canImport(SwiftUI)
+
+import SwiftUI
+
+import Foundation
+
+/// Output format to use to generate an NSAttributedString from the
+/// highlighted code. A `Theme` is used to determine what fonts and
+/// colors to use for the various tokens.
+public struct SwiftUITextOutputFormat: OutputFormat {
+    public var theme: Theme
+
+    public init(theme: Theme) {
+        self.theme = theme
+    }
+
+    public func makeBuilder() -> Builder {
+        return Builder(theme: theme)
+    }
+}
+
+public extension SwiftUITextOutputFormat {
+    struct Builder: OutputBuilder {
+        private let theme: Theme
+        private var texts = [Text]()
+
+        fileprivate init(theme: Theme) {
+            self.theme = theme
+        }
+
+        public mutating func addToken(_ token: String, ofType type: TokenType) {
+            let tokenColor = swiftUIColor(forType: type)
+
+            texts.append(Text(token).foregroundColor(tokenColor))
+        }
+
+        public mutating func addPlainText(_ plainText: String) {
+            let tokenColor = SwiftUI.Color(theme.plainTextColor)
+
+            texts.append(Text(plainText).foregroundColor(tokenColor))
+        }
+
+        public mutating func addWhitespace(_ whitespace: String) {
+            let tokenColor = SwiftUI.Color.white
+
+            texts.append(Text(whitespace).foregroundColor(tokenColor))
+        }
+
+        public func build() -> Text {
+
+            let highlightedText = texts.reduce(Text(""), +)
+
+            return highlightedText
+        }
+
+        private func swiftUIColor(forType type: TokenType) -> SwiftUI.Color {
+            var tokenColor: SwiftUI.Color
+
+            if let color = theme.tokenColors[type] {
+                tokenColor = SwiftUI.Color(color)
+            } else {
+                tokenColor = SwiftUI.Color.white
+            }
+
+            return tokenColor
+        }
+
+    }
+}
+
+#endif
+#endif