Add syntax highlighter

app/src/main/java/com/annimon/hotarufx/Main.java

@@ -1,5 +1,6 @@
 package com.annimon.hotarufx;
 
+import com.annimon.hotarufx.ui.controller.EditorController;
 import java.io.IOException;
 import javafx.application.Application;
 import javafx.fxml.FXMLLoader;
@@ -9,12 +10,15 @@ import lombok.val;
 
 public class Main extends Application {
 
+    private EditorController controller;
+
     @Override
     public void start(Stage primaryStage) {
         primaryStage.setTitle("HotaruFX");
         try {
             val loader = new FXMLLoader(getClass().getResource("/fxml/Editor.fxml"));
             val scene = new Scene(loader.load());
+            controller = loader.getController();
             primaryStage.setScene(scene);
         } catch (IOException e) {
             // TODO: notice me!!
@@ -22,6 +26,14 @@ public class Main extends Application {
         primaryStage.show();
     }
 
+    @Override
+    public void stop() throws Exception {
+        if (controller != null) {
+            controller.stop();
+        }
+        super.stop();
+    }
+
     public static void main(String[] args) {
         launch(args);
     }

app/src/main/java/com/annimon/hotarufx/ui/SyntaxHighlighter.java

@@ -0,0 +1,63 @@
+package com.annimon.hotarufx.ui;
+
+import com.annimon.hotarufx.lexer.HotaruLexer;
+import java.time.Duration;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Optional;
+import java.util.concurrent.ExecutorService;
+import javafx.concurrent.Task;
+import lombok.RequiredArgsConstructor;
+import lombok.val;
+import org.fxmisc.richtext.CodeArea;
+import org.fxmisc.richtext.StyleSpans;
+import org.fxmisc.richtext.StyleSpansBuilder;
+
+@RequiredArgsConstructor
+public class SyntaxHighlighter {
+
+    private final CodeArea editor;
+    private final ExecutorService executor;
+
+    public void init() {
+        editor.richChanges()
+                .filter(ch -> !ch.getInserted().equals(ch.getRemoved()))
+                .successionEnds(Duration.ofMillis(500))
+                .supplyTask(this::computeHighlightingAsync)
+                .awaitLatest(editor.richChanges())
+                .filterMap(t -> Optional.ofNullable(t.isSuccess() ? t.get() : null))
+                .subscribe(spans -> editor.setStyleSpans(0, spans));
+    }
+
+    public void release() {
+        executor.shutdown();
+    }
+
+    private Task<StyleSpans<Collection<String>>> computeHighlightingAsync() {
+        val text = editor.getText();
+        val task = new Task<StyleSpans<Collection<String>>>() {
+            @Override
+            protected StyleSpans<Collection<String>> call() throws Exception {
+                val spans = new StyleSpansBuilder<Collection<String>>();
+                for (val t : new HotaruLexer(text).tokenize()) {
+                    val category = t.getType().getPrimaryCategory();
+                    switch (category) {
+                        case "string":
+                        case "keyword":
+                        case "comment":
+                        case "number":
+                            spans.add(Collections.singleton(category), t.getLength());
+                            break;
+
+                        default:
+                            spans.add(Collections.emptyList(), t.getLength());
+                            break;
+                    }
+                }
+                return spans.create();
+            }
+        };
+        executor.execute(task);
+        return task;
+    }
+}

app/src/main/java/com/annimon/hotarufx/ui/controller/EditorController.java

@@ -9,13 +9,14 @@ import com.annimon.hotarufx.lib.Context;
 import com.annimon.hotarufx.parser.HotaruParser;
 import com.annimon.hotarufx.parser.ParseError;
 import com.annimon.hotarufx.parser.visitors.InterpreterVisitor;
+import com.annimon.hotarufx.ui.SyntaxHighlighter;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URL;
-import java.time.Duration;
 import java.util.Arrays;
 import java.util.ResourceBundle;
+import java.util.concurrent.Executors;
 import javafx.application.Platform;
 import javafx.event.ActionEvent;
 import javafx.fxml.FXML;
@@ -37,6 +38,8 @@ public class EditorController implements Initializable {
     @FXML
     private TitledPane logPane;
 
+    private SyntaxHighlighter syntaxHighlighter;
+
     @FXML
     private void handleMenuExit(ActionEvent event) {
         // TODO: confirmation
@@ -81,9 +84,15 @@ public class EditorController implements Initializable {
     @Override
     public void initialize(URL location, ResourceBundle resources) {
         editor.setParagraphGraphicFactory(LineNumberFactory.get(editor));
+        syntaxHighlighter = new SyntaxHighlighter(editor, Executors.newSingleThreadExecutor());
+        syntaxHighlighter.init();
         editor.replaceText(0, 0, readProgram("/main.hfx"));
     }
 
+    public void stop() {
+        syntaxHighlighter.release();
+    }
+
     private static String readProgram(String path) {
         val fallbackProgram = "composition(640, 480, 25)";
         try (InputStream is = Main.class.getResourceAsStream(path)) {