Fixes UCI engine shutdown process

src/main/java/com/fathzer/jchess/bot/uci/EngineLoader.java

@@ -33,7 +33,8 @@ public static Map<String, Engine> loadEngines(final Path path) throws IOExceptio
 		final List<String> commands = Files.readAllLines(path);
 		for (String command : commands) {
 			if (!command.isBlank() && !command.startsWith("#")) {
-				try (UCIEngine engine = new UCIEngine(command)) {
+				try {
+					UCIEngine engine = new UCIEngine(command);
 					engines.put(engine.getName(), engine);
 					log.info("engine {} is loaded",engine.getName());
 				} catch (IOException e) {

src/main/java/com/fathzer/jchess/bot/uci/StdErrReader.java

@@ -0,0 +1,50 @@
+package com.fathzer.jchess.bot.uci;
+
+import java.io.BufferedReader;
+import java.io.Closeable;
+import java.io.EOFException;
+import java.io.IOException;
+
+class StdErrReader implements Closeable, Runnable {
+	private final BufferedReader errorReader;
+	private final Thread spyThread;
+	private boolean stopped;
+
+	StdErrReader(Process process) {
+		this.errorReader = process.errorReader();
+		this.spyThread = new Thread(this);
+		this.spyThread.setDaemon(true);
+		this.spyThread.start();
+	}
+
+	@Override
+	public void run() {
+		while (!stopped) {
+			try {
+				final String line = errorReader.readLine();
+				if (line!=null) {
+					System.err.println (line); //TODO
+				}
+			} catch (EOFException e) {
+				if (!stopped) {
+					log(e);
+				}
+			} catch (IOException e) {
+				log(e);
+			}
+		}
+	}
+
+	private void log(IOException e) {
+		synchronized(System.err) {
+			System.err.println("An error occured, stopped is "+ stopped);
+			e.printStackTrace(); //TODO
+		}
+	}
+
+	@Override
+	public void close() throws IOException {
+		this.stopped = true;
+		this.errorReader.close();
+	}
+}

src/main/java/com/fathzer/jchess/bot/uci/UCIEngine.java

@@ -7,6 +7,7 @@
 import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.TimeUnit;
 
 import com.fathzer.jchess.bot.Engine;
 import com.fathzer.jchess.bot.Move;
@@ -21,6 +22,7 @@ public class UCIEngine implements Closeable, Engine {
 	private final String name;
 	private final BufferedReader reader;
 	private final BufferedWriter writer;
+	private final StdErrReader errorReader;
 	private final List<Option<?>> options;
 
 	public UCIEngine(String path) throws IOException {
@@ -30,6 +32,7 @@ public UCIEngine(String path) throws IOException {
 		this.process = processBuilder.start();
 		this.reader = process.inputReader();
 		this.writer = process.outputWriter();
+		this.errorReader = new StdErrReader(process);
 		this.options = new ArrayList<>();
 		this.name = init();
 	}
@@ -107,8 +110,14 @@ public Move play(PlayParameters params) {
 
 	@Override
 	public void close() throws IOException {
+		this.write("quit");
 		this.reader.close();
 		this.writer.close();
-		this.process.destroy();
+		this.errorReader.close();
+		try {
+			this.process.waitFor(5, TimeUnit.SECONDS);
+		} catch (InterruptedException e) {
+			this.process.destroy();
+		}
 	}
 }