add command line parser, implement logging

.gitignore

@@ -14,4 +14,6 @@ buildNumber.properties
 # Eclipse Core
 .project
 # JDT-specific (Eclipse Java Development Tools)
-.classpath
+.classpath
+# Log files
+log/

notes.txt

@@ -12,3 +12,8 @@ on successful peer list retrieval - local tracker cache updated. If not, peers f
 On re-announce to destination trackers, proxied peer's real IP must be injected into announce request and
 other parameters should remain same as in original request.
 
+
+
+
+Maven exec with args:
+	mvn exec:java -Dexec.args=''

pom.xml

@@ -45,6 +45,21 @@
     	<artifactId>netty-buffer</artifactId>
     	<version>4.1.114.Final</version>
     </dependency>
+    <dependency>
+    	<groupId>commons-cli</groupId>
+    	<artifactId>commons-cli</artifactId>
+    	<version>1.9.0</version>
+    </dependency>
+    <dependency>
+    	<groupId>org.slf4j</groupId>
+    	<artifactId>slf4j-api</artifactId>
+    	<version>2.0.16</version>
+    </dependency>
+    <dependency>
+    	<groupId>ch.qos.logback</groupId>
+    	<artifactId>logback-classic</artifactId>
+    	<version>1.5.11</version>
+    </dependency>
   </dependencies>
 
   <build>

src/main/java/com/mykola2312/retracker/App.java

@@ -1,10 +1,69 @@
 package com.mykola2312.retracker;
 
-/**
- * Hello world!
- */
+import java.io.File;
+import java.nio.file.Path;
+
+import org.apache.commons.cli.CommandLine;
+import org.apache.commons.cli.DefaultParser;
+import org.apache.commons.cli.Option;
+import org.apache.commons.cli.Options;
+import org.apache.commons.cli.ParseException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.LoggerContext;
+import ch.qos.logback.classic.encoder.PatternLayoutEncoder;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.FileAppender;
+
 public class App {
+	private static final Logger log = LoggerFactory.getLogger(App.class);
+	
 	public static void main(String[] args) {
-    	System.out.println("Hello World!");
+		final Options options = new Options()
+				.addOption("l", "log", true, "log dir path");
+		final Option logDirOpt = options.getOption("log");
+		
+		CommandLine cli = null;
+		try {
+			cli = new DefaultParser().parse(options, args);
+		} catch (ParseException e) {
+			System.err.printf("Argument error: %s\n", e.toString());
+			System.exit(1);
+		}
+		
+		String logDirPath = cli.getOptionValue(logDirOpt);
+		if (logDirPath != null) {
+			// setup file logging
+			File logDir = new File(logDirPath);
+			if (!logDir.exists()) {
+				if (!logDir.mkdir()) {
+					System.err.println("Failed to create log dir");
+					System.exit(1);
+				}
+			}
+			
+			// https://stackoverflow.com/questions/47299109/programmatically-add-appender-in-logback	
+			final LoggerContext lc = (LoggerContext)LoggerFactory.getILoggerFactory();
+			final PatternLayoutEncoder ple = new PatternLayoutEncoder();
+			ple.setPattern("%d{HH:mm:ss} %-5level %logger{0} - %msg%n");
+			ple.setContext(lc);
+			ple.start();
+			
+			FileAppender<ILoggingEvent> fileAppender = new FileAppender<ILoggingEvent>();
+			fileAppender.setFile(Path.of(logDirPath, "log_out.log").toString());
+			fileAppender.setEncoder(ple);
+			fileAppender.setContext(lc);
+			fileAppender.start();
+			
+			ch.qos.logback.classic.Logger logbackLogger =
+	                (ch.qos.logback.classic.Logger)LoggerFactory.getLogger("com.mykola2312");
+			logbackLogger.addAppender(fileAppender);
+			logbackLogger.setLevel(Level.INFO);
+			logbackLogger.setAdditive(false);
+		}
+		
+		log.info("retracker started!");
 	}
 }

src/main/resources/logback.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+	<appender name="CONSOLE"  class="ch.qos.logback.core.ConsoleAppender">
+		<layout class="ch.qos.logback.classic.PatternLayout">
+			<Pattern>
+				%d{HH:mm:ss} %highlight(%-5level) %logger{0} - %msg%n
+			</Pattern>
+		</layout>
+	</appender>
+	
+	<logger name="com.mykola2312" level="info" additivity="false">
+		<appender-ref ref="CONSOLE"/>
+	</logger>
+	
+	<root level="info">
+		<appender-ref ref="CONSOLE"/>
+	</root>
+</configuration>