Improve logger and dump local logs when a crash happens

src/main/java/com/tibagni/logviewer/LogViewerApplication.java

@@ -20,7 +20,9 @@
 import java.io.*;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.text.SimpleDateFormat;
 import java.util.Arrays;
+import java.util.Date;
 import java.util.Set;
 import java.util.stream.Collectors;
 
@@ -55,8 +57,13 @@ private static void configureUncaughtExceptionHandler() {
     Thread.setDefaultUncaughtExceptionHandler((t, e) -> {
       String fileName = "CRASH-logviewer_" + CommonUtils.calculateStackTraceHash(e) + ".txt";
       Path filePath = Paths.get(System.getProperty("user.home"), fileName);
+      SimpleDateFormat formatter = new SimpleDateFormat("dd-MM HH:mm:ss.SSS");
       try (PrintWriter pw = new PrintWriter(new FileWriter(filePath.toFile()))) {
+        pw.println("Exception happened on thread " + t.getId() + " (" + t.getName() + ") at "
+            + formatter.format(new Date()));
         e.printStackTrace(pw);
+        pw.println("\n---------------- Previous logs before the exception:");
+        Logger.dump(pw);
       } catch (IOException ex) {
         ex.printStackTrace();
       }

src/main/java/com/tibagni/logviewer/logger/Logger.java

@@ -3,10 +3,17 @@
 import com.tibagni.logviewer.rc.LogLevelConfig;
 
 import java.io.PrintStream;
+import java.io.PrintWriter;
+import java.text.DecimalFormat;
 import java.text.SimpleDateFormat;
+import java.util.ArrayDeque;
 import java.util.Date;
 
 public class Logger {
+  private static final int MAX_LOGS_CACHE = 500;
+  private static final ArrayDeque<String> logsCache = new ArrayDeque<>(MAX_LOGS_CACHE);
+  private static final Object logsCacheLock = new Object();
+
   private static LogLevelConfig.Level logLevel = LogLevelConfig.DEFAULT_LEVEL;
 
   private Logger() {}
@@ -74,20 +81,60 @@ public static void error(String message, Throwable throwable) {
     }
   }
 
+  // Use same format as Android so we can use LogViewer to analyze its own logs
   private static void log(LogLevelConfig.Level level, String message) {
-    // 04-02 13:16:34.662  message
-    String pattern = "dd-MM HH:mm:ss.S";
+    // 04-02 13:16:34.662 <pid> <tid> <level> <message>
+    String pattern = "dd-MM HH:mm:ss.SSS";
     SimpleDateFormat simpleDateFormat = new SimpleDateFormat(pattern);
     String date = simpleDateFormat.format(new Date());
 
-    String levelIndicator = level.name().substring(0,1).toUpperCase();
+    String levelIndicator = level.name().substring(0, 1).toUpperCase();
+    DecimalFormat tidFormat = new DecimalFormat("000");
+    String tid = tidFormat.format(Thread.currentThread().getId());
+    String pid = "001"; // TODO use the real PID one day if needed
 
-    String logMessage = date + " " + levelIndicator + " " + message;
+    String logMessage = date + " " + pid + " " + tid + " " + levelIndicator + " " + getCallingClassName() + ": " + message;
     if (level == LogLevelConfig.Level.WARNING || level == LogLevelConfig.Level.ERROR) {
       errorStream.println(logMessage);
     } else {
       debugStream.println(logMessage);
     }
+    addLogToCache(logMessage);
+  }
+
+  private static String getCallingClassName() {
+    StackTraceElement[] stackTraceElements = Thread.currentThread().getStackTrace();
+    if (stackTraceElements.length > 4) {
+      // Index 0 is getStackTrace(), 1 is getCallingClassName(), 2 is log(), 3 is the caller (which is inside
+      // the Logger class), 4 is the actual caller
+      StackTraceElement caller = stackTraceElements[4];
+      String className = caller.getClassName();
+      int lastDotIndex = className.lastIndexOf('.');
+      if (lastDotIndex != -1 && lastDotIndex < className.length() - 1) {
+        return className.substring(lastDotIndex + 1);
+      }
+      return className; // If there is no package name
+    }
+    return "Unknown";
+  }
+
+  private static void addLogToCache(String log) {
+    synchronized (logsCacheLock) {
+      if (logsCache.size() >= MAX_LOGS_CACHE) {
+        // We reached the maximum size, drop the first log before inserting the new one
+        logsCache.pollFirst();
+      }
+
+      logsCache.add(log);
+    }
+  }
+
+  public static void dump(PrintWriter pw) {
+    synchronized (logsCacheLock) {
+      while (!logsCache.isEmpty()) {
+        pw.println(logsCache.removeFirst());
+      }
+    }
   }
 
   static boolean isLoggable(LogLevelConfig.Level level) {

src/main/java/com/tibagni/logviewer/rc/LogLevelConfig.java

@@ -10,7 +10,7 @@ public enum Level {
         WARNING,
         ERROR
     }
-    public static final Level DEFAULT_LEVEL = Level.DEBUG;
+    public static final Level DEFAULT_LEVEL = Level.WARNING;
     private final Level levelConfig;
 
     public LogLevelConfig(String value) {