Add Java example of fatal error handler.

example/java/org/drinkless/tdlib/example/Example.java

@@ -17,6 +17,7 @@ import java.util.NavigableSet;
 import java.util.TreeSet;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
@@ -606,9 +607,80 @@ public final class Example {
         @Override
         public void onLogMessage(int verbosityLevel, String message) {
             if (verbosityLevel == 0) {
-                // a fatal error, the app will crash right after the function returns
+                onFatalError(message);
+                return;
             }
             System.err.println(message);
         }
     }
+
+    private static void onFatalError(String errorMessage) {
+        final class ThrowError implements Runnable {
+            private final String errorMessage;
+            private final AtomicLong errorThrowTime;
+
+            private ThrowError(String errorMessage, AtomicLong errorThrowTime) {
+                this.errorMessage = errorMessage;
+                this.errorThrowTime = errorThrowTime;
+            }
+
+            @Override
+            public void run() {
+                if (isDatabaseBrokenError(errorMessage) || isDiskFullError(errorMessage) || isDiskError(errorMessage)) {
+                    processExternalError();
+                    return;
+                }
+
+                errorThrowTime.set(System.currentTimeMillis());
+                throw new ClientError("TDLib fatal error: " + errorMessage);
+            }
+
+            private void processExternalError() {
+                errorThrowTime.set(System.currentTimeMillis());
+                throw new ExternalClientError("Fatal error: " + errorMessage);
+            }
+
+            private static final class ClientError extends Error {
+                private ClientError(String message) {
+                    super(message);
+                }
+            }
+
+            private static final class ExternalClientError extends Error {
+                public ExternalClientError(String message) {
+                    super(message);
+                }
+            }
+
+            private static boolean isDatabaseBrokenError(String message) {
+                return message.contains("Wrong key or database is corrupted") ||
+                        message.contains("SQL logic error or missing database") ||
+                        message.contains("database disk image is malformed") ||
+                        message.contains("file is encrypted or is not a database") ||
+                        message.contains("unsupported file format") ||
+                        message.contains("Database was corrupted and deleted during execution and can't be recreated");
+            }
+
+            private static boolean isDiskFullError(String message) {
+                return message.contains("PosixError : No space left on device") ||
+                        message.contains("database or disk is full");
+            }
+
+            private static boolean isDiskError(String message) {
+                return message.contains("I/O error") || message.contains("Structure needs cleaning");
+            }
+        }
+
+        final AtomicLong errorThrowTime = new AtomicLong(Long.MAX_VALUE);
+        new Thread(new ThrowError(errorMessage, errorThrowTime), "TDLib fatal error thread").start();
+
+        // wait at least 10 seconds after the error is thrown
+        while (errorThrowTime.get() >= System.currentTimeMillis() - 10000) {
+            try {
+                Thread.sleep(1000 /* milliseconds */);
+            } catch (InterruptedException ignore) {
+                Thread.currentThread().interrupt();
+            }
+        }
+    }
 }