1  package hlt;
 2  
 3  import java.io.FileWriter;
 4  import java.io.IOException;
 5  import java.util.ArrayList;
 6  
 7  public class Log {
 8      private final FileWriter file;
 9  
10      private static Log INSTANCE;
11      private static ArrayList<String> LOG_BUFFER = new ArrayList<>();
12  
13      static {
14          Runtime.getRuntime().addShutdownHook(new AtExit());
15      }
16  
17      private static class AtExit extends Thread {
18          @Override
19          public void run() {
20              if (INSTANCE != null) {
21                  return;
22              }
23  
24              final long now_in_nanos = System.nanoTime();
25              final String filename = "bot-unknown-" + now_in_nanos + ".log";
26              try (final FileWriter writer = new FileWriter(filename)) {
27                  for (final String message : LOG_BUFFER) {
28                      writer.append(message).append('\n');
29                  }
30              } catch (final IOException e) {
31                  // Nothing much we can do here.
32              }
33          }
34      }
35  
36      private Log(final FileWriter f) {
37          file = f;
38      }
39  
40      static void open(final int botId) {
41          if (INSTANCE != null) {
42              Log.log("Error: log: tried to open(" + botId + ") but we have already opened before.");
43              throw new IllegalStateException();
44          }
45  
46          final String filename = "bot-" + botId + ".log";
47          final FileWriter writer;
48          try {
49              writer = new FileWriter(filename);
50          } catch (final IOException e) {
51              throw new IllegalStateException(e);
52          }
53          INSTANCE = new Log(writer);
54  
55          try {
56              for (final String message : LOG_BUFFER) {
57                  writer.append(message).append('\n');
58              }
59          } catch (final IOException e) {
60              throw new IllegalStateException(e);
61          }
62          LOG_BUFFER.clear();
63      }
64  
65      public static void log(final String message) {
66          if (INSTANCE == null) {
67              LOG_BUFFER.add(message);
68              return;
69          }
70  
71          try {
72              INSTANCE.file.append(message).append('\n').flush();
73          } catch (final IOException e) {
74              e.printStackTrace();
75          }
76      }
77  }