Logger.java

package com.team254.lib.util;

import edu.wpi.first.wpilibj.Timer;

import java.io.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.stream.Collectors;

public class Logger {

    public static final double WRITE_TIME = 0.5; // Write every .5 seconds

    private static Logger inst = null;

    protected File logFile = null;
    private BufferedWriter writer;
    private ArrayBlockingQueue<String> logMessages = new ArrayBlockingQueue<String>(
            300);
    Thread consumer;

    public static Logger getInstance() {
        if (inst == null) {
            inst = new Logger();
        }
        return inst;
    }

    Runnable consumerTask = new Runnable() {
        public void run() {
            double lastWriteTime = Timer.getFPGATimestamp();
            while (true) {
                try {
                    String msg = logMessages.take();
                    writer.write(msg);
                    if (Timer.getFPGATimestamp() >= lastWriteTime + WRITE_TIME) {
                        writer.flush();
                        lastWriteTime = Timer.getFPGATimestamp();
                    }
                } catch (InterruptedException | IOException e) {
                    e.printStackTrace();
                }
            }
        }
    };

    private Logger() {
        File baseDrive = determineMountPoint();
        if (baseDrive != null) {
            File logDir = new File(baseDrive, "logs");
            if (!logDir.exists()) {
                logDir.mkdirs();
            }

            File lastBoot = getLastBootLogFile();
            int number = 0;
            if (lastBoot != null) {
                String name = lastBoot.getName();
                String numberStr = name.substring(0, name.lastIndexOf('.'));
                number = Integer.parseInt(numberStr);
            }
            logFile = new File(logDir, String.format("%04d.log", number + 1));
            try {
                writer = new BufferedWriter(new OutputStreamWriter(
                        new FileOutputStream(logFile), "utf-8"));
            } catch (IOException e) {
                e.printStackTrace();
            }
            consumer = new Thread(consumerTask);
            consumer.setName("Logger");
            consumer.setPriority(Thread.MIN_PRIORITY);
            consumer.start();
        }

    }

    protected static File determineMountPoint() {
        char iter = 'z';
        for (int i = 0; i < 6; i++) {
            File f = new File("/" + iter);
            if (f.exists() && f.isDirectory()) {
                return f;
            }
            iter--;
        }
        return null;
    }

    public static File getLogDirectory() {
        File baseDrive = determineMountPoint();
        if (baseDrive == null) {
            return null;
        }
        return new File(baseDrive, "logs");
    }

    public static File getLastBootLogFile() {
        List<String> fileNames = getAllLogFiles().stream()
                .map(File::getName).collect(Collectors.toList());
        fileNames.sort(null);
        if (fileNames.size() <= 0)
            return null;
        String lastFileName = fileNames.get(fileNames.size() - 1);
        return new File(getLogDirectory(), lastFileName);
    }

    public static Collection<File> getAllLogFiles() {
        FilenameFilter logFilter = new FilenameFilter() {
            public boolean accept(File dir, String name) {
                String lowercaseName = name.toLowerCase();
                return lowercaseName.matches("\\d\\d\\d\\d.log");
            }
        };
        File logDir = getLogDirectory();
        File[] files = logDir.listFiles(logFilter);
        if (files == null) {
            return new ArrayList<File>();
        } else {
            return Arrays.asList(files);
        }
    }

    protected File getCurrentLogFile() {
        return logFile;
    }

    public static File getLogFile() {
        return getInstance().getCurrentLogFile();
    }

    private boolean printLocal(String s) {
        return logMessages.offer(s);
    }

    public static boolean print(String s) {
        return getInstance().printLocal(s);
    }

    private boolean printlnLocal(String s) {
        return logMessages.offer(s + '\n');
    }

    public static boolean println(String s) {
        return getInstance().printlnLocal(s);
    }
}