Added automatic cleanup of backups folder

By default mcMMO keeps the following files:
 * All files from the last 24 hours
 * Daily backups of the past week
 * Weekly backups of the past months

Adds #1574

src/main/java/com/gmail/nossr50/runnables/backups/CleanBackupsTask.java

@@ -0,0 +1,115 @@
+package com.gmail.nossr50.runnables.backups;
+
+import java.io.File;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.util.ArrayList;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+import org.bukkit.scheduler.BukkitRunnable;
+
+import com.gmail.nossr50.config.Config;
+import com.gmail.nossr50.mcMMO;
+
+public class CleanBackupsTask extends BukkitRunnable {
+    private static final String BACKUP_DIRECTORY = mcMMO.getMainDirectory() + "backup" + File.separator;
+    private static final File BACKUP_DIR = new File(BACKUP_DIRECTORY);
+
+    @Override
+    public void run() {
+        List<Integer> savedDays = new ArrayList<Integer>();
+        List<Integer> savedWeeks = new ArrayList<Integer>();
+        List<File> toDelete = new ArrayList<File>();
+        int amountTotal = 0;
+        int amountDeleted = 0;
+
+        // Check files in backup folder from oldest to newest
+        for (File file : BACKUP_DIR.listFiles()) {
+            if (!file.isFile()) {
+                continue;
+            }
+
+            amountTotal++;
+            String fileName = file.getName();
+            fileName = fileName.split("[.]")[0];
+
+            Date date = getDate(fileName);
+
+            if (date == null) {
+                mcMMO.p.debug("Could not determine date for file: " + fileName);
+                continue;
+            }
+
+            Calendar cal = Calendar.getInstance();
+            cal.setTime(date);
+            int dayOfWeek = cal.get(Calendar.DAY_OF_WEEK);
+            int weekOfYear = cal.get(Calendar.WEEK_OF_YEAR);
+
+            if (isPast24Hours(date) && Config.getInstance().getKeepLast24Hours()) {
+                // Keep all files from the last 24 hours
+                continue;
+            }
+            else if (isLastWeek(date) && !savedDays.contains(dayOfWeek)  && Config.getInstance().getKeepDailyLastWeek()) {
+                // Keep daily backups of the past week
+                savedDays.add(dayOfWeek);
+                continue;
+            }
+            else if (!savedWeeks.contains(weekOfYear) && Config.getInstance().getKeepWeeklyPastMonth()) {
+                // Keep one backup of each week
+                savedWeeks.add(weekOfYear);
+                continue;
+            }
+
+            amountDeleted++;
+            toDelete.add(file);
+        }
+
+        mcMMO.p.getLogger().info("Cleaning backup files... (" + amountDeleted + "/" + amountTotal + ")");
+
+        for (File file : toDelete) {
+            mcMMO.p.debug("Deleted: " + file.getName());
+            file.delete();
+        }
+    }
+
+    /**
+     * Check if date is within last 24 hours
+     *
+     * @param date date to check
+     *
+     * @return true is date is within last 24 hours, false if otherwise
+     */
+    private boolean isPast24Hours(Date date) {
+        Date modifiedDate = new Date(System.currentTimeMillis() - TimeUnit.MILLISECONDS.convert(24, TimeUnit.HOURS));
+        return date.after(modifiedDate);
+    }
+
+    /**
+     * Check if date is within the last week
+     *
+     * @param date date to check
+     *
+     * @return true is date is within the last week, false if otherwise
+     */
+    private boolean isLastWeek(Date date) {
+        Date modifiedDate = new Date(System.currentTimeMillis() - TimeUnit.MILLISECONDS.convert(7, TimeUnit.DAYS));
+        return date.after(modifiedDate);
+    }
+
+    private Date getDate(String fileName) {
+        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH-mm-ss");
+        Date date;
+
+        try {
+            date = dateFormat.parse(fileName);
+        }
+        catch (ParseException e) {
+            return null;
+        }
+
+        return date;
+    }
+}