Implement helper functions for accessing offline players

src/dev/w1zzrd/spigot/wizcompat/OfflinePlayers.java

@@ -0,0 +1,108 @@
+package dev.w1zzrd.spigot.wizcompat;
+
+import org.bukkit.Bukkit;
+import org.bukkit.Server;
+import org.bukkit.World;
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.Player;
+
+import java.io.File;
+import java.util.Arrays;
+import java.util.Objects;
+import java.util.Set;
+import java.util.UUID;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public final class OfflinePlayers {
+    private OfflinePlayers(){ throw new UnsupportedOperationException("Functional class"); }
+
+    private static int totalFiles = -1;
+    private static Set<UUID> fileUUIDs = null;
+
+    private static Set<UUID> getFileUUIDsAggressive(final Server server) {
+        return server.getWorlds().stream().flatMap(world -> {
+            File[] playerDataFiles = new File(world.getWorldFolder(), "playerdata").listFiles();
+
+            if (playerDataFiles == null)
+                return Stream.empty();
+
+            return Arrays.stream(playerDataFiles)
+                    .filter(file -> file.getName().endsWith(".dat"))
+                    .map(file -> {
+                        try {
+                            return UUID.fromString(file.getName().substring(0, file.getName().indexOf('.')));
+                        } catch (IllegalArgumentException badName) {
+                            return null;
+                        }
+                    })
+                    .filter(Objects::nonNull);
+        }).collect(Collectors.toSet());
+    }
+
+    private static Set<UUID> getFileUUIDsLazy(final Server server) {
+        int totalFiles = 0;
+        for (final World world : server.getWorlds()) {
+            final File worldFolder = new File(world.getWorldFolder(), "playerdata");
+            final String[] fileNames = worldFolder.list();
+
+            if (fileNames != null)
+                totalFiles += fileNames.length;
+        }
+
+        // Assume no data files have been deleted
+        // I.e. if there is not change in the dat file count, we assume no new players have been seen
+        if (OfflinePlayers.totalFiles != totalFiles || fileUUIDs == null) {
+            final Set<UUID> found = getFileUUIDsAggressive(server);
+            OfflinePlayers.totalFiles = totalFiles;
+
+            fileUUIDs = found;
+            return found;
+        }
+
+        return fileUUIDs;
+    }
+
+    /**
+     * Get UUIDs of all players known to this server
+     * @param server Server to get player UUIDs for
+     * @return Array of all UUIDs of players on the server
+     */
+    public static UUID[] getAllKnownPlayers(final Server server, final boolean lazyFileLoading) {
+        final Set<UUID> fileUUIDS = lazyFileLoading ? getFileUUIDsLazy(server) : getFileUUIDsAggressive(server);
+
+        // Add online players, in case (for some reason idk) the online player data hasn't yet been saved to a file
+        // This is probably unnecessary
+        fileUUIDS.addAll(server.getOnlinePlayers().stream().map(Entity::getUniqueId).collect(Collectors.toSet()));
+
+        return fileUUIDS.toArray(new UUID[0]);
+    }
+
+    /**
+     * Find a player on the server by name
+     * @param server Server to find player for
+     * @param playerName Name of player to find
+     * @param ignoreCase Whether or not to respect case-sensitivity
+     * @return Matching player instance, or null if server does not know of a player with the given name
+     */
+    public static Player getKnownPlayer(final Server server, final String playerName, final boolean ignoreCase, final boolean lazyFileLoading) {
+        for (final UUID uuid : getAllKnownPlayers(server, lazyFileLoading)) {
+            final Player player = Bukkit.getPlayer(uuid);
+
+            if (player != null && ((ignoreCase && player.getName().equalsIgnoreCase(playerName)) || (!ignoreCase && player.getName().equals(playerName))))
+                return player;
+        }
+
+        return null;
+    }
+
+    /**
+     * Find a player on the server by name
+     * @param server Server to find player for
+     * @param playerName Name of player to find
+     * @return Matching player instance, or null if server does not know of a player with the given name
+     */
+    public static Player getKnownPlayer(final Server server, final String playerName) {
+        return getKnownPlayer(server, playerName, true, true);
+    }
+}