fi/nimbus/bukkit/plugin/spawnprotector/ProtectPlayer.java

package fi.nimbus.bukkit.plugin.spawnprotector;

/**
 *  Protect player against falling in to the ground during (re)spawning
 */
public class ProtectPlayer implements org.bukkit.event.Listener {
    private static final int PROTECT_COUNT_LIMIT = 100;
    private final org.bukkit.entity.Player player;
    private final org.bukkit.Location spawnLocation;
    private int protectCount;

    /**
     *  Create protector for the player
     */
    public ProtectPlayer(org.bukkit.entity.Player player) {
        this.player = player;
        spawnLocation = player.getLocation();
        protectCount = 0;
    }

    /**
     *  Inspect player movement and decide if him/her requires protection
     */
    @org.bukkit.event.EventHandler(priority = org.bukkit.event.EventPriority.HIGHEST)
    public void playerMoveEvent(org.bukkit.event.player.PlayerMoveEvent event) {
        final org.bukkit.Location location = player.getLocation();

        // Stop protecting if we have moved vertically over 1 square since spawn
        if (distanceSquared2D(location) >= 1.0) {
            stopProtecting(event);
        }

        // Stop protecting if we have moved upwards since spawn
        else if (location.getY() > spawnLocation.getY()) {
            stopProtecting(event);
        }

        // Stop protecting if we have already protected over PROTECT_COUNT_LIMIT times...
        else if (protectCount > PROTECT_COUNT_LIMIT) {
            stopProtecting(event);
            player.sendMessage(org.bukkit.ChatColor.BLUE + "SpawnProtector died of old age");
        }

        // Protect us if we are in free fall!
        else if (location.getY() < spawnLocation.getY()) {
            protect(event);
        }
    }

    /**
     *  Protect player by teleporting him/her back to the spawn level
     */
    private void protect(final org.bukkit.event.player.PlayerMoveEvent event) {
        final org.bukkit.Location location = event.getTo();
        location.setY(spawnLocation.getY());
        player.teleport(location);

        if (protectCount == 0) {
            player.sendMessage(org.bukkit.ChatColor.BLUE + "SpawnProtector active");
        }

        ++protectCount;
    }

    /**
     *  Stop protecting player by unregistering the protection event
     */
    private void stopProtecting(final org.bukkit.event.player.PlayerMoveEvent event) {
        event.getHandlers().unregister(this);
    }

    /**
     *  @return 2D distance moved (squared) since spawning
     */
    private double distanceSquared2D(final org.bukkit.Location location) {
        return Math.abs(spawnLocation.getX() - location.getX()) + Math.abs(spawnLocation.getZ() - location.getZ());
    }
}