package net.runelite.client.plugins.hydra;

import com.google.inject.Provides;
import lombok.AccessLevel;
import lombok.Getter;
import net.runelite.api.*;
import net.runelite.api.coords.LocalPoint;
import net.runelite.api.coords.WorldPoint;
import net.runelite.api.events.*;
import net.runelite.client.config.ConfigManager;
import net.runelite.client.eventbus.Subscribe;
import java.util.*;
import net.runelite.client.plugins.Plugin;
import net.runelite.client.plugins.PluginDescriptor;
import net.runelite.client.ui.overlay.OverlayManager;
import javax.inject.Inject;
import java.util.List;

@PluginDescriptor(
        name = " Hydra",
        description = "Helps you kill hydra",
        tags = {"hydra", "slayer", "pvm"},
        enabledByDefault =false
)
public class HydraPlugin extends Plugin {

    @Inject
    private Client client;

    @Getter(AccessLevel.PUBLIC)
    @Inject
    private OverlayManager overlayManager;

    @Inject
    private HydraConfig config;

    @Inject
    private HydraOverlay overlay;

    public boolean isMage = false;
    public int HydraCounter = 0;
    private boolean lastphase = false;
    private int NumberAttacks = 0;
    public Set<Integer> HydraID = new HashSet<>();

    NPC hydra = null;

    @Provides
    HydraConfig provideConfig(ConfigManager configManager)
    {
        return configManager.getConfig(HydraConfig.class);
    }

    @Override
    protected void startUp() throws Exception
    {
        HydraID.add(8615);HydraID.add(8619);HydraID.add(8620);HydraID.add(8621);
        overlayManager.add(overlay);
    }

    @Override
    protected void shutDown() throws Exception
    {
        overlayManager.remove(overlay);
    }

    @Subscribe
    public void onGameTick(GameTick tick) {

        List<NPC> npcs = client.getNpcs();
        if (npcs == null) { return; }
        //if (!client.isInInstancedRegion()) { return; }
        for (NPC npc : npcs) {
            if (HydraID.contains(npc.getId())) {
                this.hydra = npc;
                if (this.hydra.getHealth() <= 275) {
                    lastphase = true;
                }
            }
        }

        List<Projectile> p = client.getProjectiles();
        for ( Projectile P: p ) {
            int id = P.getId();
            HandleCounter(id);
        }

        this.HydraCounter--;
        if (HydraCounter < 0) {
            HydraCounter = 0;
        }
    }

    private void HandleCounter(int projid) {

        if (projid == ProjectileID.HYDRA_MAGE || projid == ProjectileID.HYDRA_RANGE) {
            if (NumberAttacks==0) {
                if (projid == ProjectileID.HYDRA_MAGE) {
                    this.NumberAttacks++;
                    this.isMage = true;
                    HydraCounter = 7;
                }
            }
            if (HydraCounter < 2) {
                this.NumberAttacks++;
                if (lastphase) {
                    this.isMage = !this.isMage;
                }
                else if (this.NumberAttacks-1 % 3 == 0) {
                    this.isMage = !this.isMage;
                }
                HydraCounter = 7;
            }

        }

        else {
            if (HydraCounter < 2) {
                HydraCounter = 7;
            }
        }
    }

    @Subscribe
    public void onNpcDespawned(NpcDespawned despawned){
            NumberAttacks = 0;
    }
}

******** HydraOverlay.java ********


package net.runelite.client.plugins.hydra;

import net.runelite.api.*;
import net.runelite.api.Point;
import net.runelite.api.coords.LocalPoint;
import net.runelite.client.ui.overlay.*;
import javax.inject.Inject;
import java.awt.*;

public class HydraOverlay extends Overlay {

    private Client client;
    private final HydraPlugin plugin;

    @Inject
    public HydraOverlay(Client client, HydraPlugin plugin)
    {
        this.client = client;
        this.plugin = plugin;
        setPosition(OverlayPosition.DYNAMIC);
        setLayer(OverlayLayer.ABOVE_SCENE);
    }

    @Override
    public Dimension render(Graphics2D graphics)
    {
        graphics.setFont(new Font("Arial", Font.BOLD, 20));
        NPC npc = plugin.hydra;

        if((npc == null) || !client.isInInstancedRegion()){
            return null;
        }

        if (plugin.HydraCounter >= 0) {

                String str = Integer.toString(plugin.HydraCounter);
                LocalPoint lp = npc.getLocalLocation();

                //Point textLocation = Perspective.getCanvasTextLocation(client, graphics, lp, str, 0);

                Point textLocation = npc.getCanvasTextLocation(graphics, npc.getName(), 0);

                if (plugin.isMage) {
                    OverlayUtil.renderTextLocation(graphics, textLocation, str, Color.BLUE);
                } else {
                    OverlayUtil.renderTextLocation(graphics, textLocation, str, Color.GREEN);
                }
        }
        return null;
}