Decimation_Mod/Content/Projectiles/Boss/DuneWyrm/Timekeeper.cs

using System;
using Decimation.Lib.Items;
using Microsoft.Xna.Framework;
using Terraria;

namespace Decimation.Content.Projectiles.Boss.DuneWyrm
{
    public class Timekeeper : DecimationProjectile
    {
        protected override int Damages => 45;
        protected override DecimationWeapon.DamageType DamageType => DecimationWeapon.DamageType.Ranged;

        private int Sibling
        {
            get => (int) projectile.localAI[0];
            set => projectile.localAI[0] = value;
        }

        private float Rotation
        {
            get => projectile.localAI[1];
            set => projectile.localAI[1] = value;
        }

        private Projectile SiblingProjectile => Main.projectile[Sibling];

        private int Counter
        {
            get => (int) projectile.ai[0];
            set => projectile.ai[0] = value;
        }

        private bool IsChild => projectile.ai[1] == 1f;

        private float Speed { get; set; }
        private bool Initialization { get; set; } = true;

        protected override void Init()
        {
            projectile.width = 12;
            projectile.height = 12;
            projectile.penetrate = -1;
            projectile.aiStyle = -1;
            projectile.timeLeft = 600;

            Sibling = -1;
        }

        public override bool PreKill(int timeLeft)
        {
            SiblingProjectile?.Kill();

            return true;
        }

        public override void Kill(int timeLeft)
        {
            for (int i = 0; i < 8; i++)
            {
                Dust.NewDust(projectile.position, projectile.width, projectile.height, 135, 0,
                    0, 100, default, 4f * projectile.scale);
            }
        }

        public override void AI()
        {
            if (!IsChild)
            {
                if (Sibling == -1)
                {
                    projectile.position.Y -= 8f;

                    Rotation = projectile.velocity.ToRotation();
                    Speed = projectile.velocity.Length();

                    Sibling = Projectile.NewProjectile(projectile.position, new Vector2(Speed, Rotation),
                        projectile.type,
                        projectile.damage, projectile.knockBack, projectile.owner, 0, 1);
                }

                // Parent
                Vector2 parentVelocity = new Vector2(0, 1) * (float) (1.5f * Math.Sin(Counter * (1 / 8f)));
                parentVelocity.X = Speed;
                projectile.velocity = parentVelocity.RotatedBy(Rotation);

                // Sibling
                Vector2 siblingVelocity = parentVelocity * new Vector2(1, -1);
                SiblingProjectile.velocity = siblingVelocity.RotatedBy(Rotation);

                if (Initialization)
                {
                    Vector2 offset = new Vector2(projectile.position.X - SiblingProjectile.position.X, -16);
                    projectile.velocity += offset.RotatedBy(Rotation);

                    Initialization = false;
                }

                Counter++;
            }
            else if (IsChild && Sibling == -1)
            {
                Sibling = projectile.owner;
            }

            Lighting.AddLight(projectile.Center, 0f, 0f, 1f);
            Dust.NewDust(projectile.position, projectile.width, projectile.height, 135, projectile.velocity.X * 0.2f,
                projectile.velocity.Y * 0.2f, 100, default, 2f * projectile.scale);
        }
    }
}