Decimation_Mod/Content/Projectiles/NPC/Bone.cs

using Decimation.Lib.Items;
using Decimation.Lib.Util;
using Microsoft.Xna.Framework;
using Terraria;
using Terraria.ID;

namespace Decimation.Content.Projectiles.NPC
{
    internal class Bone : DecimationProjectile
    {
        private const int IdlingCounterMax = 60;
        private const int TargetingCounterMax = 90;
        private const float IdlingVelocity = 5f;
        private const float AttackingVelocity = 10f;

        private AiState State
        {
            get
            {
                {
                    switch ((int) projectile.ai[0])
                    {
                        case 0: return AiState.Idling;
                        case 1: return AiState.Targeting;
                        default: return AiState.Attacking;
                    }
                }
            }
            set
            {
                int state;
                switch (value)
                {
                    case AiState.Idling:
                        state = 0;
                        break;
                    case AiState.Targeting:
                        state = 1;
                        break;
                    default:
                        state = 2;
                        break;
                }

                projectile.ai[0] = state;
            }
        }

        private int Counter
        {
            get => (int) projectile.ai[1];
            set => projectile.ai[1] = value;
        }

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

        private Player TargetPlayer => Main.player[Target];

        protected override void Init()
        {
            projectile.width = 14;
            projectile.height = 34;
            projectile.aiStyle = -1;
            projectile.ignoreWater = true;
            projectile.tileCollide = false;
            DamageType = DecimationWeapon.DamageType.Ranged;
            projectile.hostile = true;
            projectile.friendly = false;
            projectile.penetrate = -1;
            projectile.hostile = false;
            projectile.friendly = false;
            projectile.timeLeft = 600;
            Damages = Main.expertMode ? 57 : 20;
            Target = 255;
        }

        public override void AI()
        {
            if (State == AiState.Idling)
            {
                projectile.rotation += MathHelper.Pi * (1 / 64f);
                projectile.velocity.Normalize();
                projectile.velocity *= IdlingVelocity;

                if (Counter > IdlingCounterMax)
                {
                    Counter = 0;
                    State = AiState.Targeting;
                }

                Counter++;
            }
            else if (State == AiState.Targeting)
            {
                projectile.velocity *= 0f;
                projectile.rotation += MathHelper.Pi * (1 / 64f) * (1 + Counter / 10);

                if (Counter > TargetingCounterMax)
                {
                    FindTarget();
                    
                    if (TargetPlayer == null || !TargetPlayer.active || TargetPlayer.dead)
                    {
                        projectile.Kill();
                        return;
                    }

                    Vector2 velocity = TargetPlayer.Center - projectile.Center;
                    velocity.Normalize();
                    velocity *= AttackingVelocity;
                    
                    projectile.hostile = true;
                    projectile.velocity = velocity;
                    projectile.penetrate = 1;

                    State = AiState.Attacking;
                }

                Counter++;
            }
            else if (State == AiState.Attacking)
            {
                if (TargetPlayer == null || !TargetPlayer.active || TargetPlayer.dead)
                {
                    projectile.Kill();
                    return;
                }

                projectile.rotation += MathHelper.Pi * (1 / 64f) * (1 + Counter / 10);
            }

            int dust = Dust.NewDust(projectile.position, projectile.width, projectile.height, DustID.Blood);
            Main.dust[dust].noGravity = true;
            Lighting.AddLight(projectile.Center, LightingUtils.Rgb255ToRgb1(158, 6, 6));
        }

        public override void Kill(int timeLeft)
        {
            DustUtils.NewDustCircle(8, projectile.position, projectile.width, projectile.height, DustID.Blood,
                projectile.scale * 2f);
        }

        public override void OnHitPlayer(Player target, int damage, bool crit)
        {
            if (Main.expertMode && Main.rand.Next(100) < 35) target.AddBuff(BuffID.Confused, 600);
        }

        private void FindTarget()
        {
            if (Target >= 255)
            {
                float lastDistance = float.MaxValue;

                for (int i = 0; i < Main.player.Length; i++)
                {
                    Player player = Main.player[i];
                    if (player != null && player.active && !player.dead)
                    {
                        float distance = projectile.Distance(player.Center);
                        if (distance < lastDistance)
                        {
                            lastDistance = distance;
                            Target = i;
                        }
                    }
                }
            }
        }

        private enum AiState
        {
            Idling = 0,
            Targeting = 1,
            Attacking = 2
        }
    }
}