minecraft-kajetans-mod/src/main/java/me/km/entities/EntityItemProjectile.java

package me.km.entities;

import java.util.List;
import me.km.KajetansMod;
import me.km.snuviscript.ScriptEvents;
import me.km.utils.ReflectionUtils;
import net.minecraft.entity.Entity;
import net.minecraft.entity.LivingEntity;
import net.minecraft.entity.IProjectile;
import net.minecraft.entity.item.ItemEntity;
import net.minecraft.entity.player.PlayerEntity;
import net.minecraft.item.ItemStack;
import net.minecraft.util.DamageSource;
import net.minecraft.util.math.AxisAlignedBB;
import net.minecraft.util.math.MathHelper;
import net.minecraft.util.math.Vec3d;

public class EntityItemProjectile extends ItemEntity implements IProjectile
{
    private final LivingEntity thrower;
    private boolean noHit;
    private final float damage;

    public EntityItemProjectile(LivingEntity thrower, ItemStack stack, float damage) 
    {
        super(thrower.world, thrower.posX, thrower.posY + thrower.getEyeHeight() - 0.1d, thrower.posZ, stack);
        this.thrower = thrower;
        this.noHit = true;
        super.setInfinitePickupDelay();
        this.damage = damage;
    }
    
    public EntityItemProjectile(LivingEntity thrower, ItemStack stack) 
    {
        this(thrower, stack, -1);
    }

    public LivingEntity getItemThrower() 
    {
        return thrower;
    }

    public void setHeadingFromThrower(Entity thrower, float rotationPitchIn, float rotationYawIn, float pitchOffset, float velocity, float inaccuracy)
    {
        float f = -MathHelper.sin(rotationYawIn * 0.017453292F) * MathHelper.cos(rotationPitchIn * 0.017453292F);
        float f1 = -MathHelper.sin((rotationPitchIn + pitchOffset) * 0.017453292F);
        float f2 = MathHelper.cos(rotationYawIn * 0.017453292F) * MathHelper.cos(rotationPitchIn * 0.017453292F);
        this.shoot(f, f1, f2, velocity, inaccuracy);

        double y = thrower.onGround ? 0.0 : thrower.getMotion().getY();
        this.setMotion(this.getMotion().add(thrower.getMotion().getX(), y, thrower.getMotion().getZ()));
    }
    
    public void shoot(Entity shooter, float pitch, float yaw, float velocity, float inaccuracy)
    {
        float f = -MathHelper.sin(yaw * 0.017453292F) * MathHelper.cos(pitch * 0.017453292F);
        float f1 = -MathHelper.sin(pitch * 0.017453292F);
        float f2 = MathHelper.cos(yaw * 0.017453292F) * MathHelper.cos(pitch * 0.017453292F);
        this.shoot(f, f1, f2, velocity, inaccuracy);
        
        double y = shooter.onGround ? 0.0 : shooter.getMotion().getY();
        this.setMotion(this.getMotion().add(shooter.getMotion().getX(), y, shooter.getMotion().getZ()));
    }
    
    @Override
    public void shoot(double x, double y, double z, float velocity, float inaccuracy)
    {
        float f = MathHelper.sqrt(x * x + y * y + z * z);
        x = x / (double)f;
        y = y / (double)f;
        z = z / (double)f;
        x = x + this.rand.nextGaussian() * 0.0075d * (double)inaccuracy;
        y = y + this.rand.nextGaussian() * 0.0075d * (double)inaccuracy;
        z = z + this.rand.nextGaussian() * 0.0075d * (double)inaccuracy;
        x = x * (double)velocity;
        y = y * (double)velocity;
        z = z * (double)velocity;
        this.setMotion(x, y, z);
        float f1 = MathHelper.sqrt(x * x + z * z);
        this.rotationYaw = (float)(MathHelper.atan2(x, z) * (180D / Math.PI));
        this.rotationPitch = (float)(MathHelper.atan2(y, (double)f1) * (180D / Math.PI));
        this.prevRotationYaw = this.rotationYaw;
        this.prevRotationPitch = this.rotationPitch;
    }

    @Override
    public void tick() 
    {
        super.tick();
        if(noHit)
        {
            if(this.onGround)
            {
                noHit = false;
                this.setDefaultPickupDelay();
                return;
            }
            
            float fw = this.getWidth() / 2;
            float fh = this.getHeight() / 2;
            List<Entity> list = this.world.getEntitiesWithinAABBExcludingEntity(this, 
                    new AxisAlignedBB(prevPosX, prevPosY, prevPosZ, posX, posY, posZ).expand(fw, fh, fw));
            if(list.isEmpty())
            {
                return;
            }
            
            Vec3d oldV = new Vec3d(this.prevPosX, prevPosY, prevPosZ);
            Vec3d newV = new Vec3d(this.posX, this.posY, this.posZ);          
            list.removeIf(ent -> 
            {
                // this prevents the projectile from hitting its shooter during
                // the first ticks
                if(ent == thrower && ReflectionUtils.getAge(this) < 5)
                {
                    return true;
                }
                // size of the projectile is 0.25 x 0.25
                return !ent.getBoundingBox().grow(0.25f).intersects(oldV, newV);
            });
            if(!list.isEmpty())
            {
                noHit = false;
                this.setDefaultPickupDelay();
                onImpact(list);
            }
        }
    }

    protected void onImpact(List<Entity> list)
    {
        if(damage == -1)
        {
            if(KajetansMod.scripts != null && thrower instanceof PlayerEntity)
            {
                ScriptEvents.onEntityItemProjectileHit(this, (PlayerEntity) thrower, this.getItem(), list);
            }
        }
        else
        {
            list.forEach(ent -> ent.attackEntityFrom(DamageSource.causeThrownDamage(this, thrower), damage));
        }
    }
}