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.EntityLivingBase;
import net.minecraft.entity.IProjectile;
import net.minecraft.entity.item.EntityItem;
import net.minecraft.entity.player.EntityPlayer;
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 EntityItem implements IProjectile
{
    private final EntityLivingBase thrower;
    private boolean noHit;
    private final float damage;

    public EntityItemProjectile(EntityLivingBase 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(EntityLivingBase thrower, ItemStack stack) 
    {
        this(thrower, stack, -1);
    }

    public EntityLivingBase getItemThrower() 
    {
        return thrower;
    }

    public void setHeadingFromThrower(Entity entityThrower, 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);
        this.motionX += entityThrower.motionX;
        this.motionZ += entityThrower.motionZ;

        if (!entityThrower.onGround)
        {
            this.motionY += entityThrower.motionY;
        }
    }
    
    @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.motionX = x;
        this.motionY = y;
        this.motionZ = 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 onUpdate() 
    {
        super.onUpdate();
        if(noHit)
        {
            if(this.onGround)
            {
                noHit = false;
                this.setDefaultPickupDelay();
                return;
            }
            
            float fw = this.width / 2;
            float fh = this.height / 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.getEntityBoundingBox().grow(0.125f).calculateIntercept(oldV, newV) == null;
            });
            if(!list.isEmpty())
            {
                noHit = false;
                this.setDefaultPickupDelay();
                onImpact(list);
            }
        }
    }

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