Unicopia/src/main/java/com/minelittlepony/util/ProjectileUtil.java

package com.minelittlepony.util;

import javax.annotation.Nullable;

import net.minecraft.entity.Entity;
import net.minecraft.entity.IProjectile;
import net.minecraft.entity.projectile.EntityArrow;
import net.minecraft.entity.projectile.EntityFireball;
import net.minecraft.entity.projectile.EntityLlamaSpit;
import net.minecraft.entity.projectile.EntityThrowable;
import net.minecraft.util.math.Vec3d;

public class ProjectileUtil {

	/**
	 * Checks if the given entity is a projectile.
	 */
	public static boolean isProjectile(Entity e) {
		return e instanceof IProjectile
		        || e instanceof EntityFireball;
	}

	/**
	 * Checks if an entity is a thrown projectile.
	 */
	public static boolean isThrowable(Entity e) {
	    return e instanceof EntityThrowable ||
                e instanceof EntityArrow ||
                e instanceof EntityFireball;
	}

	/**
	 * Checks if the given projectile was thrown by the given entity
	 */
	@SuppressWarnings("unchecked")
	public static <T extends Entity> boolean isProjectileThrownBy(Entity throwable, @Nullable T e) {
		if (e == null || !isThrowable(throwable)) {
		    return false;
		}

		return e.equals(getThrowingEntity(throwable));
	}

	/**
	 * Gets the thrower for a projectile or null
	 */
	@Nullable
	@SuppressWarnings("unchecked")
	public static <T extends Entity> T getThrowingEntity(Entity throwable) {

	    if (throwable instanceof EntityArrow) {
	        return (T)((EntityArrow) throwable).shootingEntity;
	    }

	    if (throwable instanceof EntityFireball) {
            return (T)((EntityFireball) throwable).shootingEntity;
        }

	    if (throwable instanceof EntityLlamaSpit) {
           return (T)((EntityLlamaSpit) throwable).owner;
	    }

        if (throwable instanceof EntityThrowable) {
            return (T)((EntityThrowable) throwable).getThrower();
        }

		return null;
	}

	   /**
     * Sets the velocity and heading for a projectile.
     *
     * @param throwable     The projectile
     * @param heading       The directional heaving vector
     * @param velocity      Velocity
     * @param inaccuracy    Inaccuracy
     * @return              True the projectile's heading was set, false otherwise
     */
	public static void setThrowableHeading(Entity throwable, Vec3d heading, float velocity, float inaccuracy) {

		if (throwable instanceof IProjectile) {
			((IProjectile)throwable).shoot(heading.x, heading.y, heading.z, velocity, inaccuracy);
		} else {
		    heading = heading.normalize().scale(velocity);

	        throwable.addVelocity(heading.x - throwable.motionX, heading.y - throwable.motionY, heading.z - throwable.motionZ);
		}
	}
}