Unicopia/src/main/java/com/minelittlepony/unicopia/item/SpellbookItem.java

package com.minelittlepony.unicopia.item;

import javax.annotation.Nullable;

import com.minelittlepony.unicopia.EquinePredicates;
import com.minelittlepony.unicopia.entity.SpellbookEntity;
import com.minelittlepony.unicopia.entity.UEntities;
import com.minelittlepony.unicopia.magic.Dispensable;

import net.minecraft.block.DispenserBlock;
import net.minecraft.entity.player.PlayerEntity;
import net.minecraft.item.BookItem;
import net.minecraft.item.Item;
import net.minecraft.item.ItemGroup;
import net.minecraft.item.ItemStack;
import net.minecraft.item.ItemUsageContext;
import net.minecraft.util.ActionResult;
import net.minecraft.util.TypedActionResult;
import net.minecraft.util.math.BlockPointer;
import net.minecraft.util.math.BlockPos;
import net.minecraft.util.math.Direction;
import net.minecraft.world.World;

public class SpellbookItem extends BookItem implements Dispensable {

    public SpellbookItem() {
        super(new Item.Settings()
                .maxCount(1)
                .group(ItemGroup.BREWING));

        setDispenseable();
    }

    @Override
    public ActionResult useOnBlock(ItemUsageContext context) {

        @Nullable
        PlayerEntity player = context.getPlayer();

        if (!context.getWorld().isClient && EquinePredicates.MAGI.test(player)) {
            BlockPos pos = context.getBlockPos().offset(context.getSide());

            double diffX = player.x - (pos.getX() + 0.5);
            double diffZ = player.z - (pos.getZ() + 0.5);
            float yaw = (float)Math.toDegrees(Math.atan2(diffZ, diffX) + Math.PI);

            placeBook(context.getWorld(), pos.getX(), pos.getY(), pos.getZ(), yaw);

            if (!player.abilities.creativeMode) {
                player.getStackInHand(context.getHand()).decrement(1);
            }

            return ActionResult.SUCCESS;
        }
        return ActionResult.PASS;
    }

    private static void placeBook(World world, int x, int y, int z, float yaw) {
        SpellbookEntity book = UEntities.SPELLBOOK.create(world);

        book.setPositionAndAngles(x + 0.5, y, z + 0.5, yaw, 0);
        //book.renderYawOffset = 0;
        book.prevYaw = yaw;

        world.spawnEntity(book);
    }

    @Override
    public TypedActionResult<ItemStack> dispenseStack(BlockPointer source, ItemStack stack) {
        Direction facing = source.getBlockState().get(DispenserBlock.FACING);
        BlockPos pos = source.getBlockPos().offset(facing);

        //0deg == SOUTH
        //90deg == WEST
        //180deg == NORTH
        //270deg == EAST

        /*switch (facing) {
        case NORTH: yaw -= 90; break;
        case SOUTH: yaw += 90; break;
        case EAST: yaw += 180; break;
        default:
        }*/

        int yaw = facing.getOpposite().getHorizontal() * 90;
        placeBook(source.getWorld(), pos.getX(), pos.getY(), pos.getZ(), yaw);
        stack.decrement(1);

        return new TypedActionResult<>(ActionResult.SUCCESS, stack);
    }
}