Code/net/minecraft/world/inventory/LecternMenu.java

package net.minecraft.world.inventory;

import net.minecraft.world.Container;
import net.minecraft.world.SimpleContainer;
import net.minecraft.world.entity.player.Player;
import net.minecraft.world.item.ItemStack;

public class LecternMenu extends AbstractContainerMenu {
    private static final int DATA_COUNT = 1;
    private static final int SLOT_COUNT = 1;
    public static final int BUTTON_PREV_PAGE = 1;
    public static final int BUTTON_NEXT_PAGE = 2;
    public static final int BUTTON_TAKE_BOOK = 3;
    public static final int BUTTON_PAGE_JUMP_RANGE_START = 100;
    private final Container lectern;
    private final ContainerData lecternData;

    public LecternMenu(int p_39822_) {
        this(p_39822_, new SimpleContainer(1), new SimpleContainerData(1));
    }

    public LecternMenu(int p_39824_, Container p_39825_, ContainerData p_39826_) {
        super(MenuType.LECTERN, p_39824_);
        checkContainerSize(p_39825_, 1);
        checkContainerDataCount(p_39826_, 1);
        this.lectern = p_39825_;
        this.lecternData = p_39826_;
        this.addSlot(new Slot(p_39825_, 0, 0, 0) {
            @Override
            public void setChanged() {
                super.setChanged();
                LecternMenu.this.slotsChanged(this.container);
            }
        });
        this.addDataSlots(p_39826_);
    }

    @Override
    public boolean clickMenuButton(Player p_39833_, int p_39834_) {
        if (p_39834_ >= 100) {
            int k = p_39834_ - 100;
            this.setData(0, k);
            return true;
        } else {
            switch (p_39834_) {
                case 1:
                    int j = this.lecternData.get(0);
                    this.setData(0, j - 1);
                    return true;
                case 2:
                    int i = this.lecternData.get(0);
                    this.setData(0, i + 1);
                    return true;
                case 3:
                    if (!p_39833_.mayBuild()) {
                        return false;
                    }

                    ItemStack itemstack = this.lectern.removeItemNoUpdate(0);
                    this.lectern.setChanged();
                    if (!p_39833_.getInventory().add(itemstack)) {
                        p_39833_.drop(itemstack, false);
                    }

                    return true;
                default:
                    return false;
            }
        }
    }

    @Override
    public ItemStack quickMoveStack(Player p_219987_, int p_219988_) {
        return ItemStack.EMPTY;
    }

    @Override
    public void setData(int p_39828_, int p_39829_) {
        super.setData(p_39828_, p_39829_);
        this.broadcastChanges();
    }

    @Override
    public boolean stillValid(Player p_39831_) {
        return this.lectern.stillValid(p_39831_);
    }

    public ItemStack getBook() {
        return this.lectern.getItem(0);
    }

    public int getPage() {
        return this.lecternData.get(0);
    }
}