voxelforge/core/include/vf/ContainerMenu.h

#pragma once

#include <cstdint>
#include <vector>

#include "Container.h"
#include "Crafting.h"
#include "ItemStack.h"

namespace vf {

// A menu is the screen an open container puts in front of the player. It does
// not replace Container: a Container is still the storage that lives in the
// world and that hoppers, droppers and comparators read. The menu binds one for
// the duration of the screen, adds the player's own sections next to it, and
// gives every cell a role and an admission rule.

// What a slot is willing to accept. The result of a craft, a smelt or a trade
// takes Nothing, which is what makes it take-only.
struct SlotFilter {
    enum class Kind : uint8_t {
        Any,
        Nothing,
        Fuel,           // furnace fuel, per Crafting.h isFuel
        Smeltable,      // has a smelting recipe in the bound registry
        Lapis,          // enchanting table payment
        Enchantable,    // enchantabilityOf > 0
        Repairable,     // anvil input: tools carry durability, so they repair
        BrewIngredient, // the brewing ingredients that exist as items here
        Count
    };

    Kind kind = Kind::Any;

    // `registry` is only consulted by Smeltable; every other kind answers from
    // the item tables alone and accepts a null registry.
    bool accepts(const MetaStack& stack, const CraftingRegistry* registry) const;
};

const char* slotFilterKindName(SlotFilter::Kind kind);

// One storage cell: a stack plus a cap. `capacity` of zero defers to the item's
// own limit, anything else clamps below it (a brewing bottle holds exactly one).
struct StackSlot {
    MetaStack stack;
    int capacity = 0;

    bool empty() const { return stack.empty(); }
    int limitFor(const MetaStack& candidate) const;
    int room(const MetaStack& candidate) const;

    // Merges what fits from `incoming`, leaving the rest in it. Returns moved.
    int insert(MetaStack& incoming);
    MetaStack take(int amount);
    MetaStack takeAll();
    MetaStack swapWith(const MetaStack& incoming);
};

enum class MenuKind : uint8_t {
    PlayerInventory,
    CraftingTable,
    Chest,
    LargeChest,
    Furnace,
    BrewingStand,
    EnchantingTable,
    Anvil,
    Villager,
    Hopper,
    Count
};

const char* menuKindName(MenuKind kind);

struct MenuSlot {
    // Which part of the screen the slot belongs to. Shift-clicking moves items
    // between the container half and the player half, so the roles have to be
    // distinguishable at runtime, not just visually.
    enum class Role : uint8_t {
        Storage,        // the bound container, or the menu's own storage
        Inventory,      // the player's three rows
        Hotbar,         // the player's bottom row
        CraftInput,
        CraftResult,
        FuelInput,
        SmeltInput,
        SmeltOutput,
        BrewBottle,
        BrewIngredient,
        EnchantItem,
        EnchantLapis,
        AnvilInput,
        AnvilResult,
        TradeInput,
        TradeResult,
        OffHand,
        Count
    };

    StackSlot cell;
    Role role = Role::Storage;
    SlotFilter filter;
    // A take-only slot never accepts a placement, however empty it is.
    bool takeOnly = false;
    // Index into the bound Container, or -1 when the menu owns the stack.
    int backingIndex = -1;
};

const char* menuSlotRoleName(MenuSlot::Role role);

// Where each section starts and how long it is, so callers can iterate a
// section without knowing the slot order by heart.
struct MenuLayout {
    MenuKind kind = MenuKind::Chest;

    int storageFirst = -1;
    int storageCount = 0;
    int inventoryFirst = -1;
    int inventoryCount = 0;
    int hotbarFirst = -1;
    int hotbarCount = 0;
    int craftFirst = -1;
    int craftWidth = 0;
    int craftHeight = 0;
    int resultSlot = -1;
    int offHandSlot = -1;

    int totalSlots = 0;

    int craftCells() const { return craftWidth * craftHeight; }
    bool hasCrafting() const { return craftFirst >= 0 && craftCells() > 0; }
};

MenuLayout layoutFor(MenuKind kind);

constexpr int playerInventoryRows = 3;
constexpr int playerInventoryColumns = 9;
constexpr int playerInventorySlots = playerInventoryRows * playerInventoryColumns;
constexpr int playerHotbarSlots = 9;

class ContainerMenu;

// The crafting half of a menu, wired to the existing CraftingRegistry. It owns
// no stacks and no lifetime: it reads and writes the menu's craft slots in
// place, so the grid the player sees and the grid the recipe matcher sees are
// the same cells. A menu without a crafting section hands out a view whose
// cellCount is zero and whose operations therefore do nothing.
class CraftingView {
public:
    explicit CraftingView(ContainerMenu& menu);

    int width() const;
    int height() const;
    int cellCount() const;

    MetaStack& input(int x, int y);
    const MetaStack& input(int x, int y) const;
    MetaStack& inputAt(int cell);
    const MetaStack& inputAt(int cell) const;