import { EverythingRegistry, ItemRegistry } from "$/common/everything_registry.ts";

// how item stacks are saved and sent over the network
export interface ItemData {
	id: string;
	count: number;
	data?: unknown;
}

export class ItemStack<T = unknown | undefined> {
	type_id: string;
	amount: number;
	max_amount: number;
	data?: T;

	constructor(type_id: string | string, amount: number = 1, max_amount: number = 64) {
		this.type_id = type_id;
		this.amount = amount;
		this.max_amount = max_amount;
		this.data = undefined;
		const item_info = EverythingRegistry.get<ItemRegistry>("items", type_id);
		if (item_info?.on_create) {
			item_info.on_create(this);
		}
	}

	clone(): ItemStack {
		const item = new ItemStack(this.type_id, this.amount, this.max_amount);
		item.data = structuredClone(this.data);
		return item;
	}

	to_data(): ItemData {
		return this.data === undefined
			? { id: this.type_id, count: this.amount }
			: { id: this.type_id, count: this.amount, data: this.data };
	}

	static from_data(data: ItemData): ItemStack {
		const item = new ItemStack(data.id, data.count);
		if (data.data !== undefined) {
			item.data = data.data;
		}
		return item;
	}
}

export class ContainerSlot {
	#item_stack: ItemStack | undefined;

	has_item() {
		return this.#item_stack !== undefined;
	}

	set_item(item_stack: ItemStack | undefined) {
		if ((item_stack?.amount ?? 0) <= 0) {
			item_stack = undefined;
		}
		this.#item_stack = item_stack;
	}

	get_item() {
		return this.#item_stack;
	}

	get type_id() {
		return this.#item_stack?.type_id;
	}

	set amount(new_amount: number) {
		if (this.#item_stack) {
			this.#item_stack.amount = new_amount;
			if (this.#item_stack.amount <= 0) {
				this.#item_stack = undefined;
			}
		}
	}

	get amount(): number | undefined {
		return this.#item_stack?.amount;
	}

	get max_amount() {
		return this.#item_stack?.max_amount;
	}
}

export class Container {
	#slots: ContainerSlot[] = [];
	readonly size: number;

	constructor(size: number) {
		this.size = size;
		for (let i = 0; i < size; i += 1) {
			this.#slots.push(new ContainerSlot());
		}
	}

	// returns how many items didn't fit
	add_item(item_stack: ItemStack): number {
		for (const slot of this.#slots.filter((slot) => slot.has_item())) {
			const slot_item = slot.get_item()!;
			if (slot_item.type_id === item_stack.type_id) {
				const missing = slot_item.max_amount - slot_item.amount;
				const adding = Math.min(missing, item_stack.amount);
				slot_item.amount += adding;
				item_stack.amount -= adding;
				if (item_stack.amount === 0) {
					return 0;
				}
			}
		}
		for (const slot of this.#slots) {
			if (!slot.has_item()) {
				slot.set_item(item_stack);
				return 0;
			}
		}
		// TODO: drop item on ground
		return item_stack.amount;
	}

	get_item(slot: number): ItemStack | undefined {
		return this.#slots[slot]?.get_item();
	}

	get_slot(slot: number): ContainerSlot {
		return this.#slots[slot];
	}

	set_item(slot: number, item: ItemStack | undefined) {
		this.#slots[slot].set_item(item);
	}

	to_data(): (ItemData | null)[] {
		return this.#slots.map((slot) => slot.get_item()?.to_data() ?? null);
	}

	load(data: (ItemData | null)[]) {
		for (let i = 0; i < this.size; i += 1) {
			const item = data[i];
			this.#slots[i].set_item(item ? ItemStack.from_data(item) : undefined);
		}
	}

	clear() {
		for (const slot of this.#slots) {
			slot.set_item(undefined);
		}
	}
}

// the item a player is carrying around with the mouse in an inventory screen
export interface Cursor {
	item: ItemStack | undefined;
}

export const LEFT_CLICK = 0;
export const RIGHT_CLICK = 2;

// what clicking a normal slot does, the server runs this for real and clients run it to predict
export function click_slot(container: Container, index: number, cursor: Cursor, button: number) {
	if (button === LEFT_CLICK) {
		left_click(container, index, cursor);
	} else if (button === RIGHT_CLICK) {
		right_click(container, index, cursor);
	}
	if (cursor.item && cursor.item.amount <= 0) {
		cursor.item = undefined;
	}
}

function swap_with_cursor(container: Container, index: number, cursor: Cursor) {
	const slot = container.get_slot(index);
	const original = cursor.item;
	cursor.item = slot.get_item();
	slot.set_item(original);
}

function left_click(container: Container, index: number, cursor: Cursor) {
	const holding = cursor.item;
	const slot = container.get_slot(index);
	const slot_item = slot.get_item();

	// if you aren't holding anything
	// "swap" with nothing on your hand (pick it up)
	if (!holding) {
		swap_with_cursor(container, index, cursor);
		return;
	}

	// if you are holding something and slot type equals holding type
	// try to add to stack
	if (slot_item && slot.type_id === holding.type_id) {
		const space_left = slot.max_amount! - slot_item.amount;
		const amount_to_add = Math.min(space_left, holding.amount);

		slot_item.amount += amount_to_add;
		holding.amount -= amount_to_add;

		return;
	}

	// if something on hand but not the same
	// swap
	swap_with_cursor(container, index, cursor);
}

function right_click(container: Container, index: number, cursor: Cursor) {
	const holding = cursor.item;
	const slot = container.get_slot(index);
	const slot_item = slot.get_item();

	// if holding something
	if (holding) {
		// and slot type equals holding type
		// add 1 to matching stack
		if (slot_item && slot.type_id === holding.type_id) {
			if (slot_item.amount < slot_item.max_amount) {
				slot_item.amount += 1;
				holding.amount -= 1;
			}
			return;
		}

		// place 1 into empty slot
		if (!slot_item) {
			const new_item = holding.clone();
			new_item.amount = 1;
			slot.set_item(new_item);
			holding.amount -= 1;
			return;
		}

		// if something on hand but not the same
		// swap
		swap_with_cursor(container, index, cursor);
		return;
	}

	// if player is holding nothing and clicks nothing, nothing happens
	if (!slot_item) {
		return;
	}

	// pick up half of the stack
	const original_amount = slot_item.amount;
	const half = Math.floor(original_amount / 2);

	const picked_up = slot_item.clone();
	picked_up.amount = original_amount - half;
	cursor.item = picked_up;

	slot.amount = half;
}

// output slots (furnace result, crafting result) can only be taken from, all at once
// returns whether it was taken
export function take_output(item: ItemStack, cursor: Cursor): boolean {
	const holding = cursor.item;
	if (!holding) {
		cursor.item = item.clone();
		return true;
	}
	if (holding.type_id === item.type_id && holding.max_amount - holding.amount >= item.amount) {
		holding.amount += item.amount;
		return true;
	}
	return false;
}