import { ItemStack } from "$/common/inventory.ts";
import type { EntityInfo } from "$/common/protocol.ts";
import type { ClientLevel } from "../level/client_level.ts";
import { Entity } from "./entity.ts";

// how many ticks a server position takes to reach, like minecraft's lerpTo
const LERP_TICKS = 3;
// how many ticks it takes to fly into whoever picked it up
const PICKUP_TICKS = 3;

// an item lying on the ground. the server simulates it, this only moves where it's told and spins
export class ItemEntity extends Entity {
	item: ItemStack;
	// ticks since it showed up, for spinning and bobbing
	age = 0;
	// so items dropped together don't spin in step
	readonly bob_offset = Math.random() * Math.PI * 2;

	#target_x: number;
	#target_y: number;
	#target_z: number;
	#lerp_ticks = 0;

	// who's picking it up, and for how many ticks it has been flying to them
	#picked_up_by: Entity | undefined;
	#pickup_age = 0;

	constructor(level: ClientLevel, info: EntityInfo) {
		super(level, info.id, 0.25, 0.25, 0.125);
		this.item = ItemStack.from_data(info.item);
		this.set_position(info.x, info.y, info.z);
		this.#target_x = info.x;
		this.#target_y = info.y;
		this.#target_z = info.z;
	}

	lerp_to(x: number, y: number, z: number) {
		this.#target_x = x;
		this.#target_y = y;
		this.#target_z = z;
		this.#lerp_ticks = LERP_TICKS;
	}

	// it already went into their inventory on the server, this is only the animation
	pick_up(by: Entity) {
		this.#picked_up_by = by;
	}

	tick() {
		this.age += 1;

		if (this.#picked_up_by) {
			this.#pickup_age += 1;
			if (this.#pickup_age >= PICKUP_TICKS) {
				this.level.remove_entity(this.id);
			}
			return;
		}

		if (this.#lerp_ticks > 0) {
			this.x += (this.#target_x - this.x) / this.#lerp_ticks;
			this.y += (this.#target_y - this.y) / this.#lerp_ticks;
			this.z += (this.#target_z - this.z) / this.#lerp_ticks;
			this.#lerp_ticks -= 1;
		}
	}

	// while being picked up it speeds towards the middle of whoever took it, like minecraft's ItemPickupParticle
	override render_position(partial_tick: number) {
		const position = super.render_position(partial_tick);
		const by = this.#picked_up_by;
		if (!by) {
			return position;
		}
		const target = by.render_position(partial_tick);
		const t = Math.min(1, (this.#pickup_age + partial_tick) / PICKUP_TICKS) ** 2;
		return {
			x: position.x + (target.x - position.x) * t,
			y: position.y + (target.y + 0.5 - position.y) * t,
			z: position.z + (target.z - position.z) * t,
		};
	}
}