/// <reference lib="webworker" />

import type { BlockRegistry, RenderLayer } from "$/common/everything_registry.ts";
import { AIR, type SpriteRegion } from "$/common/constants.ts";
import type { Texture } from "../renderer/types.ts";
import type { FromChunkWorker, ToChunkWorker } from "./chunk_messages.ts";
import { generate_raw_chunk, WorldgenSetup } from "$/common/generation.ts";
import { load_worldgen } from "$/common/worldgen_loader.ts";
import { default_block_value } from "$/common/utils.ts";
import {
	choose_sort_type,
	FACE_NORMALS,
	quad_indices,
	quad_planes,
	sort_by_distance,
	sort_quads,
} from "./translucent_sort.ts";

const pad = 0.5;

function push_vertex(
	vertices: Float32Array,
	i: number,
	px: number,
	py: number,
	pz: number,
	u: number,
	v: number,
	r: number,
	g: number,
	b: number,
	a: number,
) {
	vertices[i++] = px;
	vertices[i++] = py;
	vertices[i++] = pz;
	vertices[i++] = u;
	vertices[i++] = v;
	vertices[i++] = r;
	vertices[i++] = g;
	vertices[i++] = b;
	vertices[i++] = a;

	return i;
}

export function push_front_face(
	vertices: Float32Array,
	i: number,
	texture: Texture,
	x: number,
	y: number,
	z: number,
	sx: number,
	sy: number,
	sw: number,
	sh: number,
	r = 1,
	g = 1,
	b = 1,
	a = 1,
) {
	const x2 = x + 1;
	const y2 = y + 1;
	const z2 = z + 1;

	const u0 = (sx + pad) / texture.width;
	const v0 = (sy + pad) / texture.height;
	const u1 = (sx + sw - pad) / texture.width;
	const v1 = (sy + sh - pad) / texture.height;

	i = push_vertex(vertices, i, x, y, z2, u0, v1, r, g, b, a);
	i = push_vertex(vertices, i, x2, y, z2, u1, v1, r, g, b, a);
	i = push_vertex(vertices, i, x2, y2, z2, u1, v0, r, g, b, a);
	i = push_vertex(vertices, i, x, y2, z2, u0, v0, r, g, b, a);

	return i;
}

export function push_back_face(
	vertices: Float32Array,
	i: number,
	texture: Texture,
	x: number,
	y: number,
	z: number,
	sx: number,
	sy: number,
	sw: number,
	sh: number,
	r = 1,
	g = 1,
	b = 1,
	a = 1,
) {
	const x2 = x + 1;
	const y2 = y + 1;

	const u0 = (sx + pad) / texture.width;
	const v0 = (sy + pad) / texture.height;
	const u1 = (sx + sw - pad) / texture.width;
	const v1 = (sy + sh - pad) / texture.height;

	i = push_vertex(vertices, i, x2, y, z, u0, v1, r, g, b, a);
	i = push_vertex(vertices, i, x, y, z, u1, v1, r, g, b, a);
	i = push_vertex(vertices, i, x, y2, z, u1, v0, r, g, b, a);
	i = push_vertex(vertices, i, x2, y2, z, u0, v0, r, g, b, a);

	return i;
}

export function push_left_face(
	vertices: Float32Array,
	i: number,
	texture: Texture,
	x: number,
	y: number,
	z: number,
	sx: number,
	sy: number,
	sw: number,
	sh: number,
	r = 1,
	g = 1,
	b = 1,
	a = 1,
) {
	const y2 = y + 1;
	const z2 = z + 1;

	const u0 = (sx + pad) / texture.width;
	const v0 = (sy + pad) / texture.height;
	const u1 = (sx + sw - pad) / texture.width;
	const v1 = (sy + sh - pad) / texture.height;

	i = push_vertex(vertices, i, x, y, z, u0, v1, r, g, b, a);
	i = push_vertex(vertices, i, x, y, z2, u1, v1, r, g, b, a);
	i = push_vertex(vertices, i, x, y2, z2, u1, v0, r, g, b, a);
	i = push_vertex(vertices, i, x, y2, z, u0, v0, r, g, b, a);

	return i;
}

export function push_right_face(
	vertices: Float32Array,
	i: number,
	texture: Texture,
	x: number,
	y: number,
	z: number,
	sx: number,
	sy: number,
	sw: number,
	sh: number,
	r = 1,
	g = 1,
	b = 1,
	a = 1,
) {
	const x2 = x + 1;
	const y2 = y + 1;
	const z2 = z + 1;

	const u0 = (sx + pad) / texture.width;
	const v0 = (sy + pad) / texture.height;
	const u1 = (sx + sw - pad) / texture.width;
	const v1 = (sy + sh - pad) / texture.height;

	i = push_vertex(vertices, i, x2, y, z2, u0, v1, r, g, b, a);
	i = push_vertex(vertices, i, x2, y, z, u1, v1, r, g, b, a);
	i = push_vertex(vertices, i, x2, y2, z, u1, v0, r, g, b, a);
	i = push_vertex(vertices, i, x2, y2, z2, u0, v0, r, g, b, a);

	return i;
}

export function push_top_face(
	vertices: Float32Array,
	i: number,
	texture: Texture,
	x: number,
	y: number,
	z: number,
	sx: number,
	sy: number,
	sw: number,
	sh: number,
	r = 1,
	g = 1,
	b = 1,
	a = 1,
) {
	const x2 = x + 1;
	const z2 = z + 1;
	const y2 = y + 1;

	const u0 = (sx + pad) / texture.width;
	const v0 = (sy + pad) / texture.height;
	const u1 = (sx + sw - pad) / texture.width;
	const v1 = (sy + sh - pad) / texture.height;

	i = push_vertex(vertices, i, x, y2, z2, u0, v1, r, g, b, a);
	i = push_vertex(vertices, i, x2, y2, z2, u1, v1, r, g, b, a);
	i = push_vertex(vertices, i, x2, y2, z, u1, v0, r, g, b, a);
	i = push_vertex(vertices, i, x, y2, z, u0, v0, r, g, b, a);

	return i;
}

export function push_bottom_face(
	vertices: Float32Array,
	i: number,
	texture: Texture,
	x: number,
	y: number,
	z: number,
	sx: number,
	sy: number,
	sw: number,
	sh: number,
	r = 1,
	g = 1,
	b = 1,
	a = 1,
) {
	const x2 = x + 1;
	const z2 = z + 1;

	const u0 = (sx + pad) / texture.width;
	const v0 = (sy + pad) / texture.height;
	const u1 = (sx + sw - pad) / texture.width;
	const v1 = (sy + sh - pad) / texture.height;

	i = push_vertex(vertices, i, x, y, z, u0, v1, r, g, b, a);
	i = push_vertex(vertices, i, x2, y, z, u1, v1, r, g, b, a);
	i = push_vertex(vertices, i, x2, y, z2, u1, v0, r, g, b, a);
	i = push_vertex(vertices, i, x, y, z2, u0, v0, r, g, b, a);

	return i;
}

type TexturesInfo = Record<string, SpriteRegion>;

const CHUNK_SIZE = 16;
const CHUNK_HEIGHT = 128;
const TEXTURE_SIZE = 16;
const FLOATS_PER_QUAD = 4 * 9;

// same order as FACE_NORMALS in translucent_sort.ts
const FACES = ["top", "bottom", "front", "back", "left", "right"] as const;
const FACE_PUSHING_FUNCTIONS = [
	push_top_face,
	push_bottom_face,
	push_front_face,
	push_back_face,
	push_left_face,
	push_right_face,
] as const;

const SOLID = 0;
const CUTOUT = 1;
const TRANSLUCENT = 2;
const LAYER_IDS: Record<RenderLayer, number> = { solid: SOLID, cutout: CUTOUT, translucent: TRANSLUCENT };

let blocks_registry: BlockRegistry[] = [];
let block_ids: Record<string, number> = {};
// by numeric id, checked for every face
let block_layers = new Uint8Array(0);
let block_cull_same = new Uint8Array(0);
let textures_info: TexturesInfo = {};
let image: Texture;
let worldgen: WorldgenSetup | undefined;
// numeric id to what a generated block stores, with its default states. matches the server
let default_values: number[] = [];
// generating has to wait for mods' worldgen scripts, or this worker's terrain wouldn't match the server's
let worldgen_ready: Promise<void> = Promise.resolve();

self.onmessage = async (event: MessageEvent<ToChunkWorker>) => {
	const message = event.data;
	switch (message.type) {
		case "init":
			blocks_registry = message.blocks_registry;
			block_ids = message.block_ids;
			block_layers = Uint8Array.from(blocks_registry, (block) => LAYER_IDS[block?.render_layer ?? "solid"]);
			block_cull_same = Uint8Array.from(
				blocks_registry,
				(block) => (block?.cull_same ?? block?.render_layer === "translucent") ? 1 : 0,
			);
			textures_info = message.textures_info;
			image = message.image as Texture;
			default_values = blocks_registry.map((block, nid) => default_block_value(nid, block));
			worldgen_ready = load_worldgen(message.worldgen_scripts, message.ores).then((setup) => {
				worldgen = setup;
			});
			break;
		case "generate":
			await worldgen_ready;
			generate(message.chunk_x, message.chunk_z, message.seed);
			break;
		case "mesh": {
			const { solid, cutout, translucent } = make_chunk_mesh(
				message.chunk_x,
				message.chunk_z,
				message.padded_chunk,
				message.camera,
			);
			post(
				{
					type: "meshed",
					chunk_x: message.chunk_x,
					chunk_z: message.chunk_z,
					version: message.version,
					solid,
					cutout,
					translucent,
					camera: message.camera,
				},
				[
					solid.vertices.buffer,
					cutout.vertices.buffer,
					translucent.vertices.buffer,
					translucent.indices.buffer,
					translucent.centers.buffer,
					...translucent.planes.map((planes) => planes.buffer),
				],
			);
			break;
		}
		case "sort": {
			const [x, y, z] = message.camera;
			const indices = quad_indices(sort_by_distance(message.centers, message.centers.length / 3, x, y, z));
			post({
				type: "sorted",
				chunk_x: message.chunk_x,
				chunk_z: message.chunk_z,
				version: message.version,
				sort_version: message.sort_version,
				indices,
			}, [indices.buffer]);
			break;
		}
	}
};

function post(message: FromChunkWorker, transfer: Transferable[]) {
	self.postMessage(message, transfer);
}

function generate(chunk_x: number, chunk_z: number, seed: string) {
	const { blocks, spills } = generate_raw_chunk(chunk_x, chunk_z, seed, block_ids, worldgen, default_values);
	post({ type: "generated", chunk_x, chunk_z, blocks, spills }, [blocks.buffer, spills.buffer]);
}

// the rule vanilla minecraft (and so sodium) uses: solid neighbors hide a face, and some blocks
// hide faces between two of themselves
function show_face(block: number, neighbor: number) {
	if (neighbor === AIR) return true;
	// unloaded (VOID) or above/below the world
	const layer = block_layers[neighbor];
	if (layer === undefined || layer === SOLID) return false;
	return !(neighbor === block && block_cull_same[block]);
}

function make_chunk_mesh(chunk_x: number, chunk_z: number, padded_chunk: Uint32Array, camera: number[]) {
	const layers = [SOLID, CUTOUT, TRANSLUCENT].map(() => ({ vertices: new Float32Array(2048), floats: 0 }));
	// for sorting the translucent quads
	let centers = new Float32Array(256);
	let faces = new Uint8Array(256);

	const size = CHUNK_SIZE + 2;
	const layer_size = size * size;
	// where the neighbor on each face is in padded_chunk, same order as FACES
	const face_offsets = [layer_size, -layer_size, size, -size, -1, 1];

	for (let y = 0; y < CHUNK_HEIGHT; y++) {
		for (let z = 0; z < CHUNK_SIZE; z++) {
			for (let x = 0; x < CHUNK_SIZE; x++) {
				const index = y * layer_size + (z + 1) * size + (x + 1);
				const block_nid = padded_chunk[index];
				if (block_nid === AIR) continue;

				const block_info = blocks_registry[block_nid];
				const layer_id = block_layers[block_nid];
				const layer = layers[layer_id];
				const alpha = layer_id === TRANSLUCENT ? block_info.alpha ?? 1 : 1;

				const texture_ids = {
					top: "engine:missing",
					bottom: "engine:missing",
					front: "engine:missing",
					back: "engine:missing",
					left: "engine:missing",
					right: "engine:missing",
				};

				const textures = block_info.textures;
				if (!textures) throw new Error(`no textures for ${block_nid}`);

				if (typeof textures === "string") {
					texture_ids.top = textures;
					texture_ids.bottom = textures;
					texture_ids.front = textures;
					texture_ids.back = textures;
					texture_ids.left = textures;
					texture_ids.right = textures;
				} else if ("top" in textures && "bottom" in textures && "side" in textures) {
					texture_ids.top = textures.top;
					texture_ids.bottom = textures.bottom;
					texture_ids.front = textures.side;
					texture_ids.back = textures.side;
					texture_ids.left = textures.side;
					texture_ids.right = textures.side;
				} else if ("front" in textures && "side" in textures) {
					texture_ids.top = textures.side;
					texture_ids.bottom = textures.side;
					texture_ids.front = textures.front;
					texture_ids.back = textures.side;
					texture_ids.left = textures.side;
					texture_ids.right = textures.side;
				}

				const wx = chunk_x * CHUNK_SIZE + x;
				const wz = chunk_z * CHUNK_SIZE + z;

				for (let face = 0; face < 6; face++) {
					if (!show_face(block_nid, padded_chunk[index + face_offsets[face]])) {
						continue;
					}

					const region = textures_info[texture_ids[FACES[face]]];
					layer.vertices = ensure_capacity(layer.vertices, layer.floats + FLOATS_PER_QUAD);
					layer.floats = FACE_PUSHING_FUNCTIONS[face](
						layer.vertices,
						layer.floats,
						image,
						wx,
						y,
						wz,
						region.x * TEXTURE_SIZE,
						region.y * TEXTURE_SIZE,
						TEXTURE_SIZE,
						TEXTURE_SIZE,
						1,
						1,
						1,
						alpha,
					);

					if (layer_id === TRANSLUCENT) {
						const quad = layer.floats / FLOATS_PER_QUAD - 1;
						centers = ensure_capacity(centers, (quad + 1) * 3);
						faces = ensure_capacity(faces, quad + 1);
						const [nx, ny, nz] = FACE_NORMALS[face];
						centers[quad * 3] = wx + 0.5 + nx * 0.5;
						centers[quad * 3 + 1] = y + 0.5 + ny * 0.5;
						centers[quad * 3 + 2] = wz + 0.5 + nz * 0.5;
						faces[quad] = face;
					}
				}
			}
		}
	}

	const [solid, cutout, translucent] = layers.map((layer) => ({
		vertices: layer.vertices,
		quad_count: layer.floats / FLOATS_PER_QUAD,
	}));

	const quads = { centers, faces, count: translucent.quad_count };
	const sort_type = choose_sort_type(quads);
	const [camera_x, camera_y, camera_z] = camera;

	return {
		solid,
		cutout,
		translucent: {
			...translucent,
			indices: sort_quads(quads, sort_type, camera_x, camera_y, camera_z),
			sort_type,
			centers: centers.slice(0, quads.count * 3),
			planes: quad_planes(quads),
		},
	};
}

function ensure_capacity<T extends Float32Array<ArrayBuffer> | Uint8Array<ArrayBuffer>>(
	buffer: T,
	required: number,
): T {
	if (required <= buffer.length) return buffer;

	let new_length = buffer.length;
	while (new_length < required) {
		new_length *= 2;
	}

	const new_buffer = new (buffer.constructor as new (length: number) => T)(new_length);
	new_buffer.set(buffer as ArrayLike<number>);
	return new_buffer;
}