import { serveDir } from "@std/http/file-server";
import { CHUNK_HEIGHT } from "$/common/constants.ts";
import {
	BlockChange,
	ClientMessage,
	MAX_CHAT_LENGTH,
	MAX_NAME_LENGTH,
	PlayerInfo,
	ServerMessage,
} from "$/common/protocol.ts";

const PORT = Number(Deno.env.get("PORT") ?? 8000);
const WORLD_FILE = Deno.env.get("WORLD_FILE") ?? "world.json";
const STATIC_ROOT = "build";
const SAVE_INTERVAL_MS = 30_000;
const MAX_MESSAGE_SIZE = 4096;
// how far from a player a block can be changed, a bit more than the client's reach
const MAX_REACH = 8;

const BLOCK_ID_PATTERN = /^[a-z0-9_]+:[a-z0-9_]+$/;

interface SavedWorld {
	seed: string;
	changes: BlockChange[];
}

interface Client {
	socket: WebSocket;
	player?: PlayerInfo;
}

// the server doesnt generate terrain, clients do that from the seed
// we only keep track of what players changed on top of it
class ServerWorld {
	seed: string;
	changes = new Map<string, BlockChange>();
	dirty = false;

	constructor(seed: string) {
		this.seed = seed;
	}

	set_block(x: number, y: number, z: number, id: string) {
		this.changes.set(`${x},${y},${z}`, [x, y, z, id]);
		this.dirty = true;
	}

	static load(path: string): ServerWorld {
		try {
			const saved: SavedWorld = JSON.parse(Deno.readTextFileSync(path));
			const world = new ServerWorld(saved.seed);
			for (const [x, y, z, id] of saved.changes) {
				world.changes.set(`${x},${y},${z}`, [x, y, z, id]);
			}
			console.log(`Loaded ${path} (${world.changes.size} block changes)`);
			return world;
		} catch (e) {
			if (!(e instanceof Deno.errors.NotFound)) {
				throw e;
			}
			const world = new ServerWorld(Deno.env.get("SEED") ?? crypto.randomUUID());
			world.dirty = true;
			console.log(`Created new world with seed ${world.seed}`);
			return world;
		}
	}

	save(path: string) {
		if (!this.dirty) {
			return;
		}
		const saved: SavedWorld = { seed: this.seed, changes: [...this.changes.values()] };
		// write then rename so a crash mid write doesnt eat the world
		Deno.writeTextFileSync(`${path}.tmp`, JSON.stringify(saved));
		Deno.renameSync(`${path}.tmp`, path);
		this.dirty = false;
	}
}

const world = ServerWorld.load(WORLD_FILE);
const clients = new Set<Client>();

function send(client: Client, message: ServerMessage) {
	if (client.socket.readyState === WebSocket.OPEN) {
		client.socket.send(JSON.stringify(message));
	}
}

function broadcast(message: ServerMessage, except?: Client) {
	const data = JSON.stringify(message);
	for (const client of clients) {
		if (client !== except && client.player && client.socket.readyState === WebSocket.OPEN) {
			client.socket.send(data);
		}
	}
}

function is_number(value: unknown): value is number {
	return typeof value === "number" && Number.isFinite(value);
}

function is_int(value: unknown): value is number {
	return Number.isInteger(value);
}

function clean_name(name: unknown): string {
	const cleaned = typeof name === "string" ? name.replace(/[^A-Za-z0-9_]/g, "").slice(0, MAX_NAME_LENGTH) : "";
	const base = cleaned || `player${Math.floor(Math.random() * 10000)}`;

	// make it unique
	const taken = new Set([...clients].map((c) => c.player?.name));
	let final = base;
	let i = 2;
	while (taken.has(final)) {
		final = `${base}${i}`;
		i += 1;
	}
	return final;
}

function handle_message(client: Client, message: ClientMessage) {
	if (!client.player) {
		if (message.type !== "hello") {
			return;
		}
		const player: PlayerInfo = {
			id: crypto.randomUUID(),
			name: clean_name(message.name),
			x: 0,
			y: 100,
			z: 0,
			yaw: 0,
			pitch: 0,
		};
		send(client, {
			type: "welcome",
			id: player.id,
			seed: world.seed,
			players: [...clients].flatMap((c) => c.player ? [c.player] : []),
			changes: [...world.changes.values()],
		});
		client.player = player;
		broadcast({ type: "player_join", player }, client);
		broadcast({ type: "chat", text: `${player.name} joined` });
		console.log(`${player.name} joined (${clients.size} online)`);
		return;
	}

	const player = client.player;

	switch (message.type) {
		case "move": {
			const { x, y, z, yaw, pitch } = message;
			if (![x, y, z, yaw, pitch].every(is_number)) {
				return;
			}
			Object.assign(player, { x, y, z, yaw, pitch });
			broadcast({ type: "player_move", id: player.id, x, y, z, yaw, pitch }, client);
			break;
		}
		case "set_block": {
			const { x, y, z, id } = message;
			if (!is_int(x) || !is_int(y) || !is_int(z) || y < 0 || y >= CHUNK_HEIGHT) {
				return;
			}
			if (typeof id !== "string" || !BLOCK_ID_PATTERN.test(id)) {
				return;
			}
			const dx = x + 0.5 - player.x;
			const dy = y + 0.5 - (player.y + 1.69);
			const dz = z + 0.5 - player.z;
			if (dx * dx + dy * dy + dz * dz > MAX_REACH * MAX_REACH) {
				return;
			}
			world.set_block(x, y, z, id);
			broadcast({ type: "set_block", x, y, z, id }, client);
			break;
		}
		case "chat": {
			if (typeof message.text !== "string") {
				return;
			}
			const text = message.text.trim().slice(0, MAX_CHAT_LENGTH);
			if (text.length === 0) {
				return;
			}
			console.log(`<${player.name}> ${text}`);
			broadcast({ type: "chat", from: player.name, text });
			break;
		}
	}
}

function handle_socket(socket: WebSocket) {
	const client: Client = { socket };

	socket.addEventListener("open", () => {
		clients.add(client);
	});

	socket.addEventListener("message", (event) => {
		if (typeof event.data !== "string" || event.data.length > MAX_MESSAGE_SIZE) {
			return;
		}
		let message: ClientMessage;
		try {
			message = JSON.parse(event.data);
		} catch {
			return;
		}
		if (typeof message !== "object" || message === null) {
			return;
		}
		handle_message(client, message);
	});

	socket.addEventListener("close", () => {
		clients.delete(client);
		if (client.player) {
			broadcast({ type: "player_leave", id: client.player.id });
			broadcast({ type: "chat", text: `${client.player.name} left` });
			console.log(`${client.player.name} left (${clients.size} online)`);
		}
	});
}

setInterval(() => world.save(WORLD_FILE), SAVE_INTERVAL_MS);

function shutdown() {
	console.log("Saving world...");
	world.save(WORLD_FILE);
	Deno.exit(0);
}
Deno.addSignalListener("SIGINT", shutdown);
if (Deno.build.os !== "windows") {
	Deno.addSignalListener("SIGTERM", shutdown);
}

Deno.serve({ port: PORT, onListen: ({ port }) => console.log(`bworld server on http://localhost:${port}/`) }, (req) => {
	const url = new URL(req.url);

	if (url.pathname === "/ws") {
		if (req.headers.get("upgrade")?.toLowerCase() !== "websocket") {
			return new Response("Expected a websocket", { status: 426 });
		}
		const { socket, response } = Deno.upgradeWebSocket(req);
		handle_socket(socket);
		return response;
	}

	if (url.pathname === "/") {
		return Response.redirect(new URL("/client/", url), 302);
	}

	return serveDir(req, { fsRoot: STATIC_ROOT, quiet: true });
});