commit 28b026a6147a3e2e1c4af4c2967ad382131ecc9c
Author: Matthieu Jolimaitre <matthieu@imagevo.fr>
Date:   Tue Apr 9 02:05:02 2024 +0200

    init

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..688e137
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/deno.lock
diff --git a/.vscode/settings.json b/.vscode/settings.json
new file mode 100644
index 0000000..cbac569
--- /dev/null
+++ b/.vscode/settings.json
@@ -0,0 +1,3 @@
+{
+  "deno.enable": true
+}
diff --git a/client/main.ts b/client/main.ts
new file mode 100755
index 0000000..362af52
--- /dev/null
+++ b/client/main.ts
@@ -0,0 +1,125 @@
+#!/bin/env -S deno run --allow-net --allow-run
+import { MsgToClient, MsgToServer, mtc } from "../common/mod.ts";
+import { run } from "../common/utils.ts";
+import {
+	channel,
+	launch_caught,
+	log_from,
+	parsed_stream,
+	Receiver,
+	Sender,
+	serialized_stream,
+	wait,
+} from "../common/utils.ts";
+const log = log_from(import.meta);
+
+async function main() {
+	log("Client starting.");
+	const interface_ = await ServerInterface.connect(9999);
+	new InputHandler(interface_.outputs).spin();
+	const display = new DisplayHandler(interface_.outputs);
+	display.spin();
+	new MsgHandler(interface_.inputs, display).spin();
+	log("Connected.");
+
+	interface_.outputs.send({ kind: "ping", content: { message: "Machin." } });
+	log("Sent ping.");
+}
+
+class MsgHandler {
+	receiver;
+	display;
+
+	constructor(receiver: Receiver<MsgToClient>, display: DisplayHandler) {
+		this.receiver = receiver;
+		this.display = display;
+	}
+
+	async spin() {
+		for await (const event of this.receiver.iter()) {
+			if (event.kind === "ping_response") log("Received ping response :", event.content);
+			if (event.kind === "display") this.display.refresh(event.content.raw);
+		}
+	}
+}
+
+class InputHandler {
+	outputs;
+
+	constructor(outputs: Sender<MsgToServer>) {
+		this.outputs = outputs;
+	}
+
+	async read_one_char() {
+		const args = ["-i0", "sh", "-c", "read -n 1 OUT; echo -n $OUT"];
+		const command = new Deno.Command("stdbuf", { args, stdin: "inherit", stdout: "piped" });
+		const output = await command.output();
+		const result = new TextDecoder().decode(output.stdout);
+		console.log(`${String.fromCharCode(0x08)} `);
+		return result[0];
+	}
+
+	async spin() {
+		while (true) {
+			const read = await this.read_one_char();
+			if (read === "z") this.outputs.send({ kind: "input", content: { control: "up" } });
+			if (read === "s") this.outputs.send({ kind: "input", content: { control: "down" } });
+			if (read === "q") this.outputs.send({ kind: "input", content: { control: "left" } });
+			if (read === "d") this.outputs.send({ kind: "input", content: { control: "right" } });
+		}
+	}
+}
+
+class DisplayHandler {
+	outputs;
+
+	constructor(outputs: Sender<MsgToServer>) {
+		this.outputs = outputs;
+	}
+
+	async spin() {
+		while (true) {
+			await wait(100);
+			const [width, height] = await this.get_res();
+			this.outputs.send({ kind: "request_display", content: { width, height } });
+		}
+	}
+
+	async get_res() {
+		const width = parseInt(await run("tput", "cols")) / 2 - 2; // note : tiles are 2 char wide
+		const height = parseInt(await run("tput", "lines")) - 2;
+		return [width, height];
+	}
+
+	refresh(raw: string) {
+		const clear_sequence = String.fromCharCode(0o033) + String.fromCharCode(0o143);
+		console.log(clear_sequence + raw);
+	}
+}
+
+class ServerInterface {
+	inputs;
+	outputs;
+
+	constructor(inputs: Receiver<MsgToClient>, outputs: Sender<MsgToServer>) {
+		this.inputs = inputs;
+		this.outputs = outputs;
+	}
+
+	static async connect(port: number) {
+		const connection = await Deno.connect({ port });
+		return await ServerInterface.init(connection);
+	}
+
+	// deno-lint-ignore require-await
+	static async init(connection: Deno.Conn) {
+		// TODO : handshake ?
+		const [input_sender, input_receiver] = channel<MsgToClient>();
+		const [output_sender, output_receiver] = channel<MsgToServer>();
+		launch_caught(() => input_sender.send_all(parsed_stream(mtc.message_to_client_parser())(connection.readable)));
+		launch_caught(() => serialized_stream(output_receiver.iter())(connection.writable));
+		return new ServerInterface(input_receiver, output_sender);
+	}
+}
+
+if (import.meta.main) await main();
diff --git a/client/watch.sh b/client/watch.sh
new file mode 100755
index 0000000..65b3ae5
--- /dev/null
+++ b/client/watch.sh
@@ -0,0 +1,10 @@
+#!/bin/sh
+set -e
+cd "$(dirname "$(realpath "$0")")"
+
+nodemon -w ../common -w . -e ts -x '
+while true;
+do
+    ./main.ts;
+    sleep 1s;
+done'
diff --git a/common/message/message.ts b/common/message/message.ts
new file mode 100644
index 0000000..e69de29
diff --git a/common/message/to_client.ts b/common/message/to_client.ts
new file mode 100644
index 0000000..46081c8
--- /dev/null
+++ b/common/message/to_client.ts
@@ -0,0 +1,32 @@
+import { z } from "https://deno.land/x/zod@v3.22.4/mod.ts";
+import { ParserOutput } from "../utils.ts";
+
+export type MsgToClient = ParserOutput<typeof message_to_client_parser>;
+export function message_to_client_parser() {
+	return ping_response_parser()
+		.or(display_parser());
+}
+
+export type MsgPingResponse = ParserOutput<typeof ping_response_parser>;
+export function ping_response_parser() {
+	return z.object({
+		kind: z.literal("ping_response"),
+		content: z.object({
+			message: z.string(),
+		}),
+	});
+}
+
+export type MsgDisplay = ParserOutput<typeof display_parser>;
+export function display_parser() {
+	return z.object({
+		kind: z.literal("display"),
+		content: z.object({
+			raw: z.string(),
+		}),
+	});
+}
+
+function char_parser() {
+	return z.string().length(1);
+}
diff --git a/common/message/to_server.ts b/common/message/to_server.ts
new file mode 100644
index 0000000..d09e52b
--- /dev/null
+++ b/common/message/to_server.ts
@@ -0,0 +1,58 @@
+import { z } from "https://deno.land/x/zod@v3.22.4/mod.ts";
+import { ParserOutput } from "../utils.ts";
+
+export type MsgToServer = ParserOutput<typeof message_to_server_parser>;
+export function message_to_server_parser() {
+	return ping_parser()
+		.or(request_display_parser())
+		.or(input_parser())
+		.or(exit_parser());
+}
+
+export type MsgPing = ParserOutput<typeof ping_parser>;
+export function ping_parser() {
+	return z.object({
+		kind: z.literal("ping"),
+		content: z.object({
+			message: z.string(),
+		}),
+	});
+}
+
+export type MsgReqDisplay = ParserOutput<typeof request_display_parser>;
+export function request_display_parser() {
+	return z.object({
+		kind: z.literal("request_display"),
+		content: z.object({
+			width: z.number(),
+			height: z.number(),
+		}),
+	});
+}
+
+export type MsgInput = ParserOutput<typeof input_parser>;
+export function input_parser() {
+	return z.object({
+		kind: z.literal("input"),
+		content: z.object({
+			control: control_parser(),
+		}),
+	});
+}
+
+export type ClientInput = ParserOutput<typeof control_parser>;
+function control_parser() {
+	return z.literal("up")
+		.or(z.literal("down"))
+		.or(z.literal("left"))
+		.or(z.literal("right"))
+		.or(z.literal("interact"))
+		.or(z.literal("attack"));
+}
+
+export type MsgExit = ParserOutput<typeof exit_parser>;
+export function exit_parser() {
+	return z.object({
+		kind: z.literal("exit"),
+	});
+}
diff --git a/common/mod.ts b/common/mod.ts
new file mode 100644
index 0000000..c7dcae7
--- /dev/null
+++ b/common/mod.ts
@@ -0,0 +1,4 @@
+export * as mtc from "./message/to_client.ts";
+export * as mts from "./message/to_server.ts";
+export type { MsgToClient } from "./message/to_client.ts";
+export type { MsgToServer } from "./message/to_server.ts";
diff --git a/common/utils.ts b/common/utils.ts
new file mode 100644
index 0000000..159d4e8
--- /dev/null
+++ b/common/utils.ts
@@ -0,0 +1,322 @@
+import { assert, assertEquals, assertInstanceOf } from "https://deno.land/std@0.221.0/assert/mod.ts";
+import * as path from "https://deno.land/std@0.221.0/path/mod.ts";
+import { TextLineStream } from "https://deno.land/std@0.221.0/streams/mod.ts";
+import { z, ZodType } from "https://deno.land/x/zod@v3.22.4/mod.ts";
+
+export function parsed_stream<T>(parser: ZodType<T>) {
+	return async function* (readable: ReadableStream<Uint8Array>) {
+		const line_stream = readable
+			.pipeThrough(new TextDecoderStream())
+			.pipeThrough(new TextLineStream());
+		for await (const line of line_stream) yield parser.parse(JSON.parse(line));
+	};
+}
+
+export function serialized_stream<T>(generator: AsyncIterable<T>) {
+	return async function (writable: WritableStream<Uint8Array>) {
+		const stream = new TextEncoderStream();
+		stream.readable.pipeTo(writable);
+		for await (const item of generator) {
+			const writer = stream.writable.getWriter();
+			await writer.write(JSON.stringify(item) + "\n");
+			writer.releaseLock();
+		}
+	};
+}
+
+export type Consumer<T> = (item: T) => void;
+
+// deno-lint-ignore no-explicit-any
+export type ParserOutput<T extends () => ZodType<any, any, any>> = z.infer<ReturnType<T>>;
+
+export type PromiseSplit<T> = ReturnType<typeof split_promise<T>>;
+export function split_promise<T>() {
+	let resolver_ = null as Consumer<T> | null;
+	const promise = new Promise<T>((r) => {
+		resolver_ = r;
+	});
+	assert(resolver_ !== null);
+	const resolver = resolver_ as Consumer<T>;
+	return { promise, resolver };
+}
+
+export class AsyncQueue<T> {
+	private items;
+	private awaiting;
+
+	public constructor() {
+		this.items = [] as T[];
+		this.awaiting = [] as Consumer<void>[];
+	}
+
+	public push(item: T) {
+		this.items.push(item);
+		const [first] = this.awaiting.splice(0, 1);
+		if (first !== undefined) first();
+	}
+
+	public async pull() {
+		let first = this.take_first_item();
+		if (first !== undefined) return first;
+		const { promise, resolver } = split_promise<void>();
+		this.awaiting.push(resolver);
+		await promise;
+		first = this.take_first_item();
+		assert(first !== undefined);
+		return first as T;
+	}
+
+	private take_first_item() {
+		const [first] = this.items.splice(0, 1);
+		return first as T | undefined;
+	}
+}
+
+export function channel<T>() {
+	const queue = new AsyncQueue<T>();
+	return [new Sender(queue), new Receiver(queue)] as const;
+}
+
+export function channel_generator<T>(generator: AsyncIterable<T>) {
+	const [sender, receiver] = channel();
+	(async () => {
+		for await (const item of generator) sender.send(item);
+	})();
+	return receiver;
+}
+
+export class Sender<T> {
+	queue;
+
+	public constructor(queue: AsyncQueue<T>) {
+		this.queue = queue;
+	}
+
+	public send(item: T) {
+		this.queue.push(item);
+	}
+
+	public async send_all(iter: AsyncGenerator<T>) {
+		for await (const item of iter) this.send(item);
+	}
+}
+
+export class Receiver<T> {
+	queue;
+
+	public constructor(queue: AsyncQueue<T>) {
+		this.queue = queue;
+	}
+
+	public async receive() {
+		return await this.queue.pull();
+	}
+
+	public async *iter() {
+		while (true) yield this.receive();
+	}
+}
+
+export function range(from: number, to: number) {
+	return new Range(from, to);
+}
+
+export class Range {
+	from;
+	to;
+
+	constructor(from: number, to: number) {
+		this.from = from;
+		this.to = to;
+	}
+
+	includes(n: number) {
+		return (n >= this.from) && (n < this.to);
+	}
+
+	[Symbol.iterator]() {
+		let index = this.from;
+		const to = this.to;
+		return (function* () {
+			while (index < to) yield index++;
+		})();
+	}
+}
+
+export async function launch_caught<T>(
+	operation: () => Promise<T> | T,
+	handler: null | ((error: unknown) => void) = null,
+) {
+	try {
+		return await operation();
+	} catch (error) {
+		if (handler !== null) handler(error);
+		else console.error("Lanched Uncaught :", error);
+	}
+}
+
+export function log_from(meta: ImportMeta) {
+	return function (...args: unknown[]) {
+		const mod = path.basename(new URL(meta.url).pathname);
+		console.log(`[${mod}]`, ...args);
+	};
+}
+
+export class Vec2 {
+	private x_;
+	private y_;
+
+	public constructor(x: number, y: number) {
+		this.x_ = Math.round(x);
+		this.y_ = Math.round(y);
+	}
+
+	public x() {
+		return this.x_;
+	}
+
+	public y() {
+		return this.y_;
+	}
+
+	public scale(factor: number) {
+		return new Vec2(this.x_ * factor, this.y_ * factor);
+	}
+
+	public neg() {
+		return this.scale(-1);
+	}
+
+	public add(other: Vec2) {
+		return new Vec2(this.x_ + other.x_, this.y_ + other.y_);
+	}
+
+	public sub(other: Vec2) {
+		return this.add(other.neg());
+	}
+
+	public inside(corner_tl: Vec2, corner_br: Vec2) {
+		if (!range(corner_tl.x(), corner_br.x()).includes(this.x())) return false;
+		if (!range(corner_tl.y(), corner_br.y()).includes(this.y())) return false;
+		return true;
+	}
+
+	public eq(other: Vec2) {
+		return (this.x() === other.x()) && (this.y() === other.y());
+	}
+
+	public neq(other: Vec2) {
+		return !this.eq(other);
+	}
+
+	public len() {
+		return Math.sqrt(this.x() ** 2 + this.y() ** 2);
+	}
+
+	public distance(other: Vec2) {
+		return this.sub(other).len();
+	}
+
+	public overlaps(other: Vec2) {
+		return this.distance(other) < 1;
+	}
+}
+
+export function v2(x: number, y: number) {
+	return new Vec2(x, y);
+}
+
+export function* enumerate<T>(iterator: Iterable<T>) {
+	let index = 0;
+	for (const item of iterator) yield [index++, item] as [number, T];
+}
+
+export function* chunks<T>(iterator: Iterable<T>, size: number) {
+	let current = [];
+	for (const item of iterator) {
+		current.push(item);
+		if (current.length < size) continue;
+		yield current;
+		current = [];
+	}
+}
+
+Deno.test("test_chunk", () => {
+	assertEquals(
+		[...chunks([1, 2, 3, 4, 5, 6, 7], 3)],
+		[[1, 2, 3], [4, 5, 6]],
+	);
+});
+
+export function wait(ms: number) {
+	return new Promise((res) => setTimeout(res, ms));
+}
+
+export async function run(cmd: string, ...args: string[]) {
+	const command = new Deno.Command(cmd, { args, stdout: "piped" });
+	const output = await command.output();
+	if (!output.success) throw new Error();
+	return new TextDecoder().decode(output.stdout);
+}
+
+export type Prototyped<P = unknown> = { constructor: { prototype: P } };
+export type Constructible<I = unknown> = new (...args: unknown[]) => I;
+export class ClassMap<B = unknown> {
+	private inner;
+
+	constructor() {
+		this.inner = new Map();
+	}
+
+	insert<V extends Prototyped & B>(object: V) {
+		const prototype = object.constructor.prototype;
+		if (this.inner.has(prototype)) throw new Error();
+		this.inner.set(prototype, object);
+	}
+
+	get<I extends B, C extends Constructible<I>>(class_: C) {
+		const value = this.inner.get(class_.prototype);
+		if (value === undefined) return null;
+		assertInstanceOf(value, class_);
+		return value;
+	}
+}
+
+Deno.test("test_classmap", () => {
+	{
+		class Truc {}
+		class Machin {}
+		class Chose {}
+
+		const map = new ClassMap();
+		const truc = new Truc();
+		map.insert(truc);
+		const machin = new Machin();
+		map.insert(machin);
+
+		assert(map.get(Truc) === truc);
+		assert(map.get(Machin) !== truc);
+		assert(map.get(Machin) === machin);
+		assert(map.get(Chose) === null);
+	}
+	{
+		interface Machinable {
+			machin(): number;
+		}
+		// deno-lint-ignore no-unused-vars
+		class Truc {}
+		class Machin implements Machinable {
+			machin = () => 35;
+		}
+		const map = new ClassMap<Machinable>();
+		map.insert(new Machin());
+		// map.insert(new Truc()); // note : Fails with improper typing.
+
+		map.get(Machin);
+		// map.get(Truc); // note : Fails with improper typing.
+	}
+});
+
+export function maybe<T>(item: T) {
+	return item as T | undefined;
+}
diff --git a/data/structures/houses.txt b/data/structures/houses.txt
new file mode 100644
index 0000000..29306e1
--- /dev/null
+++ b/data/structures/houses.txt
@@ -0,0 +1,8 @@
+[][][]  [][]
+[]        []
+[]        []
+[]        [][][]
+[][][][][][]  []
+      []
+      []      []
+      [][][][][]
diff --git a/deno.json b/deno.json
new file mode 100644
index 0000000..92b61b1
--- /dev/null
+++ b/deno.json
@@ -0,0 +1,6 @@
+{
+	"fmt": {
+		"useTabs": true,
+		"lineWidth": 120
+	}
+}
diff --git a/server/engine.ts b/server/engine.ts
new file mode 100644
index 0000000..bf13550
--- /dev/null
+++ b/server/engine.ts
@@ -0,0 +1,153 @@
+import { assertEquals } from "https://deno.land/std@0.221.0/assert/mod.ts";
+import { chunks, enumerate, log_from, Prototyped, range, Vec2 } from "../common/utils.ts";
+import { ClientInterface } from "./network.ts";
+import { Session } from "./entities/player.ts";
+import { ClassMap } from "../common/utils.ts";
+import { maybe } from "../common/utils.ts";
+const log = log_from(import.meta);
+
+export class WorldEntity {
+	display;
+	world;
+	identifier;
+	position;
+	compontents;
+
+	constructor(world: World, identifier: number, display: string, position: Vec2, ...components: Prototyped[]) {
+		this.display = display;
+		this.world = world;
+		this.identifier = identifier;
+		this.position = position;
+		this.compontents = new ClassMap();
+		for (const c of components) this.compontents.insert(c);
+	}
+}
+
+export class World {
+	next_id;
+	entities;
+
+	constructor() {
+		this.next_id = 0;
+		this.entities = new Map<number, WorldEntity>();
+	}
+
+	spawn_entity(display: string, pos: Vec2) {
+		const entity = new WorldEntity(this, this.next_id++, display, pos);
+		this.entities.set(entity.identifier, entity);
+		return entity;
+	}
+
+	async spawn_structure(file_path: string, origin: Vec2) {
+		const content = await Deno.readTextFile(file_path);
+		let count = 0;
+		for (const [y, line] of enumerate(content.split("\n"))) {
+			for (const [x, chars] of enumerate(chunks(line, 2))) {
+				const display = chars[0] + chars[1];
+				if (display === "  ") continue;
+				this.spawn_entity(display, origin.add(new Vec2(x, y)));
+				count += 1;
+			}
+		}
+		log("Spawned", count, "tiles from", file_path);
+	}
+
+	render(center: Vec2, size: Vec2) {
+		const radius = size.scale(0.5);
+		const result = Array.from(range(0, size.y())).map(() => Array.from(range(0, size.x())).map(() => "  "));
+		const top_left = center.sub(radius);
+		const bottom_right = center.add(radius);
+		for (const entity of this.entities.values()) {
+			if (!entity.position.inside(top_left, bottom_right)) continue;
+			const local_pos = entity.position.sub(top_left);
+			result[local_pos.y()][local_pos.x()] = entity.display;
+		}
+		return result.map((line) => line.join("")).toReversed().join("\n");
+	}
+
+	move_collide(entity_id: number, displacement: Vec2) {
+		let result = false;
+		const entity = this.get_entity(entity_id);
+		if (entity === undefined) return result;
+		for (const step of displacement_steps(entity.position, displacement)) {
+			const collision = this.get_entity_at(step);
+			if (collision !== undefined) return result;
+			entity.position = step;
+			result = true;
+		}
+		return result;
+	}
+
+	get_entity(entity_id: number) {
+		return this.entities.get(entity_id);
+	}
+
+	*get_entities_at(pos: Vec2) {
+		for (const entity of this.entities.values()) if (entity.position.overlaps(pos)) yield entity;
+	}
+
+	get_entity_at(pos: Vec2) {
+		return maybe([...this.get_entities_at(pos)][0]);
+	}
+
+	*get_entities_in_range(min: Vec2, max: Vec2) {
+		for (const entity of this.entities.values()) if (entity.position.inside(min, max)) yield entity;
+	}
+
+	get_entity_in_range(min: Vec2, max: Vec2) {
+		return maybe([...this.get_entities_in_range(min, max)][0]);
+	}
+
+	kill(entity_id: number) {
+		this.entities.delete(entity_id);
+	}
+}
+
+export class Engine {
+	world;
+
+	constructor(world: World) {
+		this.world = world;
+	}
+
+	async start() {
+		log("Started engine.");
+	}
+
+	add_session(client: ClientInterface) {
+		const player_entity = this.world.spawn_entity("`/", new Vec2(0, 0));
+		const session = new Session(client, this.world, player_entity);
+		session.spin();
+	}
+}
+
+function* displacement_steps(position: Vec2, displacement: Vec2) {
+	let pos = position;
+	let left = displacement;
+	while (left.len() >= 1) {
+		if (left.x() >= 1) {
+			pos = pos.add(new Vec2(1, 0));
+			left = left.sub(new Vec2(1, 0));
+		}
+		if (left.x() <= -1) {
+			pos = pos.add(new Vec2(-1, 0));
+			left = left.sub(new Vec2(-1, 0));
+		}
+		if (left.y() >= 1) {
+			pos = pos.add(new Vec2(0, 1));
+			left = left.sub(new Vec2(0, 1));
+		}
+		if (left.y() <= -1) {
+			pos = pos.add(new Vec2(0, -1));
+			left = left.sub(new Vec2(0, -1));
+		}
+		yield pos;
+	}
+}
+
+Deno.test("test_displacement", () => {
+	assertEquals(
+		[...displacement_steps(new Vec2(1, 1), new Vec2(4, 6))],
+		[new Vec2(2, 2), new Vec2(3, 3), new Vec2(4, 4), new Vec2(5, 5), new Vec2(5, 6), new Vec2(5, 7)],
+	);
+});
diff --git a/server/entities/enemy.ts b/server/entities/enemy.ts
new file mode 100644
index 0000000..cd7b461
--- /dev/null
+++ b/server/entities/enemy.ts
@@ -0,0 +1,33 @@
+import { World, WorldEntity } from "../engine.ts";
+import { v2, Vec2 } from "../../common/utils.ts";
+import { wait } from "../../common/utils.ts";
+
+export class Enemy {
+	entity;
+	alive;
+
+	constructor(entity: WorldEntity) {
+		this.entity = entity;
+		this.alive = true;
+	}
+
+	static spawn(world: World, pos: Vec2) {
+		const entity = world.spawn_entity("èé", pos);
+	}
+
+	async spin() {
+		while (this.alive) {
+			await wait(500);
+			const target = this.find_target();
+		}
+	}
+
+	find_target() {
+		const world = this.entity.world;
+		const local_origin = this.entity.position;
+		const found = world.get_entities_in_range(local_origin.sub(v2(3, 3)), local_origin.add(v2(3, 3)));
+		for (const entity of found) {
+			// if (entity.compontents.get())
+		}
+	}
+}
diff --git a/server/entities/player.ts b/server/entities/player.ts
new file mode 100644
index 0000000..cd9b66b
--- /dev/null
+++ b/server/entities/player.ts
@@ -0,0 +1,61 @@
+import { mts } from "../../common/mod.ts";
+import { log_from, Vec2 } from "../../common/utils.ts";
+import { World, WorldEntity } from "../engine.ts";
+import { ClientInterface } from "../network.ts";
+const log = log_from(import.meta);
+
+export class Session {
+	client;
+	world;
+	player_entity;
+
+	constructor(client: ClientInterface, world: World, player_entity: WorldEntity) {
+		this.client = client;
+		this.world = world;
+		this.player_entity = player_entity;
+	}
+
+	async spin() {
+		try {
+			for await (const input of this.client.inputs.iter()) {
+				if (input.kind !== "request_display") log("Received", input);
+
+				if (input.kind === "ping") this.client.outputs.send({ kind: "ping_response", content: input.content });
+				if (input.kind === "request_display") this.send_display(input.content.width, input.content.height);
+				if (input.kind === "input") this.handle_input(input);
+				if (input.kind === "exit") this.world.kill(this.player_entity.identifier);
+			}
+		} catch (error) {
+			console.error("Session loop failed, ", error);
+			this.world.kill(this.player_entity.identifier);
+		}
+	}
+
+	send_display(width: number, height: number) {
+		const raw = this.world.render(this.player_entity.position, new Vec2(width, height));
+		this.client.outputs.send({ kind: "display", content: { raw } });
+	}
+
+	handle_input(input: mts.MsgInput) {
+		if (input.content.control === "up") this.world.move_collide(this.player_entity.identifier, new Vec2(0, 1));
+		if (input.content.control === "down") this.world.move_collide(this.player_entity.identifier, new Vec2(0, -1));
+		if (input.content.control === "left") this.world.move_collide(this.player_entity.identifier, new Vec2(-1, 0));
+		if (input.content.control === "right") this.world.move_collide(this.player_entity.identifier, new Vec2(1, 0));
+	}
+}
+
+export class PlayerComponent {
+	entity;
+
+	constructor(entity: WorldEntity) {
+		this.entity = entity;
+	}
+
+	move(direction: Vec2) {
+		return this.entity.world.move_collide(this.entity.identifier, direction);
+	}
+
+	render(res: Vec2) {
+		return this.entity.world.render(this.entity.position, res);
+	}
+}
diff --git a/server/main.ts b/server/main.ts
new file mode 100755
index 0000000..500c20c
--- /dev/null
+++ b/server/main.ts
@@ -0,0 +1,24 @@
+#!/bin/env -S deno run --allow-net --allow-read
+
+import { log_from, Vec2 } from "../common/utils.ts";
+import { Engine, World } from "./engine.ts";
+import { Enemy } from "./entities/enemy.ts";
+import { Gateway } from "./network.ts";
+const log = log_from(import.meta);
+
+async function main() {
+	log("Starting.");
+	const world = new World();
+	await world.spawn_structure("../data/structures/houses.txt", new Vec2(2, 2));
+	const engine = new Engine(world);
+	engine.start();
+
+	Enemy.spawn(world, new Vec2(-3, -3));
+
+	const port = 9999;
+	const gateway = new Gateway(port);
+	log("Awaiting connection.");
+	for await (const session of gateway.accept()) engine.add_session(session);
+}
+
+if (import.meta.main) await main();
diff --git a/server/network.ts b/server/network.ts
new file mode 100644
index 0000000..719eb3a
--- /dev/null
+++ b/server/network.ts
@@ -0,0 +1,50 @@
+#!/bin/env -S deno run --allow-net
+
+import { MsgToClient, MsgToServer, mts } from "../common/mod.ts";
+import {
+	channel,
+	launch_caught,
+	log_from,
+	parsed_stream,
+	Receiver,
+	Sender,
+	serialized_stream,
+} from "../common/utils.ts";
+const log = log_from(import.meta);
+
+export class Gateway {
+	server;
+	constructor(port: number) {
+		this.server = Deno.listen({ port });
+		log("Listening on", port);
+	}
+	async *accept() {
+		for await (const connection of this.server) {
+			const session = await ClientInterface.init(connection);
+			log("New session.");
+			yield session;
+		}
+	}
+}
+
+export class ClientInterface {
+	inputs;
+	outputs;
+
+	constructor(inputs: Receiver<MsgToServer>, outputs: Sender<MsgToClient>) {
+		this.inputs = inputs;
+		this.outputs = outputs;
+	}
+
+	// deno-lint-ignore require-await
+	static async init(connection: Deno.Conn) {
+		// TODO : handshake ?
+		const [input_sender, input_receiver] = channel<MsgToServer>();
+		const [output_sender, output_receiver] = channel<MsgToClient>();
+		input_sender.send_all(parsed_stream(mts.message_to_server_parser())(connection.readable))
+			.finally(() => input_sender.send({ kind: "exit" }));
+		serialized_stream(output_receiver.iter())(connection.writable)
+			.finally(() => input_sender.send({ kind: "exit" }));
+		return new ClientInterface(input_receiver, output_sender);
+	}
+}
diff --git a/server/watch.sh b/server/watch.sh
new file mode 100755
index 0000000..350b253
--- /dev/null
+++ b/server/watch.sh
@@ -0,0 +1,5 @@
+#!/bin/sh
+set -e
+cd "$(dirname "$(realpath "$0")")"
+
+nodemon -w ../common -w . -e ts -x 'clear && ./main.ts'