fable/val Public Public: anyone can read this; nobody can change it.

/**

 * val — the door. Routing, sessions, sockets and the security floor; the

 * game itself is in src/match.ts and the live one in src/arena.ts.

 *

 * A seat belongs to a session cookie, so the same browser gets the same

 * player back across a reload, and a socket is only ever given a seat the

 * server chose.

 */

import { createHash, randomUUID } from "node:crypto";

import { join } from "node:path";

import { AGENTS, SLOTS } from "./abilities.ts";

import { attach, command, findPlayer, match, release, snapshot, startArena, takeSeat, type Command } from "./arena.ts";

import { recentResults } from "./db.ts";

import { gridRows, TILE } from "./map.ts";

import { gamePage } from "./pages/game.ts";

const env = process.env.FORGE_APP_ENV ?? "local";

const pull = process.env.FORGE_APP_PULL;

const commit = (process.env.FORGE_APP_COMMIT ?? "").slice(0, 7);

const where = env === "preview" ? `preview of pull #${pull ?? "?"}` : env;

// The security floor every response stands on. Scripts and styles come from

// this origin (inline styles allowed, inline scripts not), nothing frames us,

// browsers never guess a content type, and referrers stay on this site.

// The app's public address is what the forge told us, never the socket's.

const publicOrigin = new URL(process.env.FORGE_APP_URL ?? "http://localhost").origin;

const SECURITY = {

  "content-security-policy":

    "default-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'none'; base-uri 'none'; form-action 'self'",

  "x-content-type-options": "nosniff",

  "referrer-policy": "strict-origin-when-cross-origin",

  "permissions-policy": "camera=(), microphone=(), geolocation=()",

  // Once served over https, always: browsers remember for a year.

  ...(publicOrigin.startsWith("https:")

    ? { "strict-transport-security": "max-age=31536000" }

    : {}),

};

const html = (body: string, status = 200, extra: Record<string, string> = {}): Response =>

  new Response(body, { status, headers: { "content-type": "text/html; charset=utf-8", ...SECURITY, ...extra } });

// A browser on another site can make a person's browser POST here; it cannot

// make that request look same-origin. Browsers say where a request came from

// (Sec-Fetch-Site, or Origin); a request that names another site is refused.

// The address the forge published is the one that counts, but a browser

// reaching the app by another name (localhost, an IP, a tunnel) sends that

// host in both the URL and the Origin — a cross-site request never can.

const sameOrigin = (request: Request): boolean => {

  const site = request.headers.get("sec-fetch-site");

  if (site !== null) return site === "same-origin" || site === "none";

  const origin = request.headers.get("origin");

  return origin === null || origin === publicOrigin || origin === new URL(request.url).origin;

};

// A request body is read up to a cap and no further, counting the bytes as

// they arrive. A declared Content-Length is a claim: a chunked request has

// none, and a lie is free. Undefined means "too large" — refuse it. Past the

// cap the rest is drained and dropped so the connection stays usable for

// the next request; past eight times the cap it is cut off instead.

const BODY_MAX = 64 * 1024;

async function readBody(request: Request, max = BODY_MAX): Promise<Uint8Array | undefined> {

  const reader = request.body?.getReader();

  if (reader === undefined) return new Uint8Array();

  const parts: Uint8Array[] = [];

  let size = 0;

  for (;;) {

    const { done, value } = await reader.read();

    if (done) break;

    size += value.byteLength;

    if (size > max) {

      for (;;) {

        const next = await reader.read();

        if (next.done) return undefined;

        size += next.value.byteLength;

        if (size > max * 8) {

          await reader.cancel();

          return undefined;

        }

      }

    }

    parts.push(value);

  }

  const body = new Uint8Array(size);

  let at = 0;

  for (const part of parts) {

    body.set(part, at);

    at += part.byteLength;

  }

  return body;

}

// The form fields of a capped body, decoded the way the browser sent them

// (a plain form or a multipart one), by handing the bytes back to a Request.

async function readForm(request: Request): Promise<FormData | undefined> {

  const body = await readBody(request);

  if (body === undefined) return undefined;

  return new Request(request.url, {

    method: "POST",

    headers: { "content-type": request.headers.get("content-type") ?? "" },

    body,

  }).formData();

}

// ------------------------------------------------------------- the client

// The client is a handful of small modules under static/ — the renderer, the

// map, the crosshair, the ray maths — bundled into one file at start-up so a

// browser makes one request and the maths can still be imported by the tests.

// It is named by its content: a change is a new URL, so a year-long cache is

// never stale.

const built = await Bun.build({

  entrypoints: [join(import.meta.dir, "..", "static", "val.js")],

  target: "browser",

});

if (!built.success) throw new AggregateError(built.logs, "the client would not build");

const scriptBody = await built.outputs[0]!.text();

const scriptHash = createHash("sha256").update(scriptBody).digest("hex").slice(0, 10);

const scriptUrl = `/static/val.${scriptHash}.js`;

// ------------------------------------------------------------- sessions

const cookies = (request: Request): Record<string, string> => {

  const out: Record<string, string> = {};

  for (const part of (request.headers.get("cookie") ?? "").split(";")) {

    const at = part.indexOf("=");

    if (at < 1) continue;

    out[part.slice(0, at).trim()] = decodeURIComponent(part.slice(at + 1).trim());

  }

  return out;

};

const SESSION = "val_session";

const NAME = "val_name";

/** A name is one line of plain text, sixteen characters, nothing clever. */

const cleanName = (raw: unknown): string => {

  const text = String(raw ?? "")

    .replace(/[\u0000-\u001f\u007f<>"'\\]/g, "")

    .trim()

    .slice(0, 16);

  return text.length >= 1 ? text : "";

};

const setCookie = (name: string, value: string, httpOnly: boolean): string =>

  `${name}=${encodeURIComponent(value)}; Path=/; SameSite=Lax; Max-Age=604800${httpOnly ? "; HttpOnly" : ""}${publicOrigin.startsWith("https:") ? "; Secure" : ""}`;

type SocketData = { session: string; playerId: string };

// ---------------------------------------------------------------- routing

export const server = Bun.serve<SocketData, Record<string, never>>({

  port: Number(process.env.PORT ?? 8080),

  hostname: process.env.HOST ?? "127.0.0.1",

  async fetch(request, self) {

    const url = new URL(request.url);

    const jar = cookies(request);

    const session = jar[SESSION] ?? randomUUID();

    const fresh = jar[SESSION] === undefined;

    if (request.method === "POST" && !sameOrigin(request))

      return new Response("forbidden", { status: 403, headers: SECURITY });

    if (request.method === "POST" && url.pathname === "/join") {

      const form = await readForm(request);

      if (form === undefined) return new Response("too large", { status: 413, headers: SECURITY });

      const name = cleanName(form.get("name"));

      const headers = new Headers({ location: "/", ...SECURITY });

      headers.append("set-cookie", setCookie(SESSION, session, true));

      if (name) {

        headers.append("set-cookie", setCookie(NAME, name, false));

        takeSeat(session, name);

      }

      return new Response(null, { status: 303, headers });

    }

    // The socket: one seat per session, taken from a bot where it stands.

    if (url.pathname === "/ws") {

      if (!sameOrigin(request)) return new Response("forbidden", { status: 403, headers: SECURITY });

      const name = cleanName(jar[NAME]) || `Guest-${session.slice(0, 4)}`;

      const player = takeSeat(session, name);

      if (!player) return new Response("no seats", { status: 503, headers: SECURITY });

      const upgraded = self.upgrade(request, { data: { session, playerId: player.id } });

      return upgraded ? undefined : new Response("expected a websocket", { status: 426, headers: SECURITY });

    }

    if (url.pathname === "/" && (request.method === "GET" || request.method === "HEAD")) {

      const body = gamePage({

        state: match(),

        script: scriptUrl,

        name: cleanName(jar[NAME]),

        env: where,

        commit,

        ssh: process.env.FORGE_APP_SSH,

        results: recentResults(3),

      });

      const response = html(body, 200, fresh ? { "set-cookie": setCookie(SESSION, session, true) } : {});

      return request.method === "HEAD"

        ? new Response(null, { status: response.status, headers: response.headers })

        : response;

    }

    // The agents and their kits: what every ability does, its price and its

    // charges, so the buy panel can label itself. The same table the server

    // plays by, and no secret in it.

    if (url.pathname === "/agents.json" && (request.method === "GET" || request.method === "HEAD"))

      return Response.json(

        {

          agents: AGENTS.map((a) => ({

            id: a.id,

            name: a.name,

            role: a.role,

            blurb: a.blurb,

            abilities: Object.fromEntries(

              SLOTS.map((slot) => {

                const ability = a.abilities[slot];

                return [

                  slot,

                  {

                    name: ability.name,

                    cost: ability.cost,

                    charges: ability.charges,

                    cooldown: ability.cooldown,

                    points: ability.points,

                    text: ability.text,

                  },

                ];

              }),

            ),

          })),

        },

        { headers: { "cache-control": "public, max-age=300", ...SECURITY } },

      );

    // The map is the same for everybody and changes only when the code does.

    if (url.pathname === "/map.json" && (request.method === "GET" || request.method === "HEAD"))

      return Response.json(

        { rows: gridRows(), tile: TILE },

        { headers: { "cache-control": "public, max-age=300", ...SECURITY } },

      );

    if (url.pathname === scriptUrl)

      return new Response(scriptBody, {

        headers: {

          "content-type": "text/javascript; charset=utf-8",

          "cache-control": "public, max-age=31536000, immutable",

          ...SECURITY,

        },

      });

    // Files under ./static are served as they are, cached for a year: name

    // them by content and a change is a new name, never a stale cache. The

    // path is confined to the directory.

    if (url.pathname.startsWith("/static/") && !url.pathname.includes("..")) {

      const file = Bun.file(join(import.meta.dir, "..", url.pathname.slice(1)));

      if (await file.exists())

        return new Response(file, {

          headers: { "cache-control": "public, max-age=31536000, immutable", ...SECURITY },

        });

    }

    return new Response("not found", { status: 404, headers: SECURITY });

  },

  websocket: {

    maxPayloadLength: 4 * 1024,

    open(socket) {

      const { session, playerId } = socket.data;

      attach(session, playerId, (data) => socket.send(data));

      socket.send(snapshot(playerId));

    },

    message(socket, raw) {

      // Anything a client sends is a claim: it is parsed, bounded and given

      // to the arena, which decides what it is allowed to mean.

      if (typeof raw !== "string" || raw.length > 4096) return;

      let parsed: unknown;

      try {

        parsed = JSON.parse(raw);

      } catch {

        return;

      }

      if (typeof parsed !== "object" || parsed === null) return;

      command(socket.data.playerId, parsed as Command);

    },

    close(socket) {

      release(socket.data.session);

    },

  },

  // A bug answers with the floor and nothing else: never the runtime's own

  // error page, which carries source and paths, and never without the

  // headers. The detail goes to the log, where it belongs.

  error(error) {

    console.error(error);

    return html("<h1>Something went wrong</h1>", 500);

  },

});

startArena();

console.log(`val listening on http://${server.hostname}:${server.port} (${env})`);

export { findPlayer };