/**
 * oracle — the door. The security floor, the body caps and the table of
 * paths live here; the mind is in `oracle.ts`, the ledger in `db.ts` and
 * every page in `pages.ts`.
 *
 * The ledger is a SQLite file under FORGE_APP_DATA. Production and each
 * preview get their own directory, so a preview starts with a copy of
 * production's verdicts and never writes back to them.
 */

import { join } from "node:path";
import * as ledger from "./db.ts";
import { isOutcome } from "./oracle.ts";
import { homePage, ledgerPage, notFoundPage, verdictPage } from "./pages.ts";

const db = ledger.open();

const chrome = {
  env: process.env.FORGE_APP_ENV ?? "local",
  pull: process.env.FORGE_APP_PULL,
  commit: (process.env.FORGE_APP_COMMIT ?? "").slice(0, 7),
  ssh: process.env.FORGE_APP_SSH,
};

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

// 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.
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;
};

// 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();
}

export const server = Bun.serve({
  port: Number(process.env.PORT ?? 8080),
  hostname: process.env.HOST ?? "127.0.0.1",
  async fetch(request) {
    const url = new URL(request.url);
    if (request.method === "POST" && !sameOrigin(request))
      return new Response("forbidden", { status: 403 });

    // Ask. An empty question is not a question; the same question is not a
    // new one, which `ledger.ask` enforces in one statement.
    if (request.method === "POST" && url.pathname === "/ask") {
      const form = await readForm(request);
      if (form === undefined)
        return new Response("too large", { status: 413, headers: SECURITY });
      const question = String(form.get("question") ?? "").trim();
      if (question === "") return Response.redirect("/", 303);
      const row = ledger.ask(db, question);
      return Response.redirect(`/v/${row.id}`, 303);
    }

    // Score a verdict. Only the three words count; anything else is a
    // client inventing states for the ledger to hold.
    const judging = url.pathname.match(/^\/v\/(\d{1,15})\/judge$/);
    if (request.method === "POST" && judging) {
      const form = await readForm(request);
      if (form === undefined)
        return new Response("too large", { status: 413, headers: SECURITY });
      const outcome = String(form.get("outcome") ?? "");
      const id = Number(judging[1]);
      if (!isOutcome(outcome) || ledger.get(db, id) === null)
        return html(notFoundPage(chrome), 404);
      ledger.judge(db, id, outcome);
      return Response.redirect(`/v/${id}`, 303);
    }

    const reading = request.method === "GET" || request.method === "HEAD";

    if (reading && url.pathname === "/") {
      const full = html(homePage(chrome, ledger.recent(db), ledger.scored(db)));
      return request.method === "HEAD"
        ? new Response(null, { status: full.status, headers: full.headers })
        : full;
    }

    const permalink = url.pathname.match(/^\/v\/(\d{1,15})$/);
    if (reading && permalink) {
      const row = ledger.get(db, Number(permalink[1]));
      return row === null
        ? html(notFoundPage(chrome), 404)
        : html(verdictPage(chrome, row));
    }

    if (reading && url.pathname === "/ledger") {
      const show = url.searchParams.get("show") ?? "all";
      const filter = ledger.isFilter(show) ? show : "all";
      return html(ledgerPage(chrome, ledger.ledger(db, filter), filter));
    }

    // Files under ./static are served as they are, cached for a year: name
    // them by content (app.3f2a9c.js) and a change is a new name, never a
    // stale cache. The path is confined to the directory.
    if (reading && 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 html(notFoundPage(chrome), 404);
  },
  // 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);
  },
});

console.log(
  `the oracle is listening on http://${server.hostname}:${server.port} (${chrome.env})`,
);