// Server F's front door (plan §8.2): one HTTP server — /healthz for the
// proxy, /__auth for the editor's frame (ticket in, cookie out), /svc/* for
// the dashboard (with the service key), /blobs for the large binary files
// of the projects' computers, the WebSockets /sync for the shared
// documents and /sim?project=… for the simulation rooms (the session's grant
// decides there as at /sync; a refusal closes the socket with its reason),
// and the editor's page and bundle (editorFiles.ts) for anything else; what
// is none of these is not found. A WebSocket from a page of another
// origin is refused (a page elsewhere under the same domain would bring the
// person's cookie along: SameSite only tells sites apart). Closed, it first
// takes no one new (a client lets go and comes back at once, which would
// keep its document open), stops every room (what it left written back),
// then lets everyone go, waits until every document is stored and unloaded,
// and stops. A /sim socket that answers no ping for PING_MILLISECONDS is
// let go (the proxy keeps an idle socket an hour; a tablet that went away
// says nothing).

import { createServer, type IncomingMessage, type Server, type ServerResponse } from 'node:http';
import type { AddressInfo, Socket } from 'node:net';
import { SIM_REFUSED_CODE, type SyncRefusal } from '@mdg-filius/protocol';
import { WebSocketServer, type WebSocket } from 'ws';
import { exchangeTicket } from './auth.js';
import { handleBlobs } from './blobRoutes.js';
import type { BlobStore } from './blobs.js';
import type { EditorFiles } from './editorFiles.js';
import { errorText, type Log } from './log.js';
import { handleService } from './service.js';
import { holdMessages, SimRooms } from './simRooms.js';
import { cookieValue, createSync, SESSION_COOKIE, type Sync, type SyncOptions } from './sync.js';
import { isUuid } from './ticket.js';

export const PING_MILLISECONDS = 30_000;
/** A message to a room at most. */
export const SIM_MESSAGE_BYTES = 1024 * 1024;

export interface FiliusServer {
  readonly port: number;
  readonly sync: Sync;
  readonly sims: SimRooms;
  close(): Promise<void>;
}

export interface ServerOptions extends SyncOptions {
  readonly port?: number;
  readonly host?: string;
  readonly log: Log;
  readonly ticketSecret: string;
  readonly serviceKey: string;
  /** The origins the editor is served from (FILIUS_ORIGINS): a WebSocket from another is refused. */
  readonly origins: readonly string[];
  readonly secureCookie: boolean;
  /** The bundled room thread (dist/simWorker.mjs). */
  readonly workerUrl: URL;
  readonly blobs: BlobStore;
  /** The editor's page and bundle; without them only F's own routes answer (development, tests). */
  readonly editor?: EditorFiles;
  readonly simThreads?: number;
  readonly lingerMilliseconds?: number;
  readonly pingMilliseconds?: number;
}

function refuse(socket: Socket, status: string): void {
  socket.end(`HTTP/1.1 ${status}\r\nConnection: close\r\n\r\n`);
}

function json(response: ServerResponse, status: number, value: object): void {
  response.writeHead(status, { 'content-type': 'application/json' });
  response.end(JSON.stringify(value));
}

export async function startServer(options: ServerOptions): Promise<FiliusServer> {
  const sync = createSync(options);
  const { hocuspocus } = sync;
  const sims = new SimRooms({
    hocuspocus,
    blobs: options.blobs,
    log: options.log,
    workerUrl: options.workerUrl,
    ...(options.simThreads === undefined ? {} : { threads: options.simThreads }),
    ...(options.lingerMilliseconds === undefined ? {} : { lingerMilliseconds: options.lingerMilliseconds }),
  });
  const sockets = new WebSocketServer({ noServer: true });
  const simSockets = new WebSocketServer({ noServer: true, maxPayload: SIM_MESSAGE_BYTES });
  const alive = new WeakSet<WebSocket>();
  const pings = setInterval(() => {
    for (const socket of simSockets.clients) {
      if (!alive.delete(socket)) socket.terminate();
      else socket.ping();
    }
  }, options.pingMilliseconds ?? PING_MILLISECONDS);
  let closing = false;
  const admit = async (socket: WebSocket, request: IncomingMessage) => {
    alive.add(socket);
    socket.on('pong', () => alive.add(socket));
    const held = holdMessages(socket);
    const refuse = (reason: SyncRefusal, user?: string) => {
      options.log.info('sim.refused', { reason, ...(user === undefined ? {} : { user }) });
      held.release();
      socket.close(SIM_REFUSED_CODE, reason);
    };
    const project = new URL(request.url ?? '/', 'http://filius').searchParams.get('project');
    if (!isUuid(project)) return refuse('notAProject');
    const key = cookieValue(request.headers.cookie, SESSION_COOKIE);
    const access = key === undefined ? ({ kind: 'notSignedIn' } as const) : await options.sessions.access(key, project);
    if (access.kind !== 'granted') return refuse(access.kind, access.kind === 'notSignedIn' ? undefined : access.person.login);
    try {
      await sims.join(socket, project, { user: access.person.user, login: access.person.login, name: access.person.name, write: access.level === 'write' }, access.frozen, held);
    } catch (error) {
      options.log.warn('sim.openFailed', { project, error: errorText(error) });
      refuse('unknownProject', access.person.login);
    }
  };
  const handle = async (request: IncomingMessage, response: ServerResponse, path: string) => {
    if (request.method === 'GET' && path === '/healthz') json(response, 200, { status: 'ok', documents: hocuspocus.getDocumentsCount(), connections: hocuspocus.getConnectionsCount(), rooms: sims.stats().rooms });
    else if (request.method === 'GET' && path === '/__auth') await exchangeTicket(request, response, options);
    else if (path.startsWith('/svc/')) await handleService(request, response, path, { ...options, sync, sims });
    else if (path === '/blobs' || path.startsWith('/blobs/')) await handleBlobs(request, response, new URL(request.url ?? '/', 'http://filius'), options);
    else if (options.editor === undefined || !(await options.editor(request, response, path))) json(response, 404, { error: 'notFound' });
  };
  const http: Server = createServer((request, response) => {
    const path = new URL(request.url ?? '/', 'http://filius').pathname;
    handle(request, response, path).catch((error: unknown) => {
      options.log.error('http.failed', { path, error: errorText(error) });
      if (!response.headersSent) json(response, 500, { error: 'internal' });
      else response.end();
    });
  });
  http.on('upgrade', (request, socket, head) => {
    const path = new URL(request.url ?? '/', 'http://filius').pathname;
    if (path !== '/sync' && path !== '/sim') {
      refuse(socket as Socket, '404 Not Found');
      return;
    }
    const origin = request.headers.origin;
    if (origin !== undefined && !options.origins.includes(origin)) {
      options.log.warn('sync.foreignOrigin', { origin });
      refuse(socket as Socket, '403 Forbidden');
      return;
    }
    if (closing) {
      refuse(socket as Socket, '503 Service Unavailable');
      return;
    }
    if (path === '/sim')
      simSockets.handleUpgrade(request, socket, head, (ws) =>
        admit(ws, request).catch((error: unknown) => {
          options.log.error('sim.admitFailed', { error: errorText(error) });
          ws.close(1011, 'internal');
        }),
      );
    else sockets.handleUpgrade(request, socket, head, (ws) => hocuspocus.handleConnection(ws, request));
  });
  await new Promise<void>((resolve) => http.listen(options.port ?? 0, options.host ?? '0.0.0.0', resolve));
  const port = (http.address() as AddressInfo).port;
  options.log.info('server.listening', { port });
  return {
    port,
    sync,
    sims,
    async close() {
      closing = true;
      clearInterval(pings);
      await sims.close();
      simSockets.close();
      hocuspocus.closeConnections();
      // Hocuspocus' close is a message on the socket, after which a client signs in again on it: the sockets go too.
      for (const socket of sockets.clients) socket.close(1001, 'service stopping');
      // Each document is stored and unloaded once its last person has gone.
      for (let waited = 0; hocuspocus.getDocumentsCount() > 0 && waited < 10_000; waited += 50) await new Promise((resolve) => setTimeout(resolve, 50));
      sockets.close();
      await new Promise<void>((resolve) => http.close(() => resolve()));
      options.log.info('server.closed', { documents: hocuspocus.getDocumentsCount() });
    },
  };
}