'use strict';

// Unauthenticated endpoints backing the two invite link types. Everything here
// is reachable without a login, so each handler is rate limited and every token
// is looked up by hash.

const express = require('express');
const config = require('../config');
const { invites, inviteUsable, clients, audit } = require('../db');
const { uuid, randomToken, sha256 } = require('../crypto');
const tickets = require('../tickets');

const router = express.Router();

/* Crude per-IP limiter: enough to make token guessing pointless without pulling
   in a dependency. Buckets refill continuously and are swept on a timer. */
const buckets = new Map();
const LIMIT = 30;
const WINDOW_MS = 60_000;

function rateLimit(req, res, next) {
  const ip = req.ip || 'unknown';
  const now = Date.now();
  const b = buckets.get(ip) || { count: 0, resetAt: now + WINDOW_MS };
  if (b.resetAt < now) {
    b.count = 0;
    b.resetAt = now + WINDOW_MS;
  }
  b.count++;
  buckets.set(ip, b);
  if (b.count > LIMIT) {
    return res.status(429).json({ error: 'too many attempts, wait a minute' });
  }
  next();
}

setInterval(() => {
  const now = Date.now();
  for (const [ip, b] of buckets) if (b.resetAt < now) buckets.delete(ip);
}, WINDOW_MS).unref?.();

router.use(rateLimit);

function lookup(token) {
  const invite = invites.findByHash(sha256(String(token || '')));
  const usable = inviteUsable(invite);
  return { invite, usable };
}

/** What a landing page needs to render, without consuming a use. */
router.get('/invite/:token', (req, res) => {
  const { invite, usable } = lookup(req.params.token);
  if (!invite) return res.status(404).json({ error: 'this link is not valid' });

  const client = invite.client_id ? clients.get(invite.client_id) : null;
  res.json({
    kind: invite.kind,
    label: invite.label,
    role: invite.role,
    clientName: client ? client.name : null,
    expiresAt: invite.expires_at,
    usable: usable.ok,
    reason: usable.ok ? null : usable.reason,
  });
});

/**
 * A machine redeems an enrollment link. Returns an agent key, shown once and
 * stored only as a hash — the agent keeps it and reconnects with it forever.
 */
router.post('/enroll', (req, res) => {
  const body = req.body || {};
  const { invite, usable } = lookup(body.token);
  if (!invite || invite.kind !== 'enroll') return res.status(404).json({ error: 'this enrollment link is not valid' });
  if (!usable.ok) return res.status(410).json({ error: `this enrollment link is ${usable.reason}` });

  const prefill = invite.prefill ? JSON.parse(invite.prefill) : {};
  const hostname = String(body.hostname || '').trim().slice(0, 100) || 'unnamed machine';
  const agentKey = randomToken(32);

  let client;
  if (invite.client_id) {
    // Re-enrolment of an existing entry: keep its grants and history, new key.
    client = clients.get(invite.client_id);
    if (!client) return res.status(410).json({ error: 'the client this link pointed at has been deleted' });
    clients.update(client.id, {
      mode: 'agent',
      agent_key_hash: sha256(agentKey),
      hostname,
      os: body.os ? String(body.os).slice(0, 60) : null,
      agent_version: body.agentVersion ? String(body.agentVersion).slice(0, 30) : null,
      port: Number(body.vncPort) || client.port || 5900,
      enrolled_at: Date.now(),
      last_ip: req.ip,
    });
  } else {
    let name = (prefill.name || body.name || hostname).trim().slice(0, 100);
    // Names are how operators pick a machine, so keep them unique.
    if (clients.getByName(name)) {
      let n = 2;
      while (clients.getByName(`${name} (${n})`)) n++;
      name = `${name} (${n})`;
    }
    client = clients.create({
      id: uuid(),
      name,
      mode: 'agent',
      host: null,
      port: Number(body.vncPort) || 5900,
      agent_key_hash: sha256(agentKey),
      require_consent: prefill.requireConsent ? 1 : 0,
      tags: prefill.tags || '',
      os: body.os ? String(body.os).slice(0, 60) : null,
      hostname,
      agent_version: body.agentVersion ? String(body.agentVersion).slice(0, 30) : null,
      enrolled_at: Date.now(),
      created_by: invite.created_by,
    });
  }

  invites.consume(invite.id);
  audit(invite.created_by, 'client.enroll', client.id, { name: client.name, hostname, ip: req.ip });

  res.status(201).json({
    clientId: client.id,
    name: client.name,
    agentKey,
    requireConsent: !!client.require_consent,
  });
});

/**
 * A person redeems a support link. No login: the invite itself is the
 * authorisation, and it fixes both the target machine and the role.
 */
router.post('/session/:token', (req, res) => {
  if (!config.allowSessionInvites) return res.status(403).json({ error: 'session invites are disabled' });

  const { invite, usable } = lookup(req.params.token);
  if (!invite || invite.kind !== 'session') return res.status(404).json({ error: 'this link is not valid' });
  if (!usable.ok) return res.status(410).json({ error: `this link is ${usable.reason}` });

  const client = clients.get(invite.client_id);
  if (!client) return res.status(410).json({ error: 'the machine this link pointed at has been removed' });

  const displayName = String((req.body || {}).name || '').trim().slice(0, 60);
  const username = displayName ? `invite:${displayName}` : `invite:${invite.label || invite.id.slice(0, 8)}`;
  const role = invite.role === 'operator' ? 'operator' : 'viewer';
  const sessionId = uuid();

  const ticket = tickets.issue({
    sessionId,
    clientId: client.id,
    username,
    role,
    source: 'invite',
    inviteId: invite.id,
  });

  invites.consume(invite.id);
  audit(username, 'invite.redeem', invite.id, { clientId: client.id, role, ip: req.ip });

  res.json({
    ticket: ticket.token,
    expiresIn: ticket.expiresIn,
    clientName: client.name,
    role,
    sessionId,
  });
});

module.exports = { router };