/**
 * Admin route handlers.
 *
 * Everything here is form-based so a JS-off browser still works. The one GET
 * that mutates state (the login POST → session cookie) is a form submission;
 * every other mutation POSTs and redirects to the GET it changed.
 *
 * Pages come from admin-pages.js; this file is the glue between HTTP and the
 * DB / session.
 */

import { layout } from './layout.js';
import {
  newChallenge, verifyLogin, readSession, clearCookie, adminPublisher, loginMessage,
} from './admin-session.js';
import {
  allListingsIncludingWithdrawn, allActiveListings, withdrawListing, getListing,
  countActive, recentAudit as recentAuditRows,
} from './db.js';
import { allModes, setMode, MODES } from './modes.js';
import { CATEGORIES, countsByCategory } from './pages-browse.js';
import { logAudit } from './audit.js';
import {
  loginPage, dashboardPage, listingsPage, modesPage, auditPage,
} from './admin-pages.js';

/* ----------------- dispatch (called from server.js) ----------------- */

/**
 * Admin router. Returns true if it handled the request. The caller falls
 * through to the regular router if we return false.
 */
export async function handleAdmin(req, res, url) {
  // /admin/login (GET + POST) is the only path accessible without a session.
  if (url === '/admin/login') {
    if (req.method === 'POST') return doLogin(req, res);
    return renderPage(res, loginPage({
      challenge: newChallenge(adminPublisher()),
      name: adminPublisher() || '(ADMIN_PUBLISHER env not set)',
    }));
  }
  if (url === '/admin/logout' && req.method === 'POST') {
    return doLogout(res);
  }

  // Everything else requires a session.
  const session = readSession(req);
  if (!session) {
    res.writeHead(302, { location: '/admin/login' });
    return res.end();
  }

  if (url === '/admin' || url === '/admin/') return showDashboard(res, session);
  if (url === '/admin/listings') return showListings(res, session);
  if (url === '/admin/modes') {
    if (req.method === 'POST') return saveModes(req, res, session);
    return showModes(res, session);
  }
  if (url === '/admin/audit') return showAudit(res, session);

  const withdrawMatch = url.match(/^\/admin\/listings\/([^/]+)\/([^/]+)\/withdraw$/);
  if (withdrawMatch && req.method === 'POST') {
    return doWithdraw(req, res, session, `${decodeURIComponent(withdrawMatch[1])}/${decodeURIComponent(withdrawMatch[2])}`);
  }

  return notFoundHtml(res);
}

/* ----------------- login + logout ----------------- */

async function doLogin(req, res) {
  const form = await readForm(req);
  const result = await verifyLogin({
    challenge: String(form.challenge || ''),
    signature: String(form.signature || ''),
  });
  if (!result.ok) {
    return renderPage(res, loginPage({
      challenge: newChallenge(adminPublisher()),
      name: adminPublisher(),
      error: result.reason,
    }), 400);
  }

  logAudit({ actor: result.admin.name, action: 'login' });

  res.writeHead(302, {
    location: '/admin',
    'set-cookie': result.cookie,
  });
  res.end();
}

function doLogout(res) {
  res.writeHead(302, {
    location: '/admin/login',
    'set-cookie': clearCookie(),
  });
  res.end();
}

/* ----------------- GET pages ----------------- */

function showDashboard(res, session) {
  const counts = countsByCategory();
  const total = countActive();
  const modes = allModes(CATEGORIES.map((c) => c.slug));
  const recentListings = allActiveListings().slice(0, 10);
  const recentAudit = recentAuditRows(20);
  renderPage(res, dashboardPage({ session, counts, total, modes, recentListings, recentAudit }));
}

function showListings(res, session) {
  const rows = allListingsIncludingWithdrawn();
  renderPage(res, listingsPage({ session, rows }));
}

function showModes(res, session) {
  const modes = allModes(CATEGORIES.map((c) => c.slug));
  renderPage(res, modesPage({ session, modes }));
}

function showAudit(res, session) {
  const entries = recentAuditRows(200);
  renderPage(res, auditPage({ session, entries }));
}

/* ----------------- POST actions ----------------- */

async function doWithdraw(req, res, session, id) {
  const row = getListing(id);
  if (!row) return notFoundHtml(res);
  const changed = withdrawListing(id, new Date().toISOString());
  if (changed) {
    logAudit({
      actor: session.name,
      action: 'withdraw_listing',
      target: id,
      details: { category: row.category, publisher: row.publisher },
    });
  }
  res.writeHead(302, { location: '/admin/listings' });
  res.end();
}

async function saveModes(req, res, session) {
  const form = await readForm(req);

  // Global first — the per-category reads depend on the current global.
  const g = String(form.global || '');
  if (MODES.includes(g)) {
    setMode({ category: null, value: g, actor: session.name });
  }

  for (const c of CATEGORIES) {
    const v = String(form[`cat_${c.slug}`] || '');
    // v === '' means "inherits global" — pass empty value to clear override.
    setMode({ category: c.slug, value: v, actor: session.name });
  }

  res.writeHead(302, { location: '/admin/modes' });
  res.end();
}

/* ----------------- helpers ----------------- */

function renderPage(res, page, status = 200) {
  const html = layout(page);
  res.writeHead(status, {
    'content-type': 'text/html; charset=utf-8',
    'cache-control': 'no-store',
  });
  res.end(html);
}

function notFoundHtml(res) {
  const page = {
    title: 'Not here',
    description: 'The requested admin page does not exist.',
    body: `<header class="hero compact"><h1>Not here</h1></header>
      <div class="wrap"><section class="plain"><p>Go <a href="/admin">home</a>.</p></section></div>`,
  };
  renderPage(res, page, 404);
}

async function readForm(req) {
  const chunks = [];
  let total = 0;
  for await (const chunk of req) {
    total += chunk.length;
    if (total > 64 * 1024) throw new Error('form too large');
    chunks.push(chunk);
  }
  const body = Buffer.concat(chunks).toString('utf8');
  const params = new URLSearchParams(body);
  const out = {};
  for (const [k, v] of params) out[k] = v;
  return out;
}