import { NextRequest, NextResponse } from 'next/server';
import { initAdminPassword, verifyAdminPassword, updateLastLogin, isAdminEnabled, getAdminMeta } from '@/lib/admin/password';
import { setAdminSessionCookie, clearAdminSessionCookie, requireAdminAuth, getClientIP } from '@/lib/admin/session';
import { checkRateLimit } from '@/lib/admin/rate-limit';
import { auditLog } from '@/lib/admin/audit';
import { logger } from '@/lib/logger';
import { getStalwartCredentials } from '@/lib/stalwart/credentials';

/**
 * Check if the current user is a Stalwart admin by attempting an
 * admin-only JMAP method call. Stalwart v0.16 removed the REST management
 * API (including the /api/account permissions endpoint) and exposes all
 * administration through JMAP under the `urn:stalwart:jmap` capability.
 *
 * `x:Account/query` requires the `sysAccountQuery` permission, which is
 * granted to admins and tenant admins. If the method returns a result,
 * the caller is an admin; a method error (typically `forbidden`) means
 * the caller is a regular user.
 *
 * Results are cached briefly per (server, user) — the admin panel's
 * layout and dashboard page between them trigger this three times on
 * every navigation, and admin status does not change on that timescale.
 */
const ADMIN_CHECK_CACHE_MS = 60_000;
const ADMIN_CHECK_TIMEOUT_MS = 10_000;
const adminCheckCache = new Map<string, { value: boolean; expires: number }>();

async function fetchWithTimeout(url: string, init: RequestInit): Promise<Response> {
  const controller = new AbortController();
  const timer = setTimeout(() => controller.abort(), ADMIN_CHECK_TIMEOUT_MS);
  try {
    return await fetch(url, { ...init, signal: controller.signal });
  } finally {
    clearTimeout(timer);
  }
}

async function checkStalwartAdmin(request: NextRequest): Promise<boolean> {
  const creds = await getStalwartCredentials(request);
  if (!creds) return false;

  const cacheKey = `${creds.serverUrl} ${creds.username}`;
  const cached = adminCheckCache.get(cacheKey);
  if (cached && cached.expires > Date.now()) return cached.value;

  const isAdmin = await runStalwartAdminCheck(creds);
  adminCheckCache.set(cacheKey, { value: isAdmin, expires: Date.now() + ADMIN_CHECK_CACHE_MS });
  return isAdmin;
}

async function runStalwartAdminCheck(
  creds: { serverUrl: string; authHeader: string; username: string },
): Promise<boolean> {
  try {
    const sessionRes = await fetchWithTimeout(`${creds.serverUrl}/.well-known/jmap`, {
      method: 'GET',
      headers: { 'Authorization': creds.authHeader },
    });
    if (!sessionRes.ok) {
      logger.info('Stalwart admin check (session)', { username: creds.username, status: sessionRes.status, isAdmin: false });
      return false;
    }

    const session = await sessionRes.json() as {
      primaryAccounts?: Record<string, string>;
    };
    const accountId = session.primaryAccounts?.['urn:stalwart:jmap']
      ?? session.primaryAccounts?.['urn:ietf:params:jmap:mail']
      ?? (session.primaryAccounts ? Object.values(session.primaryAccounts)[0] : undefined);
    if (!accountId) {
      logger.info('Stalwart admin check (no account)', { username: creds.username, isAdmin: false });
      return false;
    }

    // Hit the externally-reachable URL, not session.apiUrl — Stalwart
    // advertises its internal bind address (e.g. http://host:8080/jmap/)
    // which may not be routable from this process.
    const jmapRes = await fetchWithTimeout(`${creds.serverUrl}/jmap/`, {
      method: 'POST',
      headers: {
        'Authorization': creds.authHeader,
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        using: ['urn:ietf:params:jmap:core', 'urn:stalwart:jmap'],
        methodCalls: [['x:Account/query', { accountId, limit: 1 }, '0']],
      }),
    });

    if (!jmapRes.ok) {
      logger.info('Stalwart admin check (jmap)', { username: creds.username, status: jmapRes.status, isAdmin: false });
      return false;
    }

    const data = await jmapRes.json() as {
      methodResponses?: Array<[string, Record<string, unknown>, string]>;
    };
    const first = data.methodResponses?.[0];
    const isAdmin = !!first && first[0] === 'x:Account/query';
    logger.info('Stalwart admin check', { username: creds.username, isAdmin });
    return isAdmin;
  } catch (error) {
    logger.debug('Stalwart admin check error', { error: error instanceof Error ? error.message : 'Unknown' });
    return false;
  }
}

/**
 * POST /api/admin/auth - Login
 */
export async function POST(request: NextRequest) {
  try {
    const ip = getClientIP(request);
    const body = await request.json();

    // Stalwart-based admin authentication
    if (body.stalwartAuth === true) {
      const isStalwartAdmin = await checkStalwartAdmin(request);
      if (!isStalwartAdmin) {
        await auditLog('admin.login_failed', { method: 'stalwart' }, ip);
        return NextResponse.json({ error: 'Not a Stalwart admin' }, { status: 403 });
      }

      await setAdminSessionCookie();
      await auditLog('admin.login', { method: 'stalwart' }, ip);
      return NextResponse.json({ ok: true });
    }

    // Password-based admin authentication
    await initAdminPassword();
    if (!isAdminEnabled()) {
      return NextResponse.json({ error: 'Admin dashboard is not configured' }, { status: 404 });
    }

    // Rate limit check
    const limit = checkRateLimit(ip);
    if (!limit.allowed) {
      const retryAfter = Math.ceil(limit.retryAfterMs / 1000);
      await auditLog('admin.login_blocked', { reason: 'rate_limit' }, ip);
      return NextResponse.json(
        { error: 'Too many login attempts. Try again later.' },
        { status: 429, headers: { 'Retry-After': String(retryAfter) } }
      );
    }

    const { password } = body;

    if (!password || typeof password !== 'string') {
      return NextResponse.json({ error: 'Password is required' }, { status: 400 });
    }

    const valid = await verifyAdminPassword(password);
    if (!valid) {
      await auditLog('admin.login_failed', {}, ip);
      logger.warn('Admin login failed', { ip });
      return NextResponse.json({ error: 'Invalid password' }, { status: 401 });
    }

    await setAdminSessionCookie();
    await updateLastLogin();
    await auditLog('admin.login', {}, ip);

    return NextResponse.json({ ok: true });
  } catch (error) {
    logger.error('Admin login error', { error: error instanceof Error ? error.message : 'Unknown error' });
    return NextResponse.json({ error: 'Internal server error' }, { status: 500 });
  }
}

/**
 * GET /api/admin/auth - Check session status
 * Also checks if the user is a Stalwart admin (admin panel enabled even without password).
 */
export async function GET(request: NextRequest) {
  try {
    await initAdminPassword();
    const adminEnabled = isAdminEnabled();
    const isStalwartAdmin = await checkStalwartAdmin(request);

    // If neither password-based admin nor Stalwart admin, admin is disabled
    if (!adminEnabled && !isStalwartAdmin) {
      return NextResponse.json({ enabled: false, authenticated: false, stalwartAdmin: false }, {
        headers: { 'Cache-Control': 'no-store' },
      });
    }

    const result = await requireAdminAuth();
    if ('error' in result) {
      return NextResponse.json({
        enabled: adminEnabled,
        authenticated: false,
        stalwartAdmin: isStalwartAdmin,
      }, {
        headers: { 'Cache-Control': 'no-store' },
      });
    }

    const meta = getAdminMeta();
    return NextResponse.json({
      enabled: adminEnabled,
      authenticated: true,
      stalwartAdmin: isStalwartAdmin,
      lastLogin: meta?.lastLogin,
      passwordChangedAt: meta?.passwordChangedAt,
    }, {
      headers: { 'Cache-Control': 'no-store' },
    });
  } catch (error) {
    logger.error('Admin status error', { error: error instanceof Error ? error.message : 'Unknown error' });
    return NextResponse.json({ error: 'Internal server error' }, { status: 500 });
  }
}

/**
 * DELETE /api/admin/auth - Logout
 */
export async function DELETE(request: NextRequest) {
  try {
    const ip = getClientIP(request);
    await clearAdminSessionCookie();
    await auditLog('admin.logout', {}, ip);
    return NextResponse.json({ ok: true });
  } catch (error) {
    logger.error('Admin logout error', { error: error instanceof Error ? error.message : 'Unknown error' });
    return NextResponse.json({ error: 'Internal server error' }, { status: 500 });
  }
}