import { createServerClient } from '@supabase/ssr'
import { NextResponse, type NextRequest } from 'next/server'
import { shouldEnforceMfa } from '@/lib/auth/mfa'
import { apiPathSkipsMfaGate } from '@/lib/auth/api-mfa-gate'
import { DEFAULT_LOCALE, LOCALE_COOKIE, isLocale } from '@/i18n/config'
import { userHasPassword } from '@/lib/auth/has-password'
import { safeReturnTo } from '@/lib/auth/safe-return-to'
import {
  apiRequestSkipsSessionTimeout,
  createSessionTimeoutState,
  evaluateSessionTimeout,
  fetchAutoLogoutPreference,
  getSessionTimeoutConfig,
  sessionStateMatchesUser,
  sessionStateNeedsRemint,
  sessionTimeoutClearCookieOptions,
  sessionTimeoutCookieOptions,
  signSessionTimeoutState,
  verifySessionTimeoutState,
} from '@/lib/auth/session-timeout'
import {
  isSessionAuthMethod,
  SESSION_AUTH_METHOD_HINT_COOKIE,
  SESSION_TIMEOUT_COOKIE,
  SESSION_TIMEOUT_REASON_HEADER,
  type SessionAuthMethod,
  type SessionTimeoutReason,
} from '@/lib/auth/session-timeout-shared'

export async function updateSession(request: NextRequest) {
  let supabaseResponse = NextResponse.next({
    request,
  })

  const supabase = createServerClient(
    process.env.NEXT_PUBLIC_SUPABASE_URL!,
    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
    {
      cookies: {
        getAll() {
          return request.cookies.getAll()
        },
        setAll(cookiesToSet) {
          cookiesToSet.forEach(({ name, value }) =>
            request.cookies.set(name, value)
          )
          supabaseResponse = NextResponse.next({
            request,
          })
          cookiesToSet.forEach(({ name, value, options }) =>
            supabaseResponse.cookies.set(name, value, options)
          )
        },
      },
    }
  )

  // IMPORTANT: Avoid writing any logic between createServerClient and
  // supabase.auth.getUser(). A simple mistake could make it very hard to debug
  // issues with users being randomly logged out.

  const {
    data: { user },
    error: authError,
  } = await supabase.auth.getUser()

  // Get the pathname
  const pathname = request.nextUrl.pathname

  // If the refresh token is stale/invalid, clear the session cookies so the
  // browser stops sending them on every request, INCLUDING /api requests,
  // which previously returned before this cleanup and replayed the dead
  // token forever. Skip on auth routes, the callback needs PKCE cookies
  // intact. scope: 'local' only clears cookies: the refresh token is already
  // dead server-side, and the default global-revoke round-trip re-triggers
  // the failed refresh, the exact AuthApiError this cleans up after.
  if (authError && !user && !pathname.startsWith('/auth')) {
    try {
      await supabase.auth.signOut({ scope: 'local' })
    } catch (signOutError) {
      // Expected session expiry, not a runtime error.
      console.warn('[middleware] session cleanup after stale refresh token failed', signOutError)
    }
  }

  const timeoutConfig = getSessionTimeoutConfig()
  const hasAuthorizationHeader = request.headers.get('authorization') !== null

  if (!user) {
    clearSessionTimeoutCookies(request, supabaseResponse)
  } else if (
    timeoutConfig.enabled &&
    !apiRequestSkipsSessionTimeout(pathname, hasAuthorizationHeader)
  ) {
    const encodedState = request.cookies.get(SESSION_TIMEOUT_COOKIE)?.value
    const sessionId = await getSupabaseSessionId(supabase)
    const verifiedState = await verifySessionTimeoutState(encodedState)

    if (encodedState && !verifiedState) {
      await signOutTimedOutSession(supabase)
      return sessionTimeoutResponse(
        request,
        supabaseResponse,
        'absolute',
        'password',
      )
    }

    const stateMatches =
      verifiedState !== null &&
      sessionStateMatchesUser(verifiedState, user.id, sessionId)

    if (
      !verifiedState ||
      !stateMatches ||
      sessionStateNeedsRemint(verifiedState)
    ) {
      const hintedMethod = request.cookies.get(
        SESSION_AUTH_METHOD_HINT_COOKIE,
      )?.value
      const method = isSessionAuthMethod(hintedMethod)
        ? hintedMethod
        : 'password'
      const autoLogout = await fetchAutoLogoutPreference(supabase, user.id)

      // Unknown preference (failed read): mint nothing, so no fail-open
      // snapshot gets persisted; the next request retries the read.
      if (autoLogout !== null) {
        // A matching pre-toggle cookie keeps its timers: upgrading the shape
        // must not restart the absolute window.
        const state = verifiedState && stateMatches
          ? { ...verifiedState, autoLogout }
          : createSessionTimeoutState({
              userId: user.id,
              sessionId,
              method,
              autoLogout,
            })
        const signedState = await signSessionTimeoutState(state)

        if (signedState) {
          request.cookies.set(SESSION_TIMEOUT_COOKIE, signedState)
          supabaseResponse.cookies.set(
            SESSION_TIMEOUT_COOKIE,
            signedState,
            sessionTimeoutCookieOptions(),
          )
          clearAuthMethodHint(request, supabaseResponse)
        }
      }
    } else {
      const timeoutReason = evaluateSessionTimeout(
        verifiedState,
        timeoutConfig,
      )
      if (timeoutReason) {
        await signOutTimedOutSession(supabase)
        return sessionTimeoutResponse(
          request,
          supabaseResponse,
          timeoutReason,
          verifiedState.method,
        )
      }
    }
  }

  // ── API routes ──────────────────────────────────────────────────────────
  // API routes authenticate themselves (requireAuth, API-key Bearer, cron
  // secret, webhook signatures). Middleware runs on them for ONE reason: to
  // close the MFA gap. Many legacy routes hand-roll supabase.auth.getUser()
  // instead of requireAuth(), so without this an authenticated-but-not-MFA-
  // verified (AAL1) cookie session could reach them on the hosted product.
  // Gate ONLY cookie sessions. Bearer-auth SURFACES (/api/v1, the MCP
  // endpoint) and the AAL1 escape-hatch / OAuth routes pass straight through
  // (see apiPathSkipsMfaGate): header presence alone never skips the gate,
  // since the header is attacker-controlled and cookie-authenticated routes
  // ignore it. Pure Bearer callers (cron, webhooks) carry no cookie session,
  // so the `user` guard below already excludes them. Everything else about
  // /api auth stays the route's own responsibility.
  if (pathname.startsWith('/api')) {
    const skipMfaGate = apiPathSkipsMfaGate(
      pathname,
      hasAuthorizationHeader,
    )
    if (!skipMfaGate && user && shouldEnforceMfa(user)) {
      const { data: aal } =
        await supabase.auth.mfa.getAuthenticatorAssuranceLevel()
      if (aal?.nextLevel === 'aal2' && aal?.currentLevel === 'aal1') {
        return NextResponse.json({ error: 'MFA-verifiering krävs.' }, { status: 403 })
      }
    }
    return supabaseResponse
  }

  // Invite pages: accessible to everyone, signed in or not. A user who
  // already has an account and is signed in should still be able to land on
  // /invite/[token] to accept the invite with one click (see
  // app/invite/[token]/page.tsx). If we bounce them to '/', they never see
  // the invite at all.
  if (pathname.startsWith('/invite')) {
    return supabaseResponse
  }

  // Public payslip pages, the token in the URL is the authentication
  // (resolved server-side against salary_payslip_links). Employees have no
  // account; bouncing them to /login would make every emailed payslip link
  // dead. See app/payslip/[token]/page.tsx.
  if (pathname.startsWith('/payslip')) {
    return supabaseResponse
  }

  // Reset-password is reachable in both auth states. The recovery flow lands
  // here with a fresh session (created by the OTP exchange in /auth/callback)
  // precisely so the user can call supabase.auth.updateUser({ password }). If
  // we bounce authenticated users to '/', the recovery email link silently
  // fails. An already-logged-in user typing /reset-password directly just gets
  // the same "change password" experience as in settings: no security loss.
  if (pathname.startsWith('/reset-password')) {
    return supabaseResponse
  }

  // Public agent-discovery + API docs surfaces. /llms.txt and /llms-full.txt
  // exist FOR anonymous consumers (the llms.txt convention targets logged-out
  // crawlers and IDE agents), and /docs is the public API documentation the
  // OpenAPI spec and the installable accounted-api skill link to. None of it
  // reads the session. Without this branch every anonymous hit 307-bounced to
  // /login, which silently broke agent discovery on the hosted product
  // (openapi.json only escaped because the proxy matcher skips .json paths).
  // Logged-in users fall through to the same content: no redirect either way.
  if (
    pathname === '/llms.txt' ||
    pathname === '/llms-full.txt' ||
    pathname === '/docs' ||
    pathname.startsWith('/docs/')
  ) {
    return supabaseResponse
  }

  // Public auth routes: allow access
  if (
    pathname.startsWith('/login') ||
    pathname.startsWith('/register') ||
    pathname.startsWith('/auth') ||
    pathname.startsWith('/sandbox')
  ) {
    // If user is logged in and trying to access auth pages, redirect to the
    // destination the auth page would have sent them to, dashboard otherwise.
    // /login?next=… is set by callers like the MCP OAuth authorize endpoint
    // and by the bounce below; discarding the whole query string here
    // stranded an already-signed-in user on the dashboard instead of the
    // deep link they clicked. Only /login and /register carry `next`;
    // /auth (the PKCE callback) and /sandbox bounce to '/' exactly as before.
    if (user) {
      const carriesDestination =
        pathname.startsWith('/login') || pathname.startsWith('/register')
      const destination = carriesDestination
        ? safeReturnTo(request.nextUrl.searchParams.get('next'), '/')
        : '/'
      return NextResponse.redirect(new URL(destination, request.url))
    }
    return supabaseResponse
  }

  // Protected routes - require authentication
  if (!user) {
    return bounceToAuth(request, '/login')
  }

  // /mfa/enroll: gate behind has-password. BankID-only users who reach this
  // page can lock themselves out: Supabase requires AAL2 to change password
  // or unenroll MFA, and AAL2 needs a prior password sign-in. Force them to
  // set a password first. The /account/set-password page does that and routes
  // back here via ?returnTo. Thread the inner returnTo through so the user
  // ends up on their original destination after the full chain completes.
  if (pathname.startsWith('/mfa/enroll')) {
    if (!userHasPassword(user)) {
      const innerReturnTo = request.nextUrl.searchParams.get('returnTo')
      const mfaTarget = `/mfa/enroll${
        innerReturnTo ? `?returnTo=${encodeURIComponent(innerReturnTo)}` : ''
      }`
      return NextResponse.redirect(
        new URL(
          `/account/set-password?returnTo=${encodeURIComponent(mfaTarget)}`,
          request.url,
        ),
      )
    }
    return supabaseResponse
  }

  // Other MFA pages: accessible to authenticated users (AAL1+), skip MFA enforcement
  if (pathname.startsWith('/mfa/')) {
    return supabaseResponse
  }

  // /account/set-password is the escape hatch from the BankID/MFA lockout
  // and must be reachable even when the user has no company yet (e.g. mid-
  // onboarding) and is at AAL1.
  if (pathname.startsWith('/account/set-password')) {
    return supabaseResponse
  }

  // Resolve the active company at most once per request: both the MFA
  // enrollment gate and the company-context block below need it, and the
  // resolution costs DB round trips.
  let resolvedCompany: {
    companyId: string | null
    locale: string | null
    degraded: boolean
  } | null = null
  const resolveCompanyOnce = async () =>
    (resolvedCompany ??= await resolveCompanyForMiddleware(supabase, user.id, request))

  // MFA enforcement (application-side only, not RLS)
  if (shouldEnforceMfa(user)) {
    const { data: aal } = await supabase.auth.mfa.getAuthenticatorAssuranceLevel()

    // User has MFA enrolled but hasn't verified this session → redirect to verify
    if (aal?.nextLevel === 'aal2' && aal?.currentLevel === 'aal1') {
      return bounceToAuth(request, '/mfa/verify')
    }

    // MFA required but user has no factor enrolled yet → force enrollment
    // Skip for users with no companies (still setting up)
    const { companyId: companyIdForMfa } = await resolveCompanyOnce()
    if (companyIdForMfa) {
      const { data: factors } = await supabase.auth.mfa.listFactors()
      const hasVerifiedFactor = factors?.totp?.some(f => f.status === 'verified')

      if (!hasVerifiedFactor) {
        return bounceToAuth(request, '/mfa/enroll')
      }
    }
  }

  // Forward the pathname so server layouts can branch on it (e.g. render a
  // no-company shell for /settings/account).
  supabaseResponse.headers.set('x-pathname', pathname)

  // Company context resolution
  const cookieCompanyId = request.cookies.get('gnubok-company-id')?.value
  const { companyId, locale: dbLocale, degraded } = await resolveCompanyOnce()

  // If the cookie pointed at a company we can no longer resolve (e.g.
  // archived), clear it so the browser stops sending it. Never on degraded
  // resolution: a transient query failure must not wipe a valid cookie.
  if (!degraded && cookieCompanyId && cookieCompanyId !== companyId) {
    supabaseResponse.cookies.set('gnubok-company-id', '', { path: '/', maxAge: 0 })
  }

  // Sync the locale cookie from user_preferences. This keeps next-intl's
  // request config (which reads the cookie) consistent with the DB value
  // without forcing every RSC render to query the database itself.
  const cookieLocale = request.cookies.get(LOCALE_COOKIE)?.value
  const effectiveLocale = isLocale(dbLocale) ? dbLocale : DEFAULT_LOCALE
  if (!degraded && cookieLocale !== effectiveLocale) {
    supabaseResponse.cookies.set(LOCALE_COOKIE, effectiveLocale, {
      path: '/',
      sameSite: 'lax',
      secure: process.env.NODE_ENV === 'production',
      maxAge: 60 * 60 * 24 * 365,
    })
  }

  // Routes that stay accessible when the user has no active company.
  // Needed so a user who archived their last company can still delete
  // their account without being trapped on /onboarding forever.
  const isNoCompanyAllowed =
    pathname.startsWith('/onboarding') ||
    pathname.startsWith('/select-company') ||
    pathname.startsWith('/settings/account') ||
    pathname.startsWith('/api/account/') ||
    pathname.startsWith('/api/company')

  // No companies: redirect to the picker if we have BankID enrichment for
  // this user, otherwise the manual wizard. Either way, allow the escape-hatch
  // routes to pass through.
  if (!companyId) {
    if (isNoCompanyAllowed) {
      return supabaseResponse
    }

    // Degraded resolution (a query FAILED, as opposed to returning no rows)
    // means the user's companies are unknown, not absent. Fail open: pass
    // the request through and let the layout's own resolution retry or
    // surface an error. Redirecting here showed fully onboarded users the
    // onboarding wizard again on a transient failure (issue #1053).
    if (degraded) {
      return supabaseResponse
    }

    // Enrichment lives in the user-keyed `bankid_enrichment` table (migration
    // 20260506160000), it cannot live in extension_data, which is
    // company-scoped, and the user has no company yet on this path.
    const { data: enrichmentRow } = await supabase
      .from('bankid_enrichment')
      .select('user_id')
      .eq('user_id', user.id)
      .maybeSingle()

    const destination = enrichmentRow ? '/select-company' : '/onboarding'
    return NextResponse.redirect(new URL(destination, request.url))
  }

  // Set company cookie on the response so downstream requests have it
  supabaseResponse.cookies.set('gnubok-company-id', companyId, {
    path: '/',
    httpOnly: true,
    secure: process.env.NODE_ENV === 'production',
    sameSite: 'lax',
    maxAge: 60 * 60 * 24 * 365,
  })

  // Allow access to onboarding (for adding new companies), select-company, and companies/new
  if (pathname.startsWith('/select-company') || pathname.startsWith('/companies/new') || pathname.startsWith('/onboarding')) {
    return supabaseResponse
  }

  return supabaseResponse
}

async function getSupabaseSessionId(
  supabase: ReturnType<typeof createServerClient>,
): Promise<string | null> {
  if (typeof supabase.auth.getClaims !== 'function') return null

  try {
    const { data } = await supabase.auth.getClaims()
    return typeof data?.claims?.session_id === 'string'
      ? data.claims.session_id
      : null
  } catch (error) {
    console.warn('[middleware] could not resolve Supabase session id', error)
    return null
  }
}

async function signOutTimedOutSession(
  supabase: ReturnType<typeof createServerClient>,
): Promise<void> {
  try {
    await supabase.auth.signOut({ scope: 'local' })
  } catch (error) {
    console.warn('[middleware] timed-out session revocation failed', error)
  }
}

function clearAuthMethodHint(
  request: NextRequest,
  response: NextResponse,
): void {
  if (!request.cookies.has(SESSION_AUTH_METHOD_HINT_COOKIE)) return
  request.cookies.delete(SESSION_AUTH_METHOD_HINT_COOKIE)
  response.cookies.set(SESSION_AUTH_METHOD_HINT_COOKIE, '', {
    path: '/',
    maxAge: 0,
    sameSite: 'lax',
    secure: process.env.NODE_ENV === 'production',
  })
}

function clearSessionTimeoutCookies(
  request: NextRequest,
  response: NextResponse,
): void {
  if (request.cookies.has(SESSION_TIMEOUT_COOKIE)) {
    request.cookies.delete(SESSION_TIMEOUT_COOKIE)
    response.cookies.set(
      SESSION_TIMEOUT_COOKIE,
      '',
      sessionTimeoutClearCookieOptions(),
    )
  }
  clearAuthMethodHint(request, response)
}

function copyResponseCookies(from: NextResponse, to: NextResponse): void {
  for (const cookie of from.cookies.getAll()) {
    to.cookies.set(cookie)
  }
}

function sessionTimeoutResponse(
  request: NextRequest,
  authResponse: NextResponse,
  reason: SessionTimeoutReason,
  method: SessionAuthMethod,
): NextResponse {
  clearSessionTimeoutCookies(request, authResponse)

  if (request.nextUrl.pathname.startsWith('/api')) {
    const response = NextResponse.json(
      {
        error: {
          code: 'SESSION_EXPIRED',
          message: reason === 'idle'
            ? 'Sessionen har upphört på grund av inaktivitet.'
            : 'Sessionen har upphört av säkerhetsskäl.',
          message_en: reason === 'idle'
            ? 'The session expired due to inactivity.'
            : 'The session expired for security reasons.',
          reason,
        },
      },
      { status: 401 },
    )
    response.headers.set(SESSION_TIMEOUT_REASON_HEADER, reason)
    response.headers.set('Cache-Control', 'no-store')
    copyResponseCookies(authResponse, response)
    return response
  }

  const url = new URL('/login', request.url)
  url.searchParams.set('reason', reason)
  url.searchParams.set('method', method)
  const destination = safeReturnTo(
    request.nextUrl.pathname + request.nextUrl.search,
    '/',
  )
  if (destination !== '/') url.searchParams.set('next', destination)

  const response = NextResponse.redirect(url)
  response.headers.set('Cache-Control', 'no-store')
  copyResponseCookies(authResponse, response)
  return response
}

/**
 * Which query parameter each auth page reads its post-auth destination from.
 * /login reads `next` (app/(auth)/login/page.tsx), the MFA pages read
 * `returnTo` (app/(auth)/mfa/verify/page.tsx, app/(auth)/mfa/enroll/page.tsx).
 * Sending the wrong name is a silent no-op, so the mapping is explicit
 * rather than guessed per call site.
 */
const AUTH_DESTINATION_PARAM = {
  '/login': 'next',
  '/mfa/verify': 'returnTo',
  '/mfa/enroll': 'returnTo',
} as const

/**
 * Bounce to an auth page, remembering where the user was heading.
 *
 * Fixes two things the hand-rolled redirects did wrong. (1) Cloning
 * `request.nextUrl` and overwriting only `pathname` carried the ORIGINAL
 * query string onto the auth page: /settings/billing?success=1 arrived as
 * /login?success=1, a stray parameter the login page never asked for. The
 * URL here is built fresh from the request origin, so it holds nothing but
 * the one parameter we set. (2) The destination itself was dropped, so
 * emailed deep links and payment returns landed on the dashboard after
 * sign-in instead of where the user was going.
 *
 * Open-redirect guard: the destination is the CURRENT request's path plus
 * query, run through `safeReturnTo`, which admits same-origin relative paths
 * only. Absolute URLs, protocol-relative `//evil.com`, and the encoded forms
 * that normalise into one are rejected, and a rejected (or absent, or
 * root) destination degrades to a bare bounce with no parameter at all.
 * Nothing attacker-supplied is reflected unvalidated.
 *
 * MFA semantics are untouched: this only decorates the URL of a redirect
 * that was going to happen anyway, on exactly the same conditions. The auth
 * pages navigate to the destination only after the step-up succeeds, and the
 * next request re-runs this same gate regardless.
 */
function bounceToAuth(
  request: NextRequest,
  target: keyof typeof AUTH_DESTINATION_PARAM,
) {
  // Absolute-path reference: replaces path AND clears query/fragment.
  const url = new URL(target, request.url)
  const destination = safeReturnTo(
    request.nextUrl.pathname + request.nextUrl.search,
    '/',
  )
  if (destination !== '/') {
    url.search = `${AUTH_DESTINATION_PARAM[target]}=${encodeURIComponent(destination)}`
  }
  return NextResponse.redirect(url)
}

/**
 * Resolve the active company for the authenticated user.
 *
 * Resolution: user_preferences → first non-archived membership.
 *
 * `user_preferences.active_company_id` is the authoritative source for
 * the active company on both the Next.js and Postgres RLS side. The
 * `gnubok-company-id` cookie is still refreshed for legacy read paths
 * but it is no longer READ here, because RLS (via
 * `current_active_company_id()`) cannot see cookies: so letting the
 * cookie override the database would re-introduce the divergence this
 * entire migration exists to fix.
 *
 * When we fall back to "first membership" (no user_preferences row yet),
 * we also upsert user_preferences so subsequent RLS lookups agree with
 * us without needing the fallback scan.
 *
 * RPC-first: `resolve_active_company()` collapses the whole resolution into
 * one round trip and is semantically identical to both the query path below
 * and `current_active_company_id()` (what RLS reads). `used_fallback` is
 * true exactly when the preference was missing, null, or stale, which is
 * exactly the condition under which the query path writes the resolved
 * company back to user_preferences: the write-back behavior is preserved.
 * Falls back to the query path on PGRST202 (self-hosted instance not
 * migrated yet, or a deploy racing the branch merge).
 *
 * Cannot use lib/company/context.ts because middleware runs on Edge.
 */
async function resolveCompanyForMiddleware(
  supabase: ReturnType<typeof createServerClient>,
  userId: string,
  _request: NextRequest
): Promise<{ companyId: string | null; locale: string | null; degraded: boolean }> {
  const { data, error } = await supabase.rpc('resolve_active_company')

  if (error) {
    if (error.code === 'PGRST202') {
      // Function not deployed here: use the query path.
      return resolveCompanyForMiddlewareViaQueries(supabase, userId, _request)
    }
    // Issue #1053: a FAILED call degrades (fail open), never reads as "no
    // companies". locale null is fine because the degraded flag already
    // suppresses the locale-cookie sync at the call site.
    console.error('[middleware] resolve_active_company rpc failed', error)
    return { companyId: null, locale: null, degraded: true }
  }

  const row = Array.isArray(data) ? data[0] : data
  if (!row) {
    // Zero rows = NULL auth.uid(); impossible for the cookie-auth middleware
    // client, so treat as degraded rather than redirecting to onboarding.
    console.error('[middleware] resolve_active_company returned no row for authenticated user')
    return { companyId: null, locale: null, degraded: true }
  }

  if (row.company_id && row.used_fallback) {
    // Write the fallback back to user_preferences so future RLS lookups see
    // the same active company without needing the fallback scan. Non-fatal
    // on failure: resolution already succeeded, but log it so silent
    // persistence failures (#701) are observable.
    const { error: writeBackError } = await supabase
      .from('user_preferences')
      .upsert(
        { user_id: userId, active_company_id: row.company_id },
        { onConflict: 'user_id' }
      )
    if (writeBackError) {
      console.error('[middleware] active company write-back failed', writeBackError)
    }
  }

  return {
    companyId: row.company_id ?? null,
    locale: row.locale ?? null,
    degraded: false,
  }
}

/**
 * Query-path resolution: the pre-RPC implementation, kept verbatim as the
 * fallback for resolveCompanyForMiddleware (see the fallback conditions
 * there).
 */
async function resolveCompanyForMiddlewareViaQueries(
  supabase: ReturnType<typeof createServerClient>,
  userId: string,
  _request: NextRequest
): Promise<{ companyId: string | null; locale: string | null; degraded: boolean }> {
  // 1. user_preferences (authoritative) + first membership, fetched in
  // parallel: the fallback query result doubles as validation when the
  // preferred company happens to be the first membership, which is the
  // common single-company case, so most requests pay one round trip
  // instead of two sequential ones.
  const [prefsRes, firstRes] = await Promise.all([
    supabase
      .from('user_preferences')
      .select('active_company_id, locale')
      .eq('user_id', userId)
      .maybeSingle(),
    supabase
      .from('company_members')
      .select('company_id, companies!inner(archived_at)')
      .eq('user_id', userId)
      .is('companies.archived_at', null)
      .order('created_at', { ascending: true })
      .limit(1)
      .maybeSingle(),
  ])

  const prefs = prefsRes.data
  const firstCompany = firstRes.data
  const locale = (prefs?.locale as string | undefined) ?? null

  // A FAILED query (as opposed to one returning no rows) means the user's
  // companies are unknown right now, not absent: flag it so the caller
  // fails open instead of redirecting to onboarding or clearing cookies
  // (issue #1053). Middleware cannot throw usefully, hence a flag.
  if (prefsRes.error || firstRes.error) {
    console.error(
      '[middleware] company resolution query failed',
      prefsRes.error ?? firstRes.error
    )
    return { companyId: null, locale, degraded: true }
  }

  if (prefs?.active_company_id) {
    if (prefs.active_company_id === firstCompany?.company_id) {
      return { companyId: firstCompany.company_id, locale, degraded: false }
    }

    const { data: membership, error: membershipError } = await supabase
      .from('company_members')
      .select('company_id, companies!inner(archived_at)')
      .eq('company_id', prefs.active_company_id)
      .eq('user_id', userId)
      .is('companies.archived_at', null)
      .maybeSingle()

    // A failed validation must not silently switch the user onto their
    // first membership (wrong company for consultants): degrade instead.
    if (membershipError) {
      console.error('[middleware] company preference validation failed', membershipError)
      return { companyId: null, locale, degraded: true }
    }

    if (membership) return { companyId: membership.company_id, locale, degraded: false }
  }

  // 2. Fallback: first non-archived membership (already fetched above)
  if (!firstCompany) return { companyId: null, locale, degraded: false }

  // Write the fallback back to user_preferences so future RLS lookups
  // see the same active company without needing this fallback scan.
  // Non-fatal on failure: resolution for this request already succeeded,
  // the write-back is an optimization, but log it so silent persistence
  // failures (#701) are observable.
  const { error: writeBackError } = await supabase
    .from('user_preferences')
    .upsert(
      { user_id: userId, active_company_id: firstCompany.company_id },
      { onConflict: 'user_id' }
    )

  if (writeBackError) {
    console.error('[middleware] active company write-back failed', writeBackError)
  }

  return { companyId: firstCompany.company_id, locale, degraded: false }
}