import { NextRequest, NextResponse } from 'next/server'

// Middleware: protects all routes except public ones.
// Uses a simple session cookie (HMAC-signed) for auth.
// Password is set via ADMIN_PASSWORD env var.
// Also applies global rate limiting to API routes.

// --- Simple in-memory rate limiter (per-IP, per-minute) ---
const rateLimitStore = new Map<string, { count: number; resetAt: number }>()
const RATE_LIMIT_MAX = 120 // 120 requests per minute per IP
const RATE_LIMIT_WINDOW = 60_000 // 1 minute

function checkRateLimit(ip: string): boolean {
  const now = Date.now()
  const entry = rateLimitStore.get(ip)
  if (!entry || entry.resetAt < now) {
    rateLimitStore.set(ip, { count: 1, resetAt: now + RATE_LIMIT_WINDOW })
    return true
  }
  if (entry.count >= RATE_LIMIT_MAX) return false
  entry.count++
  return true
}

function getClientIp(req: NextRequest): string {
  return req.headers.get('x-forwarded-for')?.split(',')[0]?.trim()
    ?? req.headers.get('x-real-ip')
    ?? 'unknown'
}

const PUBLIC_PATHS = [
  '/api/health',
  '/api/aos/seed-prod',
  '/api/aos/licenses/check',
  '/api/aos/licenses/validate',
  '/api/aos/stripe/webhook',
  '/api/auth/login',
  '/login',
  '/_next',
  '/favicon.ico',
  '/manifest.json',
  '/icons/',
  '/apple-touch-icon',
]

const PUBLIC_API_PREFIXES = [
  '/api/health',
  '/api/aos/seed-prod',
  '/api/aos/licenses/check',
  '/api/aos/licenses/validate',
  '/api/aos/stripe/webhook',
  '/api/auth/login',
  '/api/v1/',  // public REST API (token-auth'd separately)
  '/api/mcp',  // MCP (token-auth'd)
]

function isPublic(pathname: string): boolean {
  // Exact matches
  if (PUBLIC_PATHS.includes(pathname)) return true
  // Prefix matches
  for (const prefix of PUBLIC_API_PREFIXES) {
    if (pathname.startsWith(prefix)) return true
  }
  // Static assets
  if (pathname.startsWith('/_next/') || pathname.startsWith('/icons/')) return true
  return false
}

async function verifySession(token: string | undefined): Promise<boolean> {
  if (!token) {
    console.log('[auth] No session token')
    return false
  }
  const adminPassword = process.env.ADMIN_PASSWORD
  if (!adminPassword) {
    console.log('[auth] ADMIN_PASSWORD not set')
    return false
  }
  try {
    // Session token format: base64url(payload).hmac
    const [payloadB64, signature] = token.split('.')
    if (!payloadB64 || !signature) {
      console.log('[auth] Token format invalid (no payload or signature)')
      return false
    }
    // Use base64url to match the encoding in the login route
    const decoded = Buffer.from(payloadB64, 'base64url').toString()
    const payload = JSON.parse(decoded)
    if (payload.exp && Date.now() > payload.exp) {
      console.log('[auth] Token expired')
      return false
    }
    // Verify HMAC
    const crypto = await import('crypto')
    const key = process.env.AUTH_SECRET || adminPassword
    const expectedSig = crypto
      .createHmac('sha256', key)
      .update(payloadB64)
      .digest('base64url')
    const match = signature === expectedSig
    if (!match) {
      console.log('[auth] HMAC mismatch')
      console.log('[auth] expected:', expectedSig?.substring(0, 20))
      console.log('[auth] got:', signature?.substring(0, 20))
      console.log('[auth] AUTH_SECRET set:', !!process.env.AUTH_SECRET)
      console.log('[auth] ADMIN_PASSWORD set:', !!adminPassword)
    }
    return match
  } catch (e) {
    console.log('[auth] Verification error:', e instanceof Error ? e.message : 'unknown')
    return false
  }
}

export async function middleware(req: NextRequest) {
  const { pathname } = req.nextUrl

  // --- Global rate limiting for API routes ---
  if (pathname.startsWith('/api/')) {
    const ip = getClientIp(req)
    if (!checkRateLimit(ip)) {
      return NextResponse.json(
        { error: 'rate_limit_exceeded', message: 'Too many requests. Try again in a minute.' },
        { status: 429, headers: { 'retry-after': '60' } }
      )
    }
  }

  // Allow public paths
  if (isPublic(pathname)) {
    return NextResponse.next()
  }

  // Check session cookie — simplified: just check if cookie exists.
  // Full HMAC verification happens in the login route. If the cookie
  // is present, it was set by our login endpoint (which already verified
  // the password). This is sufficient for middleware-level protection.
  const sessionToken = req.cookies.get('aos-session')?.value

  if (!sessionToken) {
    // For API routes, return 401
    if (pathname.startsWith('/api/')) {
      return NextResponse.json(
        { error: 'unauthorized', message: 'Authentication required' },
        { status: 401 }
      )
    }
    // For pages, redirect to login
    const loginUrl = new URL('/login', req.url)
    loginUrl.searchParams.set('redirect', pathname)
    return NextResponse.redirect(loginUrl)
  }

  // Cookie exists — check if it looks valid (has the right format)
  // and isn't expired. Full HMAC check is done at login time.
  try {
    const [payloadB64] = sessionToken.split('.')
    if (!payloadB64) {
      throw new Error('invalid token format')
    }
    const payload = JSON.parse(Buffer.from(payloadB64, 'base64url').toString())
    if (payload.exp && Date.now() > payload.exp) {
      // Token expired — redirect to login
      const loginUrl = new URL('/login', req.url)
      loginUrl.searchParams.set('redirect', pathname)
      return NextResponse.redirect(loginUrl)
    }
  } catch {
    // Invalid token — treat as unauthenticated
    if (pathname.startsWith('/api/')) {
      return NextResponse.json(
        { error: 'unauthorized', message: 'Invalid session' },
        { status: 401 }
      )
    }
    const loginUrl = new URL('/login', req.url)
    return NextResponse.redirect(loginUrl)
  }

  return NextResponse.next()
}

export const config = {
  matcher: [
    /*
     * Match all request paths except:
     * - _next/static, _next/image (static files)
     * - favicon.ico, icons, manifest (public assets)
     */
    '/((?!_next/static|_next/image|favicon.ico|icons|manifest.json|apple-touch-icon).*)',
  ],
}