middleware.ts

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

import { DEFAULT_TENANT_ID, getSubdomainFromHost, isValidTenantId } from './lib/makeswift/tenants'

export function middleware(request: NextRequest) {
  const host = request.headers.get('host') ?? ''
  const url = request.nextUrl.clone()

  // 1. Prefer the subdomain. This is how the Visual Builder connects, because a
  //    Makeswift host URL cannot contain a path (it is an origin only). The
  //    builder loads e.g. "siteA.localhost:3000", and we resolve the tenant
  //    from that subdomain.
  const subdomain = getSubdomainFromHost(host)
  if (subdomain != null && isValidTenantId(subdomain)) {
    // Avoid double-prefixing when the path already starts with the tenant
    // (e.g. a hand-typed "siteA.localhost:3000/siteA").
    if (url.pathname !== `/${subdomain}` && !url.pathname.startsWith(`/${subdomain}/`)) {
      url.pathname = `/${subdomain}${url.pathname}`
    }
    return NextResponse.rewrite(url)
  }

  // 2. Fall back to path-based routing for public viewing: if the first path
  //    segment is already a valid tenant (e.g. "/siteA/products"), let it
  //    through unchanged so the catch-all route reads the tenant from there.
  const firstPathSegment = url.pathname.split('/').at(1) ?? null
  if (firstPathSegment != null && isValidTenantId(firstPathSegment)) {
    return NextResponse.next()
  }

  // 3. No tenant in the host or the path -> default tenant.
  url.pathname = `/${DEFAULT_TENANT_ID}${url.pathname}`
  return NextResponse.rewrite(url)
}

export const config = {
  matcher: [
    /*
     * Match all request paths except for the ones starting with:
     * - _next/static (static files)
     * - _next/image (image optimization files)
     * - favicon.ico (favicon file)
     */
    '/((?!api|_next/static|_next/image|favicon.ico).*)',
  ],
}