middleware.ts

import { NextResponse } from "next/server"
import type { NextRequest } from "next/server"
import { match } from "@formatjs/intl-localematcher"
import Negotiator from "negotiator"

import type { Locale, Theme } from "@/utils/constants"
import {
  COOKIE_MAX_AGE,
  DEFAULT_LOCALE,
  DEFAULT_THEME,
  LOCALES,
  THEMES,
} from "@/utils/constants"

export const middleware = (request: NextRequest): NextResponse => {
  const response = NextResponse.next()

  let locale = request.cookies.get("locale")?.value
  if (locale == null || !LOCALES.includes(locale as Locale)) {
    try {
      const headers = {
        "accept-language":
          request.headers.get("accept-language") ?? DEFAULT_LOCALE,
      }
      const languages = new Negotiator({ headers }).languages()
      locale = match(languages, LOCALES.slice(), DEFAULT_LOCALE)
    } catch {
      locale = DEFAULT_LOCALE
    }
    response.cookies.set("locale", locale, {
      path: "/",
      maxAge: COOKIE_MAX_AGE,
    })
  }

  const theme = request.cookies.get("theme")?.value
  if (theme == null || !THEMES.includes(theme as Theme)) {
    response.cookies.set("theme", DEFAULT_THEME, {
      path: "/",
      maxAge: COOKIE_MAX_AGE,
    })
  }

  return response
}

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