// src/middleware.ts
// Next.js Middleware for locale detection and routing

import { NextRequest, NextResponse } from 'next/server'
import { locales, defaultLocale, isValidLocale, type Locale } from '@/lib/i18n'

// Paths that should not be affected by locale routing
const PUBLIC_FILE = /\.(.*)$/
const EXCLUDED_PATHS = ['/admin', '/api', '/_next', '/favicon.ico', '/robots.txt', '/sitemap.xml']

/**
 * Detect user's preferred locale from Accept-Language header
 */
function getPreferredLocale(request: NextRequest): Locale {
  const acceptLanguage = request.headers.get('accept-language')

  if (!acceptLanguage) {
    return defaultLocale
  }

  // Parse Accept-Language header
  const languages = acceptLanguage
    .split(',')
    .map((lang) => {
      const [code, priority] = lang.trim().split(';q=')
      return {
        code: code.split('-')[0].toLowerCase(), // Get primary language code
        priority: priority ? parseFloat(priority) : 1,
      }
    })
    .sort((a, b) => b.priority - a.priority)

  // Find first matching locale
  for (const { code } of languages) {
    if (isValidLocale(code)) {
      return code
    }
  }

  return defaultLocale
}

/**
 * Get locale from cookie
 */
function getLocaleFromCookie(request: NextRequest): Locale | null {
  const cookieLocale = request.cookies.get('NEXT_LOCALE')?.value

  if (cookieLocale && isValidLocale(cookieLocale)) {
    return cookieLocale
  }

  return null
}

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

  // Skip locale routing for excluded paths and public files
  if (
    EXCLUDED_PATHS.some((path) => pathname.startsWith(path)) ||
    PUBLIC_FILE.test(pathname)
  ) {
    return NextResponse.next()
  }

  // Check if pathname already has a valid locale prefix
  const pathnameLocale = pathname.split('/')[1]

  if (isValidLocale(pathnameLocale)) {
    // Valid locale in URL, set cookie and continue
    const response = NextResponse.next()
    response.cookies.set('NEXT_LOCALE', pathnameLocale, {
      maxAge: 60 * 60 * 24 * 365, // 1 year
      path: '/',
    })
    return response
  }

  // No locale in URL, redirect to preferred locale
  const cookieLocale = getLocaleFromCookie(request)
  const preferredLocale = cookieLocale || getPreferredLocale(request)

  // Build new URL with locale prefix
  const newUrl = new URL(request.url)
  newUrl.pathname = `/${preferredLocale}${pathname === '/' ? '' : pathname}`

  // Redirect to localized URL
  const response = NextResponse.redirect(newUrl)
  response.cookies.set('NEXT_LOCALE', preferredLocale, {
    maxAge: 60 * 60 * 24 * 365, // 1 year
    path: '/',
  })

  return response
}

export const config = {
  // Match all paths except static files and API routes
  matcher: ['/((?!api|_next/static|_next/image|admin|favicon.ico).*)'],
}