import type { NextRequest } from 'next/server';
import { NextResponse } from 'next/server';

import createNextIntlMiddleware from 'next-intl/middleware';

import { isSuperAdmin } from '@kit/admin';
import { routing } from '@kit/i18n/routing';
import { getSafeRedirectPath } from '@kit/shared/utils';
import { checkRequiresMultiFactorAuthentication } from '@kit/supabase/check-requires-mfa';
import { createMiddlewareClient } from '@kit/supabase/middleware-client';

import pathsConfig from '~/config/paths.config';

const NEXT_ACTION_HEADER = 'next-action';

export const config = {
  matcher: ['/((?!_next/static|_next/image|images|locales|assets|api/*).*)'],
};

// create i18n middleware once at module scope
const handleI18nRouting = createNextIntlMiddleware(routing);

const getUser = (request: NextRequest, response: NextResponse) => {
  const supabase = createMiddlewareClient(request, response);

  return supabase.auth.getClaims();
};

export default async function proxy(request: NextRequest) {
  // run next-intl middleware first to get the i18n-aware response
  const response = handleI18nRouting(request);

  // apply secure headers on top of the i18n response
  const secureHeadersResponse = await createResponseWithSecureHeaders(response);

  // set a unique request ID for each request
  // this helps us log and trace requests
  setRequestId(request);

  // handle patterns for specific routes
  const handlePattern = await matchUrlPattern(request.url);

  // if a pattern handler exists, call it
  if (handlePattern) {
    const patternHandlerResponse = await handlePattern(
      request,
      secureHeadersResponse,
    );

    // if a pattern handler returns a response, return it
    if (patternHandlerResponse) {
      return patternHandlerResponse;
    }
  }

  // append the action path to the request headers
  // which is useful for knowing the action path in server actions
  if (isServerAction(request)) {
    secureHeadersResponse.headers.set(
      'x-action-path',
      request.nextUrl.pathname,
    );
  }

  // if no pattern handler returned a response,
  // return the session response
  return secureHeadersResponse;
}

function isServerAction(request: NextRequest) {
  const headers = new Headers(request.headers);

  return headers.has(NEXT_ACTION_HEADER);
}

async function adminMiddleware(request: NextRequest, response: NextResponse) {
  const isAdminPath = request.nextUrl.pathname.startsWith('/admin');

  if (!isAdminPath) {
    return;
  }

  const { data, error } = await getUser(request, response);

  // If user is not logged in, redirect to sign in page.
  // This should never happen, but just in case.
  if (!data?.claims || error) {
    return NextResponse.redirect(
      new URL(pathsConfig.auth.signIn, request.nextUrl.origin).href,
    );
  }

  const client = createMiddlewareClient(request, response);
  const userIsSuperAdmin = await isSuperAdmin(client);

  // If user is not an admin, redirect to 404 page.
  if (!userIsSuperAdmin) {
    return NextResponse.redirect(new URL('/404', request.nextUrl.origin).href);
  }

  // in all other cases, return the response
  return response;
}

/**
 * Define URL patterns and their corresponding handlers.
 */
async function getPatterns() {
  let URLPattern = globalThis.URLPattern;

  if (!URLPattern) {
    const { URLPattern: polyfill } = await import('urlpattern-polyfill');
    URLPattern = polyfill as typeof URLPattern;
  }

  return [
    {
      pattern: new URLPattern({ pathname: '/admin/*?' }),
      handler: adminMiddleware,
    },
    {
      pattern: new URLPattern({ pathname: '/auth/*?' }),
      handler: async (req: NextRequest, res: NextResponse) => {
        const { data } = await getUser(req, res);

        // the user is logged out, so we don't need to do anything
        if (!data?.claims) {
          return;
        }

        // check if we need to verify MFA (user is authenticated but needs to verify MFA)
        const isVerifyMfa = req.nextUrl.pathname === pathsConfig.auth.verifyMfa;

        // If user is logged in and does not need to verify MFA,
        // redirect to home page.
        if (!isVerifyMfa) {
          const nextPath = getSafeRedirectPath(
            req.nextUrl.searchParams.get('next'),
            pathsConfig.app.home,
          );

          return NextResponse.redirect(
            new URL(nextPath, req.nextUrl.origin).href,
          );
        }
      },
    },
    {
      pattern: new URLPattern({ pathname: '/home/*?' }),
      handler: async (req: NextRequest, res: NextResponse) => {
        const { data } = await getUser(req, res);
        const { origin, pathname: next } = req.nextUrl;

        // If user is not logged in, redirect to sign in page.
        if (!data?.claims) {
          const signIn = pathsConfig.auth.signIn;
          const redirectPath = `${signIn}?next=${next}`;

          return NextResponse.redirect(new URL(redirectPath, origin).href);
        }

        const supabase = createMiddlewareClient(req, res);

        const requiresMultiFactorAuthentication =
          await checkRequiresMultiFactorAuthentication(supabase);

        // If user requires multi-factor authentication, redirect to MFA page.
        if (requiresMultiFactorAuthentication) {
          return NextResponse.redirect(
            new URL(pathsConfig.auth.verifyMfa, origin).href,
          );
        }
      },
    },
  ];
}

/**
 * Match URL patterns to specific handlers.
 * @param url
 */
async function matchUrlPattern(url: string) {
  const patterns = await getPatterns();
  const input = url.split('?')[0];

  for (const pattern of patterns) {
    const patternResult = pattern.pattern.exec(input);

    if (patternResult !== null && 'pathname' in patternResult) {
      return pattern.handler;
    }
  }
}

/**
 * Set a unique request ID for each request.
 * @param request
 */
function setRequestId(request: Request) {
  request.headers.set('x-correlation-id', crypto.randomUUID());
}

/**
 * @name createResponseWithSecureHeaders
 * @description Create a middleware with enhanced headers applied (if applied).
 * This is disabled by default. To enable set ENABLE_STRICT_CSP=true
 */
async function createResponseWithSecureHeaders(response: NextResponse) {
  const enableStrictCsp = process.env.ENABLE_STRICT_CSP ?? 'false';

  // we disable ENABLE_STRICT_CSP by default
  if (enableStrictCsp === 'false') {
    return response;
  }

  const { createCspResponse } = await import('./lib/create-csp-response');
  const cspResponse = await createCspResponse();

  // set the CSP headers on the i18n response
  if (cspResponse) {
    for (const [key, value] of cspResponse.headers.entries()) {
      response.headers.set(key, value);
    }
  }

  return response;
}