getNetlifyRoutes.js

// Adapted from @sls-next/lambda-at-edge (v1.2.0-alpha.3)
// See: https://github.com/danielcondemarin/serverless-next.js/blob/57142970b08e6bc3faf0fc70749b3b0501ad7869/packages/lambda-at-edge/src/lib/expressifyDynamicRoute.ts#L4

const {
  CATCH_ALL_REGEX,
  OPTIONAL_CATCH_ALL_REGEX,
  DYNAMIC_PARAMETER_REGEX,
} = require("../constants/regex");

// Convert dynamic NextJS routes into their Netlify-equivalent
// Note that file endings (.json) must be removed for catch-all and optional
// catch-all routes to work. That's why the regexes defined above include
// the (.json)? option
const getNetlifyRoutes = (nextRoute) => {
  let netlifyRoutes = [nextRoute];

  // If the route is an optional catch-all route, we need to add a second
  // Netlify route for the base path (when no parameters are present).
  // The file ending must be present!
  if (nextRoute.match(OPTIONAL_CATCH_ALL_REGEX)) {
    let netlifyRoute = nextRoute.replace(OPTIONAL_CATCH_ALL_REGEX, "$2");

    // When optional catch-all route is at top-level, the regex on line 19 will
    // create an empty string, but actually needs to be a forward slash
    if (netlifyRoute === "") netlifyRoute = "/";

    // When optional catch-all route is at top-level, the regex on line 19 will
    // create an incorrect route for the data route. For example, it creates
    // /_next/data/%BUILDID%.json, but NextJS looks for
    // /_next/data/%BUILDID%/index.json
    netlifyRoute = netlifyRoute.replace(
      /(\/_next\/data\/[^/]+).json/,
      "$1/index.json"
    );

    // Add second route to the front of the array
    netlifyRoutes.unshift(netlifyRoute);
  }

  // Replace catch-all, e.g., [...slug]
  netlifyRoutes = netlifyRoutes.map((route) =>
    route.replace(CATCH_ALL_REGEX, "/:$1/*")
  );

  // Replace optional catch-all, e.g., [[...slug]]
  netlifyRoutes = netlifyRoutes.map((route) =>
    route.replace(OPTIONAL_CATCH_ALL_REGEX, "/*")
  );

  // Replace dynamic parameters, e.g., [id]
  netlifyRoutes = netlifyRoutes.map((route) =>
    route.replace(DYNAMIC_PARAMETER_REGEX, "/:$1")
  );

  return netlifyRoutes;
};

module.exports = getNetlifyRoutes;