const etag = require("etag");
const cheerio = require("cheerio");

const getContentTypeHeader = require("../utils/getContentTypeHeader");
const rewriteBareModuleIdentifiers = require("../utils/rewriteBareModuleIdentifiers");

function serveHTMLModule(req, res) {
  try {
    const $ = cheerio.load(req.entry.content.toString("utf8"));

    $("script[type=module]").each((index, element) => {
      $(element).html(
        rewriteBareModuleIdentifiers($(element).html(), req.packageConfig)
      );
    });

    const code = $.html();

    res
      .set({
        "Content-Length": Buffer.byteLength(code),
        "Content-Type": getContentTypeHeader(req.entry.contentType),
        "Cache-Control": "public, max-age=31536000, immutable", // 1 year
        ETag: etag(code),
        "Cache-Tag": "file, html-file, html-module"
      })
      .send(code);
  } catch (error) {
    console.error(error);

    const errorName = error.constructor.name;
    const errorMessage = error.message.replace(
      /^.*?\/unpkg-.+?\//,
      `/${req.packageSpec}/`
    );
    const codeFrame = error.codeFrame;
    const debugInfo = `${errorName}: ${errorMessage}\n\n${codeFrame}`;

    res
      .status(500)
      .type("text")
      .send(
        `Cannot generate module for ${req.packageSpec}${
          req.filename
        }\n\n${debugInfo}`
      );
  }
}

module.exports = serveHTMLModule;