const validateNpmPackageName = require("validate-npm-package-name");
const parsePackageURL = require("../utils/parsePackageURL");
const createSearch = require("./utils/createSearch");

const KnownQueryParams = {
  main: true,
  meta: true,
  module: true
};

function isKnownQueryParam(param) {
  return !!KnownQueryParams[param];
}

function queryIsKnown(query) {
  return Object.keys(query).every(isKnownQueryParam);
}

function sanitizeQuery(query) {
  const saneQuery = {};

  Object.keys(query).forEach(param => {
    if (isKnownQueryParam(param)) saneQuery[param] = query[param];
  });

  return saneQuery;
}

/**
 * Parse and validate the URL.
 */
function parseURL(req, res, next) {
  // Redirect /_meta/path to /path?meta.
  if (req.path.match(/^\/_meta\//)) {
    req.query.meta = "";
    return res.redirect(302, req.path.substr(6) + createSearch(req.query));
  }

  // Redirect /path?json => /path?meta
  if (req.query.json != null) {
    delete req.query.json;
    req.query.meta = "";
    return res.redirect(302, req.path + createSearch(req.query));
  }

  // Redirect requests with unknown query params to their equivalents
  // with only known params so they can be served from the cache. This
  // prevents people using random query params designed to bust the cache.
  if (!queryIsKnown(req.query)) {
    return res.redirect(302, req.path + createSearch(sanitizeQuery(req.query)));
  }

  const url = parsePackageURL(req.url);

  // Disallow invalid URLs.
  if (url == null) {
    return res
      .status(403)
      .type("text")
      .send(`Invalid URL: ${req.url}`);
  }

  const nameErrors = validateNpmPackageName(url.packageName).errors;

  // Disallow invalid package names.
  if (nameErrors) {
    const reason = nameErrors.join(", ");
    return res
      .status(403)
      .type("text")
      .send(`Invalid package name "${url.packageName}" (${reason})`);
  }

  req.packageName = url.packageName;
  req.packageVersion = url.packageVersion;
  req.packageSpec = `${url.packageName}@${url.packageVersion}`;
  req.pathname = url.pathname;
  req.filename = url.filename;
  req.search = url.search;
  req.query = url.query;

  next();
}

module.exports = parseURL;