unpkg/server/actions/serveFile.js

const fs = require("fs");
const path = require("path");
const etag = require("etag");
const babel = require("babel-core");

const IndexPage = require("../components/IndexPage");
const renderPage = require("../utils/renderPage");
const getMetadata = require("../utils/getMetadata");
const getFileContentType = require("../utils/getFileContentType");
const unpkgRewrite = require("../utils/unpkgRewriteBabelPlugin");
const getEntries = require("../utils/getEntries");

/**
 * Automatically generate HTML pages that show package contents.
 */
const AutoIndex = !process.env.DISABLE_INDEX;

/**
 * Maximum recursion depth for meta listings.
 */
const MaximumDepth = 128;

function rewriteBareModuleIdentifiers(file, packageConfig, callback) {
  const dependencies = Object.assign(
    {},
    packageConfig.peerDependencies,
    packageConfig.dependencies
  );

  const options = {
    // Ignore .babelrc and package.json babel config
    // because we haven't installed dependencies so
    // we can't load plugins; see #84
    babelrc: false,
    plugins: [unpkgRewrite(dependencies)]
  };

  babel.transformFile(file, options, (error, result) => {
    callback(error, result && result.code);
  });
}

/**
 * Send the file, JSON metadata, or HTML directory listing.
 */
function serveFile(req, res) {
  if (req.query.meta != null) {
    // Serve JSON metadata.
    getMetadata(
      req.packageDir,
      req.filename,
      req.stats,
      MaximumDepth,
      (error, metadata) => {
        if (error) {
          console.error(error);

          res
            .status(500)
            .type("text")
            .send(
              `Cannot generate metadata for ${req.packageSpec}${req.filename}`
            );
        } else {
          // Cache metadata for 1 year.
          res
            .set({
              "Cache-Control": "public, max-age=31536000",
              "Cache-Tag": "meta"
            })
            .send(metadata);
        }
      }
    );
  } else if (req.stats.isFile()) {
    // Serve a file.
    const file = path.join(req.packageDir, req.filename);

    let contentType = getFileContentType(file);

    if (contentType === "text/html") contentType = "text/plain"; // We can't serve HTML because bad people :(

    if (contentType === "application/javascript" && req.query.module != null) {
      // Serve a JavaScript module.
      rewriteBareModuleIdentifiers(file, req.packageConfig, (error, code) => {
        if (error) {
          console.error(error);

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

          res
            .status(500)
            .type("text")
            .send(
              `Cannot generate module for ${req.packageSpec}${
                req.filename
              }\n\n${debugInfo}`
            );
        } else {
          // Cache modules for 1 year.
          res
            .set({
              "Content-Type": `${contentType}; charset=utf-8`,
              "Content-Length": Buffer.byteLength(code),
              "Cache-Control": "public, max-age=31536000",
              "Cache-Tag": "file,js-file,js-module"
            })
            .send(code);
        }
      });
    } else {
      // Serve some other static file.
      const tags = ["file"];

      const ext = path.extname(req.filename).substr(1);
      if (ext) {
        tags.push(`${ext}-file`);
      }

      if (contentType === "application/javascript") {
        contentType += "; charset=utf-8";
      }

      // Cache files for 1 year.
      res.set({
        "Content-Type": contentType,
        "Content-Length": req.stats.size,
        "Cache-Control": "public, max-age=31536000",
        "Last-Modified": req.stats.mtime.toUTCString(),
        ETag: etag(req.stats),
        "Cache-Tag": tags.join(",")
      });

      const stream = fs.createReadStream(file);

      stream.on("error", error => {
        console.error(`Cannot send file ${req.packageSpec}${req.filename}`);
        console.error(error);
        res.sendStatus(500);
      });

      stream.pipe(res);
    }
  } else if (AutoIndex && req.stats.isDirectory()) {
    // Serve an HTML directory listing.
    getEntries(path.join(req.packageDir, req.filename)).then(
      entries => {
        const html = renderPage(IndexPage, {
          packageInfo: req.packageInfo,
          version: req.packageVersion,
          dir: req.filename,
          entries
        });

        // Cache HTML directory listings for 1 minute.
        res
          .set({
            "Cache-Control": "public, max-age=60",
            "Cache-Tag": "index"
          })
          .send(html);
      },
      error => {
        console.error(error);

        res
          .status(500)
          .type("text")
          .send(`Cannot read entries for ${req.packageSpec}${req.filename}`);
      }
    );
  } else {
    res
      .status(403)
      .type("text")
      .send(`Cannot serve ${req.packageSpec}${req.filename}; it's not a file`);
  }
}

module.exports = serveFile;