file.js

// A module handling file upload, file fields, and file scripting.

const urllib = require('url');

const _ = require('lodash');
const fetch = require('node-fetch');

const markFileFieldsInBundle = (bundle, inputFields) => {
  const fileFieldKeys = inputFields
    .filter((field) => field.type === 'file')
    .map((field) => field.key);

  if (fileFieldKeys.length > 0) {
    // Add it to bundle so that functions that don't have access to app
    // definition, such as bundleConverter, knows which fields are files
    bundle._fileFieldKeys = fileFieldKeys;
  }
};

const hasFileFields = (bundle) => {
  return bundle._fileFieldKeys && bundle._fileFieldKeys.length > 0;
};

const isFileField = (fieldKey, bundle) => {
  if (!bundle._fileFieldKeys) {
    return false;
  }
  return bundle._fileFieldKeys.indexOf(fieldKey) >= 0;
};

const isAnyFileFieldSet = (bundle) => {
  const body = _.get(bundle, 'request.body');
  if (body && bundle._fileFieldKeys) {
    for (const k of bundle._fileFieldKeys) {
      if (body[k]) {
        return true;
      }
    }
  }
  return false;
};

const isUrl = (str) => {
  try {
    const parsed = new urllib.URL(str);
    return (
      (parsed.protocol === 'http:' || parsed.protocol === 'https:') &&
      parsed.hostname
    );
  } catch (e) {
    return false;
  }
};

const extractFilenameFromContent = (content) =>
  content.substr(0, 12).replace('.txt', '') + ' ... .txt';

const extractFilenameFromContentDisposition = (value) => {
  let filename = '';

  // Follows RFC 6266
  const patterns = [
    // Example: "attachment; filename*= UTF-8''%e2%82%ac%20rates"
    /filename\*\s*=\s*[a-z0-9_-]+''(.*)(?:;|$)/gi,

    // Example: 'INLINE; FILENAME= "an example.html"'
    /filename\s*=\s*"([^"]+)"/gi,

    // Example: 'Attachment; filename=example.html'
    /filename\s*=\s*([^ ]+)/gi,
  ];

  for (const pattern of patterns) {
    const match = pattern.exec(value);
    if (match) {
      filename = match[1];
      break;
    }
  }

  if (filename) {
    filename = decodeURIComponent(filename);
  }

  return filename;
};

const extractFilenameFromUrl = (url) => {
  const pathname = new urllib.URL(url).pathname;
  if (pathname) {
    const parts = pathname.split('/');
    return parts[parts.length - 1] || '';
  }
  return '';
};

const downloadFile = async (url) => {
  const response = await fetch(url);
  if (!response.ok) {
    throw new Error(`Got ${response.statusText} when download file: ${url}`);
  }

  const disposition = response.headers.get('content-disposition');
  const filename = disposition
    ? extractFilenameFromContentDisposition(disposition)
    : extractFilenameFromUrl(response.url);
  const contentType =
    response.headers.get('content-type') || 'application/octet-stream';

  const buffer = await response.buffer();

  return {
    meta: { filename, contentType },
    content: buffer,
  };
};

const ContentBackedLazyFile = (content, fileMeta) => {
  const meta = async () => {
    return {
      filename: fileMeta.filename || extractFilenameFromContent(content),
      contentType: fileMeta.contentType || 'text/plain',
    };
  };

  // readStream is only used by FormData.append(). And FormData.append(key,
  // data, options) accepts a string for its `data` argument, so instead of
  // trying to make the string a readable stream, we can just return the
  // string here.
  const readStream = async () => content;

  return { meta, readStream };
};

const UrlBackedLazyFile = (url, fileMeta) => {
  const hasCompleteMeta = fileMeta.filename && fileMeta.contentType;

  let cachedFile;
  const downloadFileWithCache = async (fileUrl) => {
    // Cache file so when we call LazyFile.meta or LazyFile.readStream, we
    // don't need to send an HTTP request again
    if (cachedFile) {
      return cachedFile;
    }

    const file = await downloadFile(fileUrl);
    cachedFile = file;
    return file;
  };

  const meta = async () => {
    if (hasCompleteMeta) {
      return fileMeta;
    }
    const file = await downloadFileWithCache(url);
    return _.extend(file.meta, fileMeta);
  };

  const readStream = async () => {
    const file = await downloadFileWithCache(url);
    return file.content;
  };

  return { meta, readStream };
};

const LazyFile = (urlOrContent, fileMeta, options) => {
  fileMeta = fileMeta || {};
  options = options || {};

  if (options.dontLoadUrl || !isUrl(urlOrContent)) {
    return ContentBackedLazyFile(urlOrContent, fileMeta);
  }
  return UrlBackedLazyFile(urlOrContent, fileMeta);
};

module.exports = {
  markFileFieldsInBundle,
  hasFileFields,
  isFileField,
  isAnyFileFieldSet,
  LazyFile,
};