lambda-api/lib/response.js

Lightweight web framework for your serverless applications

'use strict';
/**
 * Lightweight web framework for your serverless applications
 * @author Jeremy Daly <jeremy@jeremydaly.com>
 * @license MIT
 */

const UTILS = require('./utils.js');

const fs = require('fs'); // Require Node.js file system
const path = require('path'); // Require Node.js path
const compression = require('./compression'); // Require compression lib
const { ResponseError, FileError, ApiError } = require('./errors'); // Require custom errors

// Lazy load AWS S3 service
const S3 = () => require('./s3-service');

class RESPONSE {
  // Create the constructor function.
  constructor(app, request) {
    // Add a reference to the main app
    app._response = this;

    // Create a reference to the app
    this.app = app;

    // Create a reference to the request
    this._request = request;

    // Create a reference to the JSON serializer
    this._serializer = app._serializer;

    // Set the default state to processing
    this._state = 'processing';

    // Default statusCode to 200
    this._statusCode = 200;

    // Default the header
    this._headers = Object.assign(
      {
        // Set the Content-Type by default
        'content-type': ['application/json'], //charset=UTF-8
      },
      app._headers
    );

    // base64 encoding flag
    this._isBase64 = app._isBase64;

    // compression flag
    this._compression = app._compression;

    // Default callback function
    this._callback = 'callback';

    // Default Etag support
    this._etag = false;

    // Default response object
    this._response = {};
  }

  // Sets the statusCode
  status(code) {
    this._statusCode = code;
    return this;
  }

  // Adds a header field
  header(key, value, append) {
    let _key = key.toLowerCase(); // store as lowercase
    let _values = value ? (Array.isArray(value) ? value : [value]) : [''];
    this._headers[_key] = append
      ? this.hasHeader(_key)
        ? this._headers[_key].concat(_values)
        : _values
      : _values;
    return this;
  }

  // Gets a header field
  getHeader(key, asArr) {
    if (!key)
      return asArr
        ? this._headers
        : Object.keys(this._headers).reduce(
            (headers, key) =>
              Object.assign(headers, { [key]: this._headers[key].toString() }),
            {}
          ); // return all headers
    return asArr
      ? this._headers[key.toLowerCase()]
      : this._headers[key.toLowerCase()]
      ? this._headers[key.toLowerCase()].toString()
      : undefined;
  }

  // Issue #130
  setHeader(...args) {
    return this.header(...args);
  }

  getHeaders() {
    return this._headers;
  }

  // Removes a header field
  removeHeader(key) {
    delete this._headers[key.toLowerCase()];
    return this;
  }

  // Returns boolean if header exists
  hasHeader(key) {
    return this.getHeader(key ? key : '') !== undefined;
  }

  // Convenience method for JSON
  json(body) {
    this.header('Content-Type', 'application/json').send(
      this._serializer(body)
    );
  }

  // Convenience method for JSONP
  jsonp(body) {
    // Check the querystring for callback or cb
    let query = this.app._event.queryStringParameters || {};
    let cb = query[this.app._callbackName];

    this.header('Content-Type', 'application/json').send(
      (cb ? cb.replace(' ', '_') : 'callback') +
        '(' +
        this._serializer(body) +
        ')'
    );
  }

  // Convenience method for HTML
  html(body) {
    this.header('Content-Type', 'text/html').send(body);
  }

  // Convenience method for setting Location header
  location(path) {
    this.header('Location', UTILS.encodeUrl(path));
    return this;
  }

  // Convenience method for Redirect
  async redirect(path) {
    let statusCode = 302; // default

    try {
      // If status code is provided
      if (arguments.length === 2) {
        if ([300, 301, 302, 303, 307, 308].includes(arguments[0])) {
          statusCode = arguments[0];
          path = arguments[1];
        } else {
          throw new ResponseError(
            arguments[0] + ' is an invalid redirect status code',
            arguments[0]
          );
        }
      }

      // Auto convert S3 paths to signed URLs
      if (UTILS.isS3(path)) path = await this.getLink(path);

      let url = UTILS.escapeHtml(path);

      this.location(path)
        .status(statusCode)
        .html(
          `<p>${statusCode} Redirecting to <a href="${url}">${url}</a></p>`
        );
    } catch (e) {
      this.error(e);
    }
  } // end redirect

  // Convenience method for retrieving a signed link to an S3 bucket object
  async getLink(path, expires, callback) {
    let params = UTILS.parseS3(path);

    // Default Expires
    params.Expires = !isNaN(expires) ? parseInt(expires) : 900;

    // Default callback
    let fn =
      typeof expires === 'function'
        ? expires
        : typeof callback === 'function'
        ? callback
        : (e) => {
            if (e) this.error(e);
          };

    // getSignedUrl doesn't support .promise()
    return await new Promise((r) =>
      S3().getSignedUrl('getObject', params, async (e, url) => {
        if (e) {
          // Execute callback with caught error
          await fn(e);
          this.error(e); // Throw error if not done in callback
        }
        r(url); // return the url
      })
    );
  } // end getLink

  // Convenience method for setting cookies
  // see https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie
  cookie(name, value, opts = {}) {
    // Set the name and value of the cookie
    let cookieString =
      (typeof name !== 'string' ? name.toString() : name) +
      '=' +
      encodeURIComponent(UTILS.encodeBody(value));

    // domain (String): Domain name for the cookie
    cookieString += opts.domain ? '; Domain=' + opts.domain : '';

    // expires (Date): Expiry date of the cookie, convert to GMT
    cookieString +=
      opts.expires && typeof opts.expires.toUTCString === 'function'
        ? '; Expires=' + opts.expires.toUTCString()
        : '';

    // httpOnly (Boolean): Flags the cookie to be accessible only by the web server
    cookieString += opts.httpOnly && opts.httpOnly === true ? '; HttpOnly' : '';

    // maxAge (Number) Set expiry time relative to the current time in milliseconds
    cookieString +=
      opts.maxAge && !isNaN(opts.maxAge)
        ? '; MaxAge=' +
          ((opts.maxAge / 1000) | 0) +
          (!opts.expires
            ? '; Expires=' + new Date(Date.now() + opts.maxAge).toUTCString()
            : '')
        : '';

    // path (String): Path for the cookie
    cookieString += opts.path ? '; Path=' + opts.path : '; Path=/';

    // secure (Boolean): Marks the cookie to be used with HTTPS only
    cookieString += opts.secure && opts.secure === true ? '; Secure' : '';

    // sameSite (Boolean or String) Value of the "SameSite" Set-Cookie attribute
    // see https://tools.ietf.org/html/draft-ietf-httpbis-cookie-same-site-00#section-4.1.1.
    cookieString +=
      opts.sameSite !== undefined
        ? '; SameSite=' +
          (opts.sameSite === true
            ? 'Strict'
            : opts.sameSite === false
            ? 'Lax'
            : opts.sameSite)
        : '';

    this.header('Set-Cookie', cookieString, true);
    return this;
  }

  // Convenience method for clearing cookies
  clearCookie(name, opts = {}) {
    let options = Object.assign(opts, { expires: new Date(1), maxAge: -1000 });
    return this.cookie(name, '', options);
  }

  // Set content-disposition header and content type
  attachment(filename) {
    // Check for supplied filename/path
    let name =
      typeof filename === 'string' && filename.trim().length > 0
        ? path.parse(filename)
        : undefined;
    this.header(
      'Content-Disposition',
      'attachment' + (name ? '; filename="' + name.base + '"' : '')
    );

    // If name exits, attempt to set the type
    if (name) {
      this.type(name.ext);
    }
    return this;
  }

  // Convenience method combining attachment() and sendFile()
  download(file, filename, options, callback) {
    let name = filename;
    let opts = typeof options === 'object' ? options : {};
    let fn = typeof callback === 'function' ? callback : undefined;

    // Add optional parameter support for callback
    if (typeof filename === 'function') {
      name = undefined;
      fn = filename;
    } else if (typeof options === 'function') {
      fn = options;
    }

    // Add optional parameter support for options
    if (typeof filename === 'object') {
      name = undefined;
      opts = filename;
    }

    // Add the Content-Disposition header
    this.attachment(
      name ? name : typeof file === 'string' ? path.basename(file) : null
    );

    // Send the file
    this.sendFile(file, opts, fn);
  }

  // Convenience method for returning static files
  async sendFile(file, options, callback) {
    let buffer, modified;

    let opts = typeof options === 'object' ? options : {};
    let fn = typeof callback === 'function' ? callback : () => {};

    // Add optional parameter support
    if (typeof options === 'function') {
      fn = options;
    }

    // Begin a try-catch block for callback errors
    try {
      // Create buffer based on input
      if (typeof file === 'string') {
        let filepath = file.trim();

        // If an S3 file identifier
        if (/^s3:\/\//i.test(filepath)) {
          let params = UTILS.parseS3(filepath);

          // Attempt to get the object from S3
          let data = await S3().getObject(params).promise();

          // Set results, type and header
          buffer = data.Body;
          modified = data.LastModified;
          this.type(data.ContentType);
          this.header('ETag', data.ETag);

          // else try and load the file locally
        } else {
          buffer = fs.readFileSync((opts.root ? opts.root : '') + filepath);
          modified =
            opts.lastModified !== false
              ? fs.statSync((opts.root ? opts.root : '') + filepath).mtime
              : undefined;
          this.type(path.extname(filepath));
        }
        // If the input is a buffer, pass through
      } else if (Buffer.isBuffer(file)) {
        buffer = file;
      } else {
        throw new FileError('Invalid file', { path: file });
      }

      // Add headers from options
      if (typeof opts.headers === 'object') {
        Object.keys(opts.headers).map((header) => {
          this.header(header, opts.headers[header]);
        });
      }

      // Add cache-control headers
      if (opts.cacheControl !== false) {
        if (opts.cacheControl !== true && opts.cacheControl !== undefined) {
          this.cache(opts.cacheControl);
        } else {
          this.cache(!isNaN(opts.maxAge) ? opts.maxAge : 0, opts.private);
        }
      }

      // Add last-modified headers
      if (opts.lastModified !== false) {
        this.modified(opts.lastModified ? opts.lastModified : modified);
      }

      // Execute callback
      await fn();

      // Set base64 encoding flag
      this._isBase64 = true;
      // Convert buffer to base64 string
      this.send(buffer.toString('base64'));
    } catch (e) {
      // TODO: Add second catch?
      // Execute callback with caught error
      await fn(e);

      // If missing file
      if (e.code === 'ENOENT') {
        this.error(new FileError('No such file', e));
      } else {
        this.error(e); // Throw error if not done in callback
      }
    }
  } // end sendFile

  // Convenience method for setting type
  type(type) {
    let mimeType = UTILS.mimeLookup(type, this.app._mimeTypes);
    if (mimeType) {
      this.header('Content-Type', mimeType);
    }
    return this;
  }

  // Convenience method for sending status codes
  sendStatus(status) {
    this.status(status).send(UTILS.statusLookup(status));
  }

  // Convenience method for setting CORS headers
  cors(options) {
    const opts = typeof options === 'object' ? options : {};

    // Check for existing headers
    let acao = this.getHeader('Access-Control-Allow-Origin');
    let acam = this.getHeader('Access-Control-Allow-Methods');
    let acah = this.getHeader('Access-Control-Allow-Headers');

    // Default CORS headers
    this.header(
      'Access-Control-Allow-Origin',
      opts.origin ? opts.origin : acao ? acao : '*'
    );
    this.header(
      'Access-Control-Allow-Methods',
      opts.methods
        ? opts.methods
        : acam
        ? acam
        : 'GET, PUT, POST, DELETE, OPTIONS'
    );
    this.header(
      'Access-Control-Allow-Headers',
      opts.headers
        ? opts.headers
        : acah
        ? acah
        : 'Content-Type, Authorization, Content-Length, X-Requested-With'
    );

    // Optional CORS headers
    if (opts.maxAge && !isNaN(opts.maxAge))
      this.header(
        'Access-Control-Max-Age',
        ((opts.maxAge / 1000) | 0).toString()
      );
    if (opts.credentials)
      this.header(
        'Access-Control-Allow-Credentials',
        opts.credentials.toString()
      );
    if (opts.exposeHeaders)
      this.header('Access-Control-Expose-Headers', opts.exposeHeaders);

    return this;
  }

  // Enable/Disable Etag
  etag(enable) {
    this._etag = enable === true ? true : false;
    return this;
  }

  // Add cache-control headers
  cache(maxAge, isPrivate = false) {
    // if custom string value
    if (maxAge !== true && maxAge !== undefined && typeof maxAge === 'string') {
      this.header('Cache-Control', maxAge);
    } else if (maxAge === false) {
      this.header('Cache-Control', 'no-cache, no-store, must-revalidate');
    } else {
      maxAge = maxAge && !isNaN(maxAge) ? (maxAge / 1000) | 0 : 0;
      this.header(
        'Cache-Control',
        (isPrivate === true ? 'private, ' : '') + 'max-age=' + maxAge
      );
      this.header('Expires', new Date(Date.now() + maxAge).toUTCString());
    }
    return this;
  }

  // Add last-modified headers
  modified(date) {
    if (date !== false) {
      let lastModified =
        date && typeof date.toUTCString === 'function'
          ? date
          : date && Date.parse(date)
          ? new Date(date)
          : new Date();
      this.header('Last-Modified', lastModified.toUTCString());
    }
    return this;
  }

  // Sends the request to the main callback
  send(body) {
    // Generate Etag
    if (
      this._etag && // if etag support enabled
      ['GET', 'HEAD'].includes(this._request.method) &&
      !this.hasHeader('etag') &&
      this._statusCode === 200
    ) {
      this.header('etag', '"' + UTILS.generateEtag(body) + '"');
    }

    // Check for matching Etag
    if (
      this._request.headers['if-none-match'] &&
      this._request.headers['if-none-match'] === this.getHeader('etag')
    ) {
      this.status(304);
      body = '';
    }

    let headers = {};
    let cookies = {};

    if (this._request.payloadVersion === '2.0') {
      if (this._headers['set-cookie']) {
        cookies = { cookies: this._headers['set-cookie'] };
        delete this._headers['set-cookie'];
      }
    }

    if (this._request._multiValueSupport) {
      headers = { multiValueHeaders: this._headers };
    } else {
      headers = { headers: UTILS.stringifyHeaders(this._headers) };
    }

    // Create the response
    this._response = Object.assign(
      {},
      headers,
      cookies,
      {
        statusCode: this._statusCode,
        body:
          this._request.method === 'HEAD'
            ? ''
            : UTILS.encodeBody(body, this._serializer),
        isBase64Encoded: this._isBase64,
      },
      this._request.interface === 'alb'
        ? {
            statusDescription: `${this._statusCode} ${UTILS.statusLookup(
              this._statusCode
            )}`,
          }
        : {}
    );

    // Compress the body
    if (this._compression && this._response.body) {
      const { data, contentEncoding } = compression.compress(
        this._response.body,
        this._request.headers,
        Array.isArray(this._compression) ? this._compression : null
      );
      if (contentEncoding) {
        Object.assign(this._response, {
          body: data.toString('base64'),
          isBase64Encoded: true,
        });
        if (this._response.multiValueHeaders) {
          this._response.multiValueHeaders['content-encoding'] = [
            contentEncoding,
          ];
        } else {
          this._response.headers['content-encoding'] = contentEncoding;
        }
      }
    }

    // Trigger the callback function
    this.app._callback(null, this._response, this);
  } // end send

  // Trigger API error
  error(code, e, detail) {
    const message = typeof code !== 'number' ? code : e;
    const statusCode = typeof code === 'number' ? code : undefined;
    const errorDetail =
      typeof code !== 'number' && e !== undefined ? e : detail;

    const errorToSend =
      typeof message === 'string'
        ? new ApiError(message, statusCode, errorDetail)
        : message;

    this.app.catchErrors(errorToSend, this, statusCode, errorDetail);
  } // end error
} // end Response class

// Export the response object
module.exports = RESPONSE;