wrapper.js

'use strict';
let rfr = require('rfr');
let LambdaError = rfr('errors');

/**
 * Wrap a module.exports clause to handle common Lambda handler for statusCode, errors, and body.
 * TODO: Add validation based on the swagger method.
 */


function wrapHeaders(res) {
  if (typeof res !== 'object') {
    console.error('Response is not an object', res);
    return res;
  }
  res.headers = {
    'Access-Control-Allow-Origin': '*'
  };
  return res;
}

function wrapFunction(func) {
  return (event, context, callback) => {
    try {
      func(event).then((data) => {
        callback(null, wrapHeaders({
          statusCode: 200,
          body: JSON.stringify(data)
        }))
      }).catch((lambdaError) => {
        if (lambdaError instanceof LambdaError) {
          callback(null, wrapHeaders(lambdaError.toLambda()));
        } else {
          // An unexpected error occurred, log the error, dont send to user.
          console.error('Unexpected error', lambdaError);
          callback(null, wrapHeaders({
            statusCode: 500,
            headers: {
              'Access-Control-Allow-Origin': '*'
            },
            body: JSON.stringify({
              message: 'An internal error occurred',
              type: 'internalError'
            })
          }));
        }
      });
    } catch (e) {
      console.error('Uncaught exception', e, e.stack);
      callback(null, wrapHeaders({
        statusCode: 500,
        body: JSON.stringify({
          message: 'An internal error occurred',
          type: 'internalError'
        })
      }));
    }
  }
}

function wrapModule(mod) {
  let out = {};
  for (let key in mod) {
    out[key] = wrapFunction(mod[key]);
  }
  return out;
}

module.exports = {
  wrapModule
};