NPM module for common functions in backend

useful in a setup with

• serverless stack
• AWS

Usage

All functions can be imported from their respective modules (results in lowest packages size), e.g.:

import { sleep } from 'blob-common/core/sleep';
import { btoa } from 'blob-common/core/base64';

All functions can be imported directly from the core, e.g.:

import { sleep, btoa } from 'blob-common';

NB: the sanitize function is not included in the core, due to the relatively large size of imported package.

Generic functions

Module	Function	Description
/base64	otob(object)	takes an object and coverts to base64 string
/base64	btoa(base64String)	inverse: takes a base64 string and returns an object
/date	now()	returns a string of the current date in format yyyy-mm-dd
/date	diffDate(dateStr, days)	takes a dateStr in standard format and difference, returns a dateStr in the standard format
/date	expireDate(dateStr)	takes a dateStr in standard format and returns a date 30 days later in the standard format
/handler	handler(lamdba)	wrapper function for event handler (to log errors)
/handler	getUserFromEvent(event)	returns the userId (from AWS cognito user pool) of authenticated User
/handler	apiCall(promise)	async wrapper for promise, returns the a tuple [err, result]
/ids	newPhotoId()	returns a newly generated photoId (starts with P)
/ids	newGroupId()	returns a newly generated groupId (starts with G)
/ids	newAlbumId()	returns a newly generated albumId (starts with A)
/RND	RND	returns a random number between 1 and 15, usable as an index key in dynamoDb to spread database load on very large queries
/sleep	sleep(ms)	await sleep(1000) sleeps for 1 second. Used in tests to wait for dynamoDB to have processed updates
/sanitize	sanitize(dirty)	sanitizes a string from any sequences that may cause security issues (e.g. when using name string in an email message)

DynamoDb functions

Module	Function	Description
/db	dynamoDb.get(params)	returns a promise for DynamoDb function using the params. Uses AWS-SDK, refer to official docs for more info. Also has functions .put, .update, .delete, query, transact (for TransactWrite)
/db	dbUpdate(PK, SK, key, newVal)	returns a promise for a single update on the database, setting key to new value provided in newVal
/db	dbUpdateMulti(PK, SK, newKV)	returns a promise for a single update on the database at multiple keys. newKV is an object containing keys to be updated with new values
/dbClean	cleanRecord(object)	removes keys RK, datePK, dateSK, cognitoId from the object - useful for storing data as derived items in other items (e.g. owner as part of photo object)
/dbCreate	dbItem(object)	returns an object with extended keys for database: createdAt, RK, datePK, dateSK
/dbCreate	dbCreateItem(object)	returns a promise to create an expanded item in database from object (object must have PK and SK keys)

Some caveats on the specific dynamoDB functions:

• eu-central-1 is the standard region chosen
• to work, there should be a process.env.photoTable variable for all functions (except dynamoDb)
• database must have PK (string) as primary key, and SK (string) as sortkey

S3 and SES functions

Module	Function	Description
/s3	s3.getMetadata(params)	returns a promise for an s3 function using the params.
/s3	s3.delete(params)	deletes stuff.
/s3	s3.get(params)	gets an object.
/s3	s3.list(params)	lists a bucket probably.
/s3	s3.getSignedUrl(params)	gets a signed url for ADDING a file to s3 (for uploads).
/s3	s3.getSignedUrlGet(params)	gets a signed url for READING a file from s3.
/ses	ses.send(params)	sends an email from ses using params - returns promise
/ses	ses.sendEmail(params)	sends an email from ses using {toEmail, fromEmail, subject, data, textData} - returns promise

NB:

• toEmail can be either a string or an array of strings (multiple recipients)

Caveats:

• s3 function uses s3 bucket specified in process.env.photoBucket or process.env.devBucket

email helper functions

Module	Function	Description
/email	emailBody(rows)	returns email body with rows
/email	row(cells)	generic row containing array of cells
/email	headerRow(logoSrc, frontendUrl)	header row with logo, links to frontend
/email	footerRow
/email	photoRow(photoSrc, linkUrl)	row containing (header) photo
/email	textCell(subtype)	cell containing greeting, paragraph or buttonEscape (small text with link)
/email	dividerCell(dividerSrc)
/email	buttonCell(text, link)
/email	codeCell(code)	big text block centered with code
/email	signatureCell(src)	left aligned signature under email
/email	greeting(text)
/email	paragraph(text)
/email	buttonEscape(url)
/email	makeEmailSrc(url, width, height)	returns publicly accessible url for image in S3 bucket

Caveats:

• makeEmailSrc uses s3 bucketname from process.env.bucket or process.env.devBucket

Cognito functions

Module	Function	Description
/cognito	cognito.disableUser(userId)	disables a user in the cognito user pool
/cognito	cognito.deleteUser(userId)	deletes a user in the cognito user pool

Caveats:

• uses cognito userpool id from process.env.userPoolId or process.env.devUserPoolId