HTML to PDF

Application that fetches an URL and converts it to PDF

Installation

• Copy the .env example file: cp .env.example .env
• Change the PDF_HASH_KEY in .env
• Run the server with npm start

Heroku

• heroku create --region eu APPNAME
• heroku buildpacks:add jontewks/puppeteer
• git push heroku master

Health endpoint

Calling the endpoint /health without any parameter yields a 200 OK response if the server is running

Usage

Send a GET request with the following query parameters :

• url: URL to print as PDF (should be URI encoded)
• name: PDF filename (the query param can be changed by the FILENAME_QUERY_PARAM environment variable)
• hash: HMAC(sha256) signature of the URL with the PDF_HASH_KEY present in the environment variables

Configuration

The serverside app can be configured with these environment variables :

• PDF_HASH_KEY: The key used to sign the URL (REQUIRED)
• PUPPETEER_PAGE_OPTIONS: JSON options that will be passed to the Puppeteer page
• FILENAME_QUERY_PARAM: query parameter used to retreive the filename
• UNTITLED_FILENAME: default filename

Additionally, you can configure the error messages with the following environment variables :

• MESSAGES_MISSING_URL: Missing URL
• MESSAGES_INVALID_URL: Invalid URL
• MESSAGES_INVALID_SIGNATURE: Invalid signature
• MESSAGES_GENERATING_FOR_URL: Generating PDF for :url
• MESSAGES_DONE_IN_SECONDS: Done in :duration
• MESSAGES_ERROR_ON_RETRIEVAL: An error occured during the URL retrieval Words started with a colon are variables that will be replaced bu the value at runtime.

Example

// Assuming we want to create a PDF file, named 'output.pdf'
// of the website 'https://website.com', and this app is
// exposed at the server address: 'https://server.com'

const crypto = require('crypto')

const filename = 'output.pdf'
const url = 'https://website.com'
const key = 'YOUR-PDF_HASH_KEY-SET-IN-DOTENV'

// Generates the signature
const signature = crypto
    .createHmac('sha256', key)
    .update(url)
    .digest("hex")

// echoes the signature
console.log(signature)

// Generates the link to download the PDF
const signedUrl = 'https://server.com?'
    + 'url=' + encodeURIcomponents(url)
    + '&name=' + filename
    + '&hash=' + signature

The signedUrl should look like this :

https://server.com?url=https%3A%2F%2Fwebsite.com&name=output.pdf&hash=e02a0fce77bfb2b992cd2a93758e53af804ad6c61731ea40c0c1c0c5a69c192d

You can use it to download the file directly :

// Downloading the file with fetch
fetch(signedUrl, { method: 'GET' })
    .then(res => res.blob())
    .then(blob => {
        const file = window.URL.createObjectURL(blob)
        window.location.assign(file)
    })

Or set it as the destination of a download link :

<a id="downloadLink" href="#" download> Download the PDF</a>

<script>
    const link = document.getElementById('downloadLink')
    link.setAttribute('href', 'signedUrl')
</script>