bfo-publisher

v1.0.4

Published

a year ago

Interface with a BFO Publisher web-service

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BFO Publisher

bfo-publisher

A simple interface to a BFO Publisher web service.

Example (NodeJS)

npm install bfo-publisher

The module can be loaded as an ES6 module or a CommonJS module.

import * as fs from "node:fs";                  // ES6
import Publisher from "bfo-publisher";          // ES6
// const fs = require("fs");                    // CommonJS
// const Publisher = require("bfo-publisher");  // CommonJS

// The message you want to send: the actions and formats
// are defined in the BFO Publisher documentation.
let action = "convert";
let message = {
    put: [
        {
          content: fetch("http://example.com/test.html")
          /* "path" and "content_type" are derived from the fetch */
        },
        {
          content: "body { margin: 0 }",
          path: "my-stylesheet.css",
          content_type: "text/css"
        },
        {
          content: new Blob([myuint8array], { type: "image/png" }),
          path: "my-image.png"
          /* "content_type" is derived from the Blob */
        }
    ]
};

// Send a message, wait for the response, process it.
// Multiple messages can be sent; call disconnect() when finished
const publisher = new Publisher("http://localhost:8080/");
publisher.build(action, message).send().then((response) => {
    fs.writeFileSync("out.pdf", response.content);
}).finally(() => {
    publisher.disconnect();
});

Example (Browser)

Non-module use in a browser is shown here - the code defines two classes (Publisher and PublisherMessage). Any HTMLDocument or XMLDocument can be specified in a browser as a content object for conversion. This example shows how to make a button to download the current page as a PDF

<!DOCTYPE html>
<html>
 <head>
  <script src="https://publisher.bfo.com/public/publisher.js"></script>
  <script>
   const publisher = new Publisher("http://localhost:8080/");
   function convert(e) {
     let src = e.srcElement;
     publisher.build("convert", {
       put: [ { content: document } ]
     }).send().then((response) => {
       let a = document.createElement("a");
       let blob = new Blob([response.content],{type:response.content_type});
       a.href = URL.createObjectURL(blob);
       a.download = "file.pdf";
       a.addEventListener("click", (e) => {
         setTimeout(() => { URL.revokeObjectURL(a.href); }, 500);
         return true;
       });
       a.click();
     }).catch((e) => {
       console.log(e);
     });
   }
   function initialize() {
     document.getElementById("button").addEventListener("click", convert);
   }
   window.addEventListener("DOMContentLoaded", initialize);
  </script>
 </head>
 <body>
  <button id="button">Download this page as a PDF</button>
 </body>
</html>

It can also be used as an ES6 module in a browser like this:

<script type="module">
 import Publisher from "https://publisher.bfo.com/public/publisher-module.js";
 const publisher = new Publisher("http://localhost:8080/");
 // ... etc
</script>

The code uses the the browser WebSocket implementation, so has no dependencies. We strongly recommend you host the script yourself for production use.

Detail

The API is a simple wrapper around the BFO Publisher Web Service, which can be downloaded and run (locally or on another server; all the examples on this page assume it's accessible at http://localhost:8080/).

To use the API:

Create a new Publisher object
Call build(type, parameters), where type is one of the actions described in the web-service: usually this will be convert
Call send() on the returned object. This returns a Promise which will resolve with the responses to your request. If the server responds with an error, the Promise is rejected.
Repeat as required; multiple messages can be sent at once. When done call publisher.disconnect() to close the socket.

The object returned from send() is also an EventTarget and will emit log events if the action was convert. The message formats are fully described in the BFO Publisher documentation, but with some minor additions to make life easier:

The content key (for content being sent to BFO Publisher for conversion) can be specified as a string, Uint8Array or ArrayBuffer, or as a Promise that will eventually return one of those (from a Blob or a fetch(), as shown in the example above).
On a browser the content key can be an HTMLDocument or XMLDocument. If it's the current document, the current document stylesheets and resources such as images are sent with the request. Scripts are not sent (they're not processed by BFO Publisher). The document is sent as it currently is, so will reflect any changes to the DOM after the file was loaded.

The Publisher class takes a URL in the constructor, but can also accept an object with the following keys for configuration

url - the URL of the Publisher instance. Required
authorization - an Authorization key which will be used as the default for every message.
min_backoff - if the server is disconnected or fails to connect, the number of milliseconds before it's retried.
max_backoff - if the server doesn't reconnect on the first attempt, the delay will be quadrupled on every attempt until
callback - a callback function which will be called if the server sends a callback to request authorization to access a URL - typically a username and password. The method should modify the supplied list of callbacks in place and return.

The url (string) and connected (boolean) properties on the Publisher object show the current state of the connection.

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bfo-publisher

Example (NodeJS)

Example (Browser)

Detail