havana-component-handler

Havana component handler

An HTML response handler.

Havana component handler works with a request/response dispatcher such as Havana server, Havana browser or a library with an interchangeable API. When a dispatcher publishes a response.received event Havana component handler will publish a route.find event for consumption by a router such as Havana router or a library with an interchangeable API.

Havana component handler consumes routes of the following structure (note how components can be nested):

[
  {
    'url': '/',
    'method': 'GET',
    'components': [
      {
        'component': 'page',
        'properties': {
          'header': {
            'component': 'header',
            'properties': {
              'logo': '/public/logo.svg',
            },
          },
          'content': 'Hello world',
        },
      },
    ],
  },
]

When the router publishes a route.found event Havana component handler will convert the components array to the following flattened structure:

[
  {
    'children': [ 2 ],
    'component': 'page',
    'id': 1,
    'properties': {
      'content': 'Hello world',
      'header': null,
    },
    'state': 'not rendered',
  },
  {
    'component': 'header',
    'id': 2,
    'parent': 1,
    'properties': {
      'logo': '/public/logo.svg',
    },
    'propertyKey': 'header',
    'state': 'not rendered',
  }
]

Havana component handler then publishes a components.compile event for consumption by Havana component compiler or a library with an interchangeable API. The component compiler renders the components array into an HTML string, publishing a components.compiled event when complete. Havana component handler subscribes to the components.compiled event and in turn publishes a response.send event publishing the rendered HTML string for consumption by the dispatcher.

How to install

npm install havana-component-handler

How to use

import ComponentHandler from 'havana-component-handler';
import Event from 'havana-event';
import Router from 'havana-router';
import Server from 'havana-server';

const event = new Event();

const reporting = {
  'level': 2, 
  'reporter': console.log,
};

const server = new Server({
  'event': event,
  'reporting': reporting,
});

new Router({
  'event': event,
  'reporting': reporting,
  'routes': [
    {
      'url': '/',
      'method': 'GET',
      'components': [
        {
          'component': 'page',
          'properties': {
            'content': 'Hello world',
          },
        },
      ],
    },
  ],
});

// Add a component compiler here

new ComponentHandler({
  'event': event,
  'reporting': reporting,
});

server.listen( 3000 );

Event list

Events take the form of Havana event or a library with an interchangeable API.

Publish

• response.handler.register: Signifies that Havana component handler will now attempt to handle requests.
• route.find: Signifies that a request has been received and Havana component handler requires a matching route.
• components.compile: Signifies that Havana component handler requires a components array to be rendered into an HTML string.
• response.send: Signifies that Havana component handler has received an HTML string for consumption by a request/response dispatcher.
• response.handler.error: Signifies that Havana component handler was unable to provide a response.

Subscribe

• request.received: Allows a request/response dispatcher to notify Havana component handler that it has received a request, publishing the request data for consumption by Havana component handler.
• route.found: Allows a router to notify Havana component Handler that it has found a route, publishing the route data for consumption by Havana component handler.
• components.compiled: Allows a component compiler to notify Havana component handler that it has completed rendering the components array into an HTML string.

ES2015+

Havana component handler is written using ES2015+ syntax.

However, by default this module will use an ES5 compatible file that has been compiled using Babel.

In the dist directory there are four files, the default is handler.server.js. The default when using a client-side bundler that supports the browser field spec is handler.browser.js.

Havana component handler currently requires the Babel polyfill. You are expected to supply this yourself. However, as a courtesy you will also find handler.server.with-polyfill.js and handler.browser.with-polyfill.js in the dist directory.