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WEB-EXTENSIONS-HOWTO.md

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Web extensions

If some adapter want to be available under same port as web adapter, it should implement the web extension functionality.

First, it must have a common.webExtension flag in io-package.json file that points to thw web extension file. Like "webExtension": "lib/web.js".

Second, common.native.webInstance flag in io-package.json has to point to the instance name of the web-adapter for which the extension should be loaded. Or simply load it for all instances via "webInstance": "*".

Third, the file lib/web.js (or whatever) must exist, and it must export a class.

/**
 * Web extension example
 *
 * @class
 * @param {object} server http or https node.js object
 * @param {object} webSettings settings of the web server, like <pre><code>{secure: settings.secure, port: settings.port}</code></pre>
 * @param {object} adapter web adapter object
 * @param {object} instanceSettings instance object with common and native
 * @param {object} app express application
 * @return {object} class instance
 */
function ExtensionExample(server, webSettings, adapter, instanceSettings, app) {
    this.app         = app;
    this.config      = instanceSettings ? instanceSettings.native : {};
    const that       = this;

    // instanceSettings and this.config contain instance config (not web adapter, but this one with web-extension)
    this.config.demoParam = this.config.demoParam || 'demo';

    this.unload = function () {
        return new Promise(resolve => {
            adapter.log.debug('Demo extension unloaded!');
            
            // unload app path
            const middlewareIndex = app._router.stack.findIndex(layer => 
                layer && layer.route === '/' + that.config.demoParam);
                
            if (middlewareIndex !== -1) {
                // Remove the matched middleware
                app._router.stack.splice(middlewareIndex, 1);
            }
            
            resolve();
        });
    };

    // Optional: deliver to web the link to Web interface
    this.welcomePage = () => {
        return {
            link: 'example/',
            name: 'Example',
            img: 'adapter/example/example.png',
            color: '#157c00',
            order: 10,
            pro: false
        };
    }

    // Optional. Say to web instance to wait till this instance is initialized
    // Used if initalisation lasts some time
    this.readyCallback = null; 
    this.waitForReady = cb => {
        this.readyCallback = cb;
    }

    // self invoke constructor
    (function __constructor () {
        adapter.log.info('Install extension on /' + that.config.demoParam);
        
        that.app.use('/' + that.config.demoParam, (req, res) => {
            res.setHeader('Content-type', 'text/html');
            res.status(200).send('You called a demo web extension with path "' + req.url + '");
        });
        
        // inform web about that all routes are installed
        this.readyCallback && this.readyCallback(that);
    })();
}

module.exports = ExtensionExample;

common.mode could be:

  • daemon - the instance will be started, but if main.js returns utils.EXIT_CODES.ADAPTER_REQUESTED_TERMINATION as exit code, the instance will not be restarted.
  • extension - the instance will never be started, as it runs only as part of web instance

Examples

Following adapters support web-extensions: