resource.md

Resource

Resources provide a way to handle http requests at a root url. They must implement a handle(ctx, next) method that either handles a request or calls next() to give the request back to the router.

Resources can also be attributed with meta-data to allow the dashboard to dynamically render an editor gui for configuring a resource instance.

Events / Scripts

A Resource can execute Scripts during the handling of an http request when certain events occur. This allows users of the resource to inject logic during specific events during an http request without having to extend the resource or create their own.

For example, the Collection resource executes the get.js event script when it retrieves each object from its store. If a get.js file exists in the instance folder of a resource (eg. /my-project/resources/my-collection/get.js), it will be pulled in by the resource and exposed as myResource.scripts.get.

Class: Resource

A Resource inherits from EventEmitter. The following events are available.

• changed after a resource config has changed
• deleted after a resource config has been deleted

Inheriting from Resource:

var Resource = require('deployd/lib/resource')
  , util = require('util');
  
function MyResource(name, options) {
  // run the parent constructor
  // before using any properties/methods
  Resource.apply(this, arguments);
}
util.inherits(MyResource, Resource);
module.exports = MyResource;

• name {String}

The name of the resource.

• options {Object}

• configPath the project relative path to the resource instance
• path the base path a resource should handle
• db (optional) the database a resource will use for persistence
• config the instance configuration object
• server the server object

The following resource would respond with a file at the url /my-file.html.

function MyFileResource(name, options) {
  Resource.apply(this, arguments);

  this.on('changed', function(config) {
    console.log('MyFileResource changed', config);
  });
}
util.inherits(MyFileResource, Resource);

MyFileResource.prototype.handle = function (ctx, next) {
  if (ctx.url === '/my-file.html') {
    fs.createReadStream('my-file.html').pipe(ctx.res);
  } else {
    next();
  }
}

Overriding Behavior

Certain method's on a Resource prototype are called by the runtime. Their default behavior should be overriden to define an inherited Resources behavior.

resource.handle(ctx, next)

Handle an incoming request. This gets called by the router. Call next() if the resource cannot handle the request. Otherwise call cxt.done(err, res) when the resource is ready to respond.

• ctx {Context}

The http context created by the Router. This provides an abstraction between the actual request and response. A Resource should call ctx.done or pipe to ctx.res if it can handle a request. Otherwise it should call next().

Override the handle method to return a string:

function MyResource(settings) {
  Resource.apply(this, arguments);
}
util.inherits(MyResource, Resource);

MyResource.prototype.handle = function (ctx, next) {
  // respond with the file contents (or an error if one occurs)
  fs.readFile('myfile.txt', ctx.done);
}

resource.load(fn)

Load any dependencies and call fn(err) with any errors that occur. This is automatically called by the runtime to support asynchronous construction of a resource (such as loading files). If this method is overridden the super method must be called to support loading of the MyResource.events array.

External Prototype

This is a special type of prototype object that is used to build the dpd object. Each function on the Resource.external prototype Object are exposed externally in two places

1. To the generated dpd.js browser JavaScript client
2. To the Context.dpd object generated for inter-resource calls

Here is an example of a simple resource that exposes a method on the external prototype.

/my-project/node_modules/example.js

var util = require('util');
var Resource = require('deployd/lib/resource');
function Example(name, options) {
  Resource.apply(this, arguments);
}
util.inherits(Example, Resource);

Example.external = {};

Example.external.hello = function(options, ctx, fn) {
  console.log(options.msg); // 'hello world'
}

When the hello() method is called a context does not need to be provided as the dpd object is built with a context. A callback may be provided which will be executed with results of fn(err, result).

/my-project/public/hello.js

dpd.example.hello({msg: 'hello world'});

/my-project/resources/other-resource/get.js

dpd.example.hello({msg: 'hello world'});

Resource.events

• {Array}

If a Resource constructor includes an array of events, it will try to load the scripts in its instance folder (eg. /my-project/resources/my-resource/get.js) using resource.loadScripts(eventNames, fn).

MyResource.events = ['get'];

This will be available to each instance of this resource.

/my-project/node_modules/my-resource.js

MyResource.prototype.handle = function(ctx, next) {
  if(this.events && this.events.get) {
    var domain = {
      say: function(msg) {
        console.log(msg); // 'hello world'
      }
    }
    this.events.get.run(ctx, domain, ctx.done);
  }
}

/my-project/resources/my-resource/get.js

say('hello world');

Custom Dashboard

A resource can describe the dependencies of a fully custom dashboard editor ui. This will be passed to the dashboard during rendering to create a custom ui.

This example creates a custom dashboard for the Collection resource. It automatically includes pages, and separate scripts.

Collection.dashboard = {
    path: path.join(__dirname, 'dashboard')
  , pages: ['Properties', 'Data', 'Events', 'API']
  , scripts: [
      '/js/ui.js'
    , '/js/util.js'
  ]
}

• path {String}

The absolute path to this resource's dashboard

• pages {Array} (optional)

An array of pages to appear in the sidebar. If this is not provided, the only page available will be "Config" (and "Events", if MyResource.events is set).

The dashboard will load content from [current-page].html and js/[current-page].js.

Note: The "Config" page will load from index.html and js/index.js.

Note: events.html is optional - if not provided, the dashboard will load a default event editor.

• scripts {Array} (optional)

An array of extra JavaScript files to load with the dashboard pages.

Basic Dashboard

In cases where a custom ui is not practical, a resource can describe the setting to render for a basic dashboard. The following example would render a single textbox.

Proxy.basicDashboard = {
  settings: [{
    name: "remote"
    , type: "text"
    , description: "The remote server to proxy to."
  }]
}

The settings object is an array of objects with these properties:

• name {String}

The name of the property in your config object. Make sure this is something easily accessible through JavaScript, i.e. maxItems rather than "Maximum Amount of Items".

• type {String}

The type of field to render in the dashboard. Supported options are text, textarea, number, and checkbox.

• description {String}

Text to appear beneath the property in the dashboard.