Puddle-hub

Corpus CRUD API wrapper

###Features: [X] Minimum dependencies [X] Can be connectd in a branched fashion, can't in circular
Returns a Hub class which is:
[X] has .on method to hook to events [X] emits: create,remove,update events [X] implements .create,.remove, .update methods [X] implements .getState method which returns internal state [X] implements .connect method which allows to bi-directionally bind it to another instance of same class. [X] Constructor takes optional state [X] Object agnostic (does not care what to sync)

###Installation:

npm install puddle-hub
npm test        # optional

###Usage:

API

.create(id, obj, [nodeId])
.remove(id, [nodeId])
.update(id, obj, [nodeId])
.reset(state, [nodeId])
.on('create', function(id,obj) {...}, [nodeId])
.on('remove', function(id) {...}, [nodeId])
.on('update', function(id,obj) {...}, [nodeId])
.on('reset', function(state) {...}, [nodeId])
.connect(hub)  //also fires reset event

CRUD API has optional last parameter nodeId which is used for echo prevention. Please see Echo section below.

####Basic usage:

var Hub = require('puddle-hub');
var uuid = require('node-uuid');
var newId = uuid();

var state = {};
state[uuid()]='Obj1';
state[uuid()]='Obj2';

var hub = new Hub(state);  //optionaly pass in init state

hub.on('create', function (id,obj) {
    console.log('Create event called with',obj);
});
hub.create(newId,'Obj3'); //here an event will fire and you'll see in Console
// Create event called with Obj3

console.log(hub.getState()); // returns current state of the internal hash including added Obj3 i.e.
//{ '5e5c22b8-2053-47d4-a9e4-d4edc92337d0': 'Obj1',
//    'd165ab1e-d2be-4b4b-956e-97db5ad55597': 'Obj2',
//    '0ac96ebf-1c0b-4b77-8585-8012302aa56e': 'Obj3' }

####Chaining:

var Hub = require('puddle-hub');
var uuid = require('node-uuid');
var state = {};
state[uuid()]='Obj1';
state[uuid()]='Obj2';

var one = new Hub(state);  //pass in init state       
var two = new Hub();
var three = new Hub();

var obj = {name:'Object'}; //can be anything, i.e. {},[],''

two.connect(one);
console.log(three.getState()); // {}
three.connect(two);
console.log(three.getState()); // because .connect() pulls in other instance's state.
                               //{ 'bae0cdf5-ddf5-45b4-aa46-babe9424b5e7': 'Obj1',
                               //    'a45c6c6f-8f5a-4dab-8872-590c363da7cb': 'Obj2' }


one.on('create', function (id,obj) {
   console.log('One got an object ',obj);
});
three.on('create', function (id,obj) {
   console.log('Three got an object ',obj);
});

//events propogate through the chain
one.create(uuid(),obj); // 'Three got an object obj' && 'One got an object obj'

//both ways
three.create(uuid(),obj);// 'Three got an object obj' && 'One got an object obj'

Echo

If you set a listener on hub i.e. :

var Hub = require(‘puddle-hub’);
var hub = new Hub();
hub.on('create',function (id, obj) {
    console.log('Event fired');
});

and issue an action

hub.create('1', {}); // Event fired

Than two things will happen:

• that action will propogate through chain of conneted HUBs (perhaps to other machines via socket.io)
• you will also hear an 'echo' in a form of event fired immediately with object you have just supplied to hub.create.

If you want to avoid echo than supply a nodeId as a last parameter to event linteners like that:

var Hub = require('puddle-hub');
var uuid = require('node-uuid');
var hub = new Hub();
var obj = {};


hub.on('create', function (id, obj) {
    console.log('Event fired');
}, hub.nodeId);

hub.create(uuid(), 'Some other ID'); // Event fired

//two below are the same:
hub.create(uuid(), obj); // Event NOT fired
hub.create(uuid(), hub.nodeId); // Event NOT fired

    

Please note that both event listener and method invokation has to have that same unique ID. Internally calling method w/o nodeId is the same as calling it with hub.nodeId In other words event is not fired if it was registered with same ID as method was called. That only affects local 'echo' events. Other hubs will get their event listeners fired anyway.

If you have two local consumers of HUB and none of them wants to hear his own method calls but wants to hear others than best way would be to create second Hub() instance and chain it accordingly.

Contributors

• Fritz Obermeyer https://github.com/fritzo
• Yan T. https://github.com/yangit

Puddle was factored out of Pomagma in 2014.

License

Copyright 2013-2014 Fritz Obermeyer. Puddle is licensed under the MIT license.