dbjs persistent layer handler

dbjs-persistent-layer-handler.js

'use strict';

var Database    = require('dbjs')
  , serialize   = require('dbjs/_setup/serialize/value')
  , unserialize = require('dbjs/_setup/unserialize/value')
  , DbjsEvent   = require('dbjs/_setup/event')

  , db = new Database();

// 1. Save
// Below configuration also handles changes made to schema, if that's an issue, either you may
// register this listener after schema is loaded or within listener filter which data you
// want to pass to persisent layer.
db.objects.on('update', function (event) {
	// Get serialized id
	var id = event.object.__valueId__;
	// Get serialized modification timestamp (microseconds accuracy)
	var stamp = String(event.stamp);
	// Get serialized value
	var value = serialize(event.value);

	// Either all events can be saved to persistent layer, or you can remove deleted records and
	// update others (this is not perfectly safe if you work with offline clients that can send
	// updates after some period of time)
	if (!value) {
		// Delete
	} else {
		// Create or update
	}
});


// 2. Restore
// `data` is collection of data you get from your persistent layer
data.forEach(function (item) {
	var value = unserialize(item.value, db.objects), proto;
	if (value && value.__id__ && (value.constructor.prototype === value)) {
		// Value is a constructor prototype, for seamless object creation we'll pass this information to
		// object unserialize function
		proto = value.constructor;
	}
	new DbjsEvent(db.objects.unserialize(item.id, proto), value, Number(item.stamp));
});