"use strict";var PubSub=require("sublish").PubSub,slice=Array.prototype.slice,isArray=Array.isArray?Array.isArray:function(arr){return Object.prototype.toString.call(arr)==="[object Array]"},contains=Array.prototype.indexOf?function(arr,el){return!!~arr.indexOf(el)}:function(arr,el){for(var i=0;i<arr.length;i++){if(arr[i]===el){return true}}return false};function ext(dest){var srcs=slice.call(arguments,1);for(var i=0;i<srcs.length;i++){var src=srcs[i];for(var key in src){if(src.hasOwnProperty(key)){dest[key]=src[key]}}}return dest}function parseComputedConfig(args){var config=args[0];if(typeof config==="function"){config={compute:args[0]};if(args.length>1){if(typeof args[1]==="function"){config.write=args[1];if(args.length>2){config.watch=args[2]}}else{config.watch=args[1]}}}return config}function obs(config){function observable(value){if(arguments.length){if(typeof observable.write==="function"){observable.write.call(observable.context,value)}else{throw new Error("This observable cannot be written to!")}}else{if(typeof observable.read==="function"){return observable.read.call(observable.context)}else{throw new Error("This observable cannot be read from!")}}}ext(observable,PubSub.prototype,{context:config.context||observable,read:config.read,write:config.write,onNotify:function(onNotify){return function(){onNotify.call(observable)}}(config.onNotify||function(){}),_initialValue:config.value,_currentValue:config.value,_previousValue:undefined,_subscriptions:[]},obs.fn);PubSub.apply(observable);if(config.watch){observable.watch.apply(observable,isArray(config.watch)?config.watch:[config.watch])}return observable}obs.fn={__is_obs__:true,notify:function(){this.dirty=this._currentValue===this._initialValue;this.publish(this._currentValue,this._previousValue)},peek:function(){return this._currentValue},commit:function(){this._initialValue=this._currentValue;this.dirty=false},reset:function(){this._previousValue=this._currentValue;this._currentValue=this._initialValue;this.notify()},watch:function(){var args=slice.call(arguments,0),sub,i;for(i=0;i<args.length;i++){sub=args[i];if(contains(this._subscriptions,sub)){continue}if(sub&&typeof sub.subscribe==="function"){sub.subscribe(this.onNotify);this._subscriptions.push(sub)}}return this},unwatch:function(){var subs=slice.call(arguments,0),allSubs=this._subscriptions,i,sub;for(i=0;i<subs.length;i++){sub=subs[i];if(sub&&typeof sub.unsubscribe==="function"){sub.unsubscribe(this.onNotify)}}this._subscriptions=[];for(i=0;i<allSubs.length;i++){sub=allSubs[i];if(!contains(subs,sub)){this._subscriptions.push(sub)}}return this},dismiss:function(){this.unwatch.apply(this,this._subscriptions)}};obs.prop=function(initialValue){return obs({read:function(){return this._currentValue},write:function(value){this._previousValue=this._currentValue;this._currentValue=value;this.notify()},value:initialValue})};obs.computed=function(config){config=parseComputedConfig(arguments);var observable=obs(ext({},config,{read:function(){return observable._currentValue},onNotify:function(){this._previousValue=this._currentValue;this._currentValue=config.compute.call(this.context);this.notify()}}));if(config.compute){observable._initialValue=config.compute.call(observable.context);observable._currentValue=observable._initialValue}if(config.watch){observable.watch.apply(observable,isArray(config.watch)?config.watch:[config.watch])}return observable};obs.computed.lazy=function(config){config=parseComputedConfig(arguments);var changed=true;var observable=obs(ext({},config,{context:config.context,read:function(){if(changed){changed=false;observable._previousValue=observable._currentValue;observable._currentValue=config.compute.call(this);observable.notify()}return observable._currentValue},write:config.write,onNotify:function(){changed=true},watch:config.watch}));return observable};module.exports=obs;