relu-core/modules/rp/lib/computed.js

Core for bot

var base = require("./base");
var rpConst = require("./const");

module.exports = function rpComputed(fn) {
	var p = base();
	p.constructor = rpComputed;

	var value;
	var dependencies
	var scope;

	p._get = function() {
		if(!dependencies) calculateValue();
		p.depend();
		return value;
	};

	p._getUndependend = function() {
		if(!dependencies) calculateValue();
		return value;
	};

	p._length = function() {
		if(!Array.isArray(value)) return -1;
		return value.length;
	};

	p.isConst = function() {
		return !dependencies || dependencies.every(function(dep) {
			return dep.isConst();
		});
	};

	p._writable = false;

	var disposed = false;
	p.onceDisposed(function() {
		disposed = true;
		if(dependencies) disconnect();
	});

	calculateValue();

	function disconnect() {
		var _scope = scope.slice();
		var _deps = dependencies;
		dependencies = scope = undefined;
		for(var i = 0; i < _deps.length; i++) {
			var dep = _deps[i];
			dep.removeOnceChangedListener(onDependencyChanged);
			dep.unref(p);
		}
		base.unrefAll(_scope);
	}

	function calculateValue() {
		if(disposed) return;
		var captured = base.capture(fn);
		dependencies = captured.dependencies;

		// if any of the dependencies is disposed, we are in a undefined state
		for(var i = 0; i < dependencies.length; i++) {
			if(dependencies[i].isDisposed()) {
				dependencies.length = 0;
				captured.value = undefined;
			}
		}

		scope = captured.scope;
		base.refAll(dependencies, p);
		for(var i = 0; i < dependencies.length; i++)
			dependencies[i].onceChanged(onDependencyChanged);
		var val = captured.value;
		if(val !== value) {
			var old = value;
			value = val;
			p._updated(value, old);
			p._changed();
		}
	}

	function onDependencyChanged() {
		if(!dependencies) return;
		var temp = {};
		var _deps = base.refAll(dependencies.slice(), temp);
		var _scope = base.refAll(scope.slice(), temp);
		disconnect();
		base.atAtomicEnd(function() {
			calculateValue();
			base.unrefAll(_deps, temp);
			base.unrefAll(_scope, temp);
		});
	}

	return p;
};