PureState

pure-state.js

let captured_deps = []
let capturing_deps = false

function refresh(node){
	const depended_values = []
	for (let i = 0; i < node.dependencies.length; ++i) {
		depended_values.push(node.dependencies[i].value)
	}
	node.value = node.compute.apply(null, depended_values)

	for (let i = 0; i < node.depended_by.length; ++i) {
		refresh(node.depended_by[i])
	}
}

module.exports = function state(compute){
	function wrap_function(compute){
		if (typeof compute !== "function") {
			return function(){
				return compute
			}
		} else {
			return compute
		}
	}
	node.compute = wrap_function(compute)

	function node(new_compute){
		if (capturing_deps) {
			captured_deps.push(node)
		}
		if (new_compute !== undefined){
			node.compute = wrap_function(new_compute)
			refresh(node)
		}
		return node.value
	}

	node.depended_by = []
	captured_deps = []
	capturing_deps = true
	node.compute()
	capturing_deps = false
	node.dependencies = captured_deps
	for (let i = 0; i < captured_deps.length; ++i) {
		captured_deps[i].depended_by.push(node)
	}

	refresh(node)

	return node
}