SugarCube 2 - Branch out of the State system to create a snapshot for later use

branch.js

(function() {
	"use strict";

	Macro.add("branch", {
		handler() {
			let id = this.args[0];
			let list = this.args.slice(1);
			
			variables()["#macro-branch"] = variables()["#macro-branch"] || {};
			variables()["#macro-branch"][id] = variables()["#macro-branch"][id] || {};

			let init = variables()["#macro-branch"][id].__init;
			let post = variables()["#macro-branch"][id].__post;

			if (init) {
				post = {};
				list.forEach(el => {
					post[el] = clone(State.getVar(el));
					State.setVar(el, clone(init[el]));
				});
			} else {
				init = {};
				list.forEach(el => {
					init[el] = clone(State.getVar(el));
				});
			}

			variables()["#macro-branch"][id] = {
				__init: init,
				__post: post
			};
		}
	});

	Macro.add("closeBranch", {
		handler() {
			let id = this.args[0];

			variables()["#macro-branch"] = variables()["#macro-branch"] || {};
			variables()["#macro-branch"][id] = variables()["#macro-branch"][id] || {};

			let post = variables()["#macro-branch"][id].__post;

			if (post) {
				Object.keys(post).forEach(el => {
					State.setVar(el, post[el])
				});
			}
		}
	});
})();

exampleUsage.tw

:: StoryInit

<<set $someVar to 0>>
<<set $anotherVar to true>>



:: Start

<<= $someVar>>
<<= $anotherVar>>

<<button "Add 50 to first variable">>
	<<set $someVar += 50>>
<</button>>

<<button "Toggle second variable">>
	<<set $anotherVar = !$anotherVar>>
<</button>>

[[Branch passage]]



:: Branch passage

<<branch "UID"
  "$someVar"
  "$anotherVar"
>>

<<set $someVar += 10>>
<<set $anotherVar to false>>

<<= $someVar>>
<<= $anotherVar>>

<<closeBranch "UID">>

[[Start]]