Random event engine for SugarCube/TweeGo

backup_event.tw

:: Backup Event [event]
/*
PRIORITY: Number.MIN_SAFE_INTEGER
*/
<div class="error-view"><span class="error">No valid events found. Write some?</span></div>

event_setup.js

setup.GameEvent = (function() {
	const _target = Symbol("target");
	const _trigger = Symbol("trigger definition");
	const _weight = Symbol("weight definition");
	const _priority = Symbol("priority definition");
	const _triggerFunc = Symbol("trigger function");
	const _weightFunc = Symbol("weight function");
	const _priorityFunc = Symbol("priority function");

	class GameEvent {
		/**
		 * @param {string} target
		 * @param {string=} trigger
		 * @param {string=} weight
		 * @param {string=} priority
		 */
		constructor(target, trigger, weight, priority) {
			if(arguments.length < 1) {
				throw new TypeError("Target has to be specified");
			}
			this[_target] = String(target);
			if(!this[_target]) {
				throw new TypeError("Target has to be a non-empty string");
			}
			this[_trigger] = trigger;
			this[_weight] = weight;
			this[_priority] = priority;
			if(trigger) {
				this[_triggerFunc] = new Function("c", "return !!(" + trigger + ")");
			}
			if(weight) {
				this[_weightFunc] = new Function("c", "return Number(" + weight + ")");
			}
			if(priority) {
				this[_priorityFunc] = new Function("c", "return Math.round(" + priority + ")");
			}
		}

		get target() { return this[_target]; }
		get trigger() { return this[_trigger]; }
		get weight() { return this[_weight]; }
		get priority() { return this[_priority]; }

		/**
		 * @param {any=} context
		 * @returns {boolean} - true if the event is possible in this context
		 */
		isPossible(context) {
			try {
				return this[_triggerFunc] ? this[_triggerFunc](context || {}) : true;
			} catch(ex) {
				console.log(ex);
				return false;
			}
		}

		/**
		 * @param {any=} context
		 * @returns {number}
		 */
		calcWeight(context) {
			try {
				return this[_weightFunc] ? this[_weightFunc](context || {}) : 1.0;
			} catch(ex) {
				console.log(ex);
				return 0.0;
			}
		}

		/**
		 * @param {any=} context
		 * @returns {number}
		 */
		calcPriority(context) {
			try {
				return this[_priorityFunc] ? this[_priorityFunc](context || {}) : 0;
			} catch(ex) {
				console.log(ex);
				return Number.MIN_SAFE_INTEGER;
			}
		}
	}

	return GameEvent;
})();

/**
 * @property {GameEvent[]}
 */
setup.events = Story.lookup("tags", "event")
	.map(function(p) {
		var triggersRE = /^TRIGGER:\s*(\S.*?)$/m;
		var weightsSE = /^WEIGHT:\s*(\S.*?)$/m;
		var prioritiesSE = /^PRIORITY:\s*(\S.*?)$/m;
		var trigger = triggersRE.exec(p.text);
		var weight = weightsSE.exec(p.text);
		var priority = prioritiesSE.exec(p.text);
		return new setup.GameEvent(p.title, trigger ? trigger[1] : "", weight ? weight[1] : "", priority ? priority[1] : "");
	});

/**
 * Return an array of possible events and their current weights given the context.
 * @param {any=} context
 */
setup.pickEvent = function(context) {
	var possibleEvents = setup.events
		.filter((ev) => ev.isPossible(context))
		.map((ev) => ({ event: ev, weight: ev.calcWeight(context), prio: ev.calcPriority(context) }))
		.sort((d1, d2) => (d1.prio - d2.prio));
	if(possibleEvents.length > 0) {
		const maxPrio = possibleEvents.last().prio;
		possibleEvents = possibleEvents.filter((evData) => evData.prio === maxPrio);
	}	
	return possibleEvents;
}

orcs_attack.tw

:: Orcs Attack! [event]
/*
TRIGGER: c.isNight() && c.partyHealth() > 25 && c.isAreaTag("wilderness") && c.isAreaTag("orc")
WEIGHT: 5 + (c.partyHealth() / 30)
PRIORITY: 0
*/
This is an example event.

weighted_random.js

/**
 * @param {any[]} weights
 * @param {() => number} [rnd]
 */
function weightedRandom(weights, rnd) {
	if(!weights || !weights.length) {
		return undefined;
	}
	rnd = rnd || Math.random;
	var fallback = weights.last();
	var pick = rnd() * weights.reduce((sum, ch) => sum + ch.weight, 0);
	return (weights.find((ch) => (pick -= ch.weight) <= 0) || fallback);
}
setup.weightedRandom = weightedRandom;