isleward/src/server/config/itemEffects/castSpellOnHit.js

//Imports
const spellBaseTemplate = require('../spells/spellTemplate');

//Helpers
const getItemEffect = item => {
	return item.effects.find(e => (e.type === 'castSpellOnHit'));
};

const doesEventMatch = (firedEvent, eventCondition) => {
	if (
		!firedEvent ||
		(
			eventCondition.targetNotSelf === false &&
			firedEvent.target === firedEvent.source
		)
	)
		return false;

	const foundNonMatch = Object.entries(eventCondition).some(([k, v]) => {
		if (v !== null && typeof(v) === 'object') {
			if (!doesEventMatch(firedEvent[k], v))
				return true;

			return false;
		}

		return firedEvent[k] !== v;
	});

	return !foundNonMatch;
};

const shouldApplyEffect = (itemEffect, firedEvent, firedEventName) => {
	const { rolls: { chance, combatEvent: { [firedEventName]: eventCondition } } } = itemEffect;

	if (!eventCondition || !doesEventMatch(firedEvent, eventCondition))
		return false;

	if (chance !== undefined && Math.random() * 100 >= chance)
		return false;

	return true;
};

const handler = (obj, item, event, firedEventName) => {
	const itemEffect = getItemEffect(item);

	if (!shouldApplyEffect(itemEffect, event, firedEventName))
		return;

	const { rolls: { castSpell, castTarget } } = itemEffect;

	const spellConfig = extend({}, castSpell);
	spellConfig.noEvents = true;

	const scaleDamage = spellConfig.scaleDamage;
	delete spellConfig.scaleDamage;

	if (scaleDamage) {
		if (scaleDamage.s_useOriginal) {
			scaleDamage.s_useOriginal.forEach(s => {
				spellConfig[s] = event.spell[s];
			});
		}

		if (scaleDamage.percentage)
			spellConfig.damage *= (scaleDamage.percentage / 100);
	}

	const spellName = 'spell' + spellConfig.type.replace(/./, spellConfig.type.toUpperCase()[0]);
	const spellTemplate = require(`../spells/${spellName}`);

	const builtSpell = extend({ obj }, spellBaseTemplate, spellTemplate, spellConfig);

	let target = event.target;
	if (castTarget === 'self')
		target = obj;
	else if (castTarget === 'none')
		target = undefined;

	builtSpell.cast({ target });
};

//Effect
module.exports = {
	events: {
		afterGiveHp: function (item, event) {
			handler(this, item, event, 'afterGiveHp');
		},

		afterDealDamage: function (item, event) {
			handler(this, item, event, 'afterDealDamage');
		},

		afterPositionChange: function (item, event) {
			handler(this, item, event, 'afterPositionChange');
		}
	}
};