under-falling-skies/src/lib/store/genNextBattle.js

import * as R from 'remeda';
import chapters from './chapters.js';

const pickOne = (choices) => choices[parseInt(Math.random() * choices.length)];

function genChapter1Battle(battles) {
	const chapter = 1;

	const scenario = pickOne(
		chapters[chapter - 1].scenarios.filter(
			(s) => !battles.map(R.prop('scenario')).includes(s),
		),
	);
	const character = pickOne(
		chapters[chapter - 1].characters.filter(
			(s) => !battles.map(R.prop('character')).includes(s),
		),
	);
	const city = pickOne(
		chapters[chapter - 1].cities.filter(
			(s) => !battles.map(R.prop('city')).includes(s),
		),
	);

	return { scenario, character, city, status: 'ongoing', wave: 1 };
}

export function genChapter2Battle(battles) {
	const chapter = 2;

	const scenario = pickOne(
		chapters[chapter - 1].scenarios.filter(
			(s) => !battles.map(R.prop('scenario')).includes(s),
		),
	);
	const character = pickOne(
		chapters[chapter - 1].characters.filter(
			(s) => !battles.map(R.prop('character')).includes(s),
		),
	);
	const city = pickOne(
		chapters[chapter - 1].cities.filter(
			(s) => !battles.map(R.prop('city')).includes(s),
		),
	);

	let choices = battles.slice(0, 2).map(R.prop('character'));
	if (battles.length == 3)
		choices = choices.filter(
			(n) => n !== R.last(battles).additionalCharacters[0].selection,
		);

	return {
		scenario,
		character,
		city,
		status: 'ongoing',
		wave: 1,
		additionalCharacters: [{ choices, selection: R.first(choices) }],
	};
}

export function genNextBattle(battles = []) {
	let chapter = R.clamp(1 + parseInt(battles.length / 2), { min: 1, max: 4 });

	if (chapter === 1) return genChapter1Battle(battles);

	if (chapter === 2) return genChapter2Battle(battles);
}