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)];

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

    if (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 };
    }
}