updux/src/selectors.js

import R from 'remeda';

export function buildSelectors(
    localSelectors,
    findSelectors = {},
    subduxes = {},
) {
    const subSelectors = Object.entries(subduxes).map(
        ([slice, { selectors }]) => {
            if (!selectors) return {};
            if (slice === '*') return {};

            return R.mapValues(
                selectors,
                (func) => (state) => func(state[slice]),
            );
        },
    );

    let splat = {};

    for (const name in findSelectors) {
        splat[name] =
            (mainState) =>
            (...args) => {
                const state = findSelectors[name](mainState)(...args);

                return R.merge(
                    { state },
                    R.mapValues(
                        subduxes['*']?.selectors ?? {},
                        (selector) =>
                            (...args) => {
                                let value = selector(state);
                                if (typeof value !== 'function') return value;
                                return value(...args);
                            },
                    ),
                );
            };
    }
    return R.mergeAll([...subSelectors, localSelectors, splat]);
}