updux/src/Updux.js

import R from 'remeda';

import { Action, ActionGenerator } from './actions.js';

export class Updux {
    #localInitial = {};
    #subduxes = {};
    #actions;
    #mutations = {};
    #config = {};

    constructor(config = {}) {
        this.#config = config;
        this.#localInitial = config.initial ?? {};
        this.#subduxes = config.subduxes ?? {};

        this.#actions = R.mergeAll([
            config.actions ?? {},
            ...Object.values(this.#subduxes).map(R.prop('actions')),
        ]);
    }

    get actions() {
        return this.#actions;
    }

    get initial() {
        if (Object.keys(this.#subduxes).length === 0) return this.#localInitial;

        return Object.assign(
            {},
            this.#localInitial,
            R.mapValues(this.#subduxes, ({ initial }) => initial),
        );
    }

    get reducer() {
        return (state, action) => this.upreducer(action)(state);
    }

    get upreducer() {
        return (action) => (state) => {
            const mutation = this.#mutations[action.type];

            if (mutation) {
                state = mutation(action.payload, action)(state);
            }

            return state;
        };
    }

    setMutation(action, mutation) {
        this.#mutations[action.type] = mutation;
    }
}