updux/src/reducer.ts

import { Action, ActionCreator, createAction } from '@reduxjs/toolkit';
import { BaseActionCreator } from '@reduxjs/toolkit/dist/createAction.js';
import * as R from 'remeda';
import { Dux } from './types.js';
import { Mutation } from './Updux.js';

export type MutationCase = {
    matcher: (action: Action) => boolean;
    mutation: Mutation;
    terminal: boolean;
};

export function buildReducer(
    initialState: any,
    mutations: MutationCase[] = [],
    defaultMutation?: Omit<MutationCase, 'matcher'>,
    subduxes: Record<string, Dux> = {},
) {
    const subReducers = R.mapValues(subduxes, R.prop('reducer'));

    // TODO matcherMutation
    // TODO defaultMutation
    //
    const reducer = (state = initialState, action: Action) => {
        if (!action?.type)
            throw new Error('upreducer called with a bad action');

        let terminal = false;
        let didSomething = false;

        mutations
            .filter(({ matcher }) => matcher(action))
            .forEach(({ mutation, terminal: t }) => {
                if (t) terminal = true;
                didSomething = true;
                //
                // TODO wrap mutations in immer
                state = mutation((action as any).payload, action)(state);
            });

        if (!didSomething && defaultMutation) {
            if (defaultMutation.terminal) terminal = true;

            state = defaultMutation.mutation(
                (action as any).payload,
                action,
            )(state);
        }

        if (!terminal && Object.keys(subduxes).length > 0) {
            // subduxes
            state = R.merge(
                state,
                R.mapValues(subReducers, (reducer, slice) =>
                    (reducer as any)(state[slice], action),
                ),
            );
        }

        return state;
    };

    return reducer;

    /*
            if (subReducers) {
                if (subduxes['*']) {
                    newState = u.updateIn(
                        '*',
                        subduxes['*'].upreducer(action),
                        newState,
                    );
                } else {
                    const update = mapValues(subReducers, (upReducer) =>
                        upReducer(action),
                    );
    
                    newState = u(update, newState);
                }
            }
    
            const a = mutations[action.type] || mutations['+'];
    
            if (!a) return newState;
    
            return a(action.payload, action)(newState);
        };
    
        return wrapper ? wrapper(upreducer) : upreducer;
            */
}