createReducers.ts

import { Reducer } from "redux";
import { Dispatch } from "react-redux";

export type ReducerCur<TState, TPayload = any> = (payloyoad: TPayload) => (state: TState) => TState;

export type ActionCreator<TPayload> = (payload: TPayload) => ({ type: string } & TPayload);
type GetActionCreator<TState, T> = T extends ReducerCur<TState, infer TPayload> ? ActionCreator<TPayload> : void;
export type ActionCreatorsSet<TState, T> = { [TName in keyof T]: GetActionCreator<TState, T[TName]> };

export interface Bundle<TState, TReducersSet> {
    reducer: Reducer<TState, any>;
    actionCreators: ActionCreatorsSet<TState, TReducersSet>;
    bind(dispatch: Dispatch<TState>): ActionCreatorsSet<TState, TReducersSet>;
}

export interface BuildReducerOptions {
    prefix?: string;
}

export function buildReducer<TState, TReducersSet>(
    initialState: TState,
    reducersSet: TReducersSet,
    options?: BuildReducerOptions
): Bundle<TState, TReducersSet> {
    const effectiveOptions: BuildReducerOptions = options || {};
    const reducers: Record<string, ReducerCur<TState>> = {};
    const actionCreators: any = {};
    const actionDispatchers: any = {};

    Object.keys(reducersSet).forEach((name: string) => {
        let type = name.replace(/(?:^|\.?)([A-Z])/g, (x, y) => { return "_" + y.toLowerCase(); }).replace(/^_/, "").toUpperCase();
        if (effectiveOptions.prefix) {
            type = effectiveOptions.prefix + '_' + type;
        }
        reducers[type] = (reducersSet as any)[name];
        actionCreators[name] = (payload: any) => ({ type, ...payload });
        actionDispatchers[name] = (dispatch: Dispatch<TState>) => (payload: any) => dispatch({ ...payload, type });        
    });

    function reducer(state: any, action: any) {
        if (typeof state === 'undefined') {
            return initialState;
        }

        const reducerCar: ReducerCur<any, any> = (reducers as any)[action.type];
        const newState = reducerCar ? reducerCar(action)(state) : state;
        return newState;
    }

    function bind(dispatch: Dispatch<TState>) {
        const actionEmitters: any = {};
        Object.keys(actionDispatchers).forEach(key => actionEmitters[key] = actionDispatchers[key](dispatch));
        return actionEmitters;
    }

    return { reducer, actionCreators, bind };
}