export type Action<T extends string = string, TPayload = any> = {
    type: T;
    meta?: Record<string, unknown>;
    payload?: TPayload;
};

export type ActionGenerator<
    TType extends string = string,
    TPayloadGen = (...args: any[]) => any,
> = {
    type: TType;
} & (TPayloadGen extends (...args: any) => any
    ? ReturnType<TPayloadGen> extends void
        ? (...args: Parameters<TPayloadGen>) => {
              type: TType;
          }
        : (...args: Parameters<TPayloadGen>) => {
              type: TType;
              payload: ReturnType<TPayloadGen>;
          }
    : (...args: any[]) => { type: TType; payload?: unknown });

export function action<
    TType extends string,
    TPayload extends (...args: any) => any,
>(
    type: TType,
    payloadFunction?: TPayload,
    transformer?: Function,
): ActionGenerator<TType, TPayload> {
    let generator: any = function (...payloadArg:any[]) {
        const result: Action = { type };

        if (payloadFunction) {
            result.payload = payloadFunction(...payloadArg);
        } else {
            if (payloadArg[0] !== undefined) result.payload = payloadArg[0];
        }

        return result;
    };

    if (transformer) {
        const orig = generator;
        generator = (...args: any) => transformer(orig(...args), args);
    }

    generator.type = type;

    return generator;
}