boonya/react-hook-form-validation

import { FieldRule, Condition, FormPayload, FieldState } from '../types';
import validateValue from '../validators';
import { extractFieldValue } from '../helpers';

function isConditionMet(condition: Condition, payload: FormPayload, index: number): boolean {
    const [selector, ...fields] = condition;
    const values = fields.map((name) => extractFieldValue(payload, name, index));
    return selector(...values);
}

type ReducerResult = Promise<FieldState | null>;

export default function validityReducerCreator(payload: FormPayload, name: string, value: unknown, index: number) {
    return async (acc: ReducerResult, rule: FieldRule): ReducerResult => {
        const state = await acc;

        if (state && state.error) {
            return acc;
        }

        const { validator, condition, ...props } = rule;

        if (condition && isConditionMet(condition, payload, index) === false) {
            return null;
        }

        const { error, message } = await validateValue(validator, value, props);

        return {
            name,
            index,
            pristine: value === undefined,
            error,
            message,
        };
    };
}