import { useMemo } from 'react';

import { ClassNameProp } from '../types';

type useBemModifiers = Record<string, boolean | string | undefined>;

interface useBemProps {
  block: string;
  element?: string;
  modifiers?: useBemModifiers;
  className?: ClassNameProp<any>;
}

// Generate className following BEM methodology: http://getbem.com/naming/
// Modifier value can be one of the following types: boolean, string, undefined
export const useBEM = ({ block, element, modifiers, className }: useBemProps) =>
  useMemo(() => {
    const blockElement = element ? `${block}__${element}` : block;

    let classString = blockElement;
    modifiers &&
      Object.keys(modifiers).forEach((name) => {
        const value = modifiers[name];
        if (value) classString += ` ${blockElement}--${value === true ? name : `${name}-${value}`}`;
      });

    let expandedClassName = typeof className === 'function' ? className(modifiers) : className;
    if (typeof expandedClassName === 'string') {
      expandedClassName = expandedClassName.trim();
      if (expandedClassName) classString += ` ${expandedClassName}`;
    }

    return classString;
  }, [block, element, modifiers, className]);