/**

* bem helper

* b() // 'button'

* b('text') // 'button__text'

* b({ disabled }) // 'button button--disabled'

* b('text', { disabled }) // 'button__text button__text--disabled'

* b(['disabled', 'primary']) // 'button button--disabled button--primary'

*/

export type Mod = string | { [key: string]: any };

export type Mods = Mod | Mod[];

const ELEMENT = '__';

const MODS = '--';

function join(name: string, el?: string, symbol?: string): string {

return el ? name + symbol + el : name;

}

function prefix(name: string, mods: Mods): Mods {

if (typeof mods === 'string') {

return join(name, mods, MODS);

}

if (Array.isArray(mods)) {

return mods.map(item => <Mod>prefix(name, item));

}

const ret: Mods = {};

if (mods) {

Object.keys(mods).forEach(key => {

ret[name + MODS + key] = mods[key];

});

}

return ret;

}

export function createBEM(name: string) {

return function(el?: Mods, mods?: Mods): Mods {

if (el && typeof el !== 'string') {

mods = el;

el = '';

}

el = join(name, el, ELEMENT);

return mods ? [el, prefix(el, mods)] : el;

};

}

export type BEM = ReturnType<typeof createBEM>;