const namespace = 'ui'
const statePrefix = 'is-'

function _bem(namespace: string, block: string, blockSuffix: string, element: string, modifier: string) {
  let cls = `${block}`
  if (blockSuffix)
    cls += `-${blockSuffix}`

  if (element)
    cls += `__${element}`

  if (modifier)
    cls += `--${modifier}`

  return cls
}

export default (block: string) => {
  const b = (blockSuffix: string = '') => _bem(namespace, block, blockSuffix, '', '')
  const e = (element: string) =>
    element ? _bem(namespace, block, '', element, '') : ''
  const m = (modifier: string) =>
    modifier ? _bem(namespace, block, '', '', modifier) : ''
  const be = (blockSuffix: string, element: string) =>
    blockSuffix && element
      ? _bem(namespace, block, blockSuffix, element, '')
      : ''
  const em = (element: string, modifier: string) =>
    element && modifier ? _bem(namespace, block, '', element, modifier) : ''
  const bm = (blockSuffix: string, modifier: string) =>
    blockSuffix && modifier
      ? _bem(namespace, block, blockSuffix, '', modifier)
      : ''
  const bem = (blockSuffix: string, element: string, modifier: string) =>
    blockSuffix && element && modifier
      ? _bem(namespace, block, blockSuffix, element, modifier)
      : ''
  const is = (name: string, ...args: any[]) => {
    const state = args.length >= 1 ? args[0] : true
    return name && state ? `${statePrefix}${name}` : ''
  }
  const has = (name: string, ...args: any[]) => {
    const state = args.length >= 1 ? args[0] : true
    return name && state ? `has-${name}` : ''
  }
  const exp = (condition: boolean, trueState: string, falseState: string = '') => {
    return condition ? trueState : falseState
  }

  return {
    namespace,
    b,
    e,
    m,
    be,
    em,
    bm,
    bem,
    is,
    has,
    exp,
  }
}