// @flow
import type { TimingFunction } from '../types/timingFunction'

const functionsMap = {
  back: 'cubic-bezier(0.600, -0.280, 0.735, 0.045)',
  circ: 'cubic-bezier(0.600,  0.040, 0.980, 0.335)',
  cubic: 'cubic-bezier(0.550,  0.055, 0.675, 0.190)',
  expo: 'cubic-bezier(0.950,  0.050, 0.795, 0.035)',
  quad: 'cubic-bezier(0.550,  0.085, 0.680, 0.530)',
  quart: 'cubic-bezier(0.895,  0.030, 0.685, 0.220)',
  quint: 'cubic-bezier(0.755,  0.050, 0.855, 0.060)',
  sine: 'cubic-bezier(0.470,  0.000, 0.745, 0.715)',
}

/**
 * String to represent common easing functions as demonstrated here: (github.com/jaukia/easie).
 *
 * @example
 * // Styles as object usage
 * const styles = {
 *   'transitionTimingFunction': easeIn('quad')
 * }
 *
 * // styled-components usage
 *  const div = styled.div`
 *   transitionTimingFunction: ${easeIn('quad')};
 * `
 *
 * // CSS as JS Output
 *
 * 'div': {
 *   'transitionTimingFunction': 'cubic-bezier(0.550,  0.085, 0.680, 0.530)',
 * }
 */
export default function easeIn(functionName: string): TimingFunction {
  return functionsMap[functionName.toLowerCase().trim()]
}