import {type TextStyle} from 'react-native'

import {isWeb} from '../platform'
import * as tokens from '../tokens'

/**
 * Util to calculate lineHeight from a text size atom and a leading atom (which
 * are unitless). On native, this will evaluate to a rounded pixel value. On
 * web, it will be a unitless string.
 *
 * Example:
 *   `leading({
 *     fontSize: 15,
 *     lineHeight: 1.2
 *   })` // => { lineHeight: 17 }
 */
export function leading(textStyle: TextStyle): Pick<TextStyle, 'lineHeight'> {
  const lineHeight = textStyle?.lineHeight || tokens.lineHeight.snug

  if (isWeb) {
    return {
      lineHeight: String(lineHeight) as unknown as TextStyle['lineHeight'],
    }
  } else {
    const size = textStyle?.fontSize || tokens.fontSize.sm
    return {
      lineHeight: Math.round(size * lineHeight),
    }
  }
}