import { getString, getNumber } from './util'

export interface HighlightArgs {
  /**
   * Highlight color. Default `'red'`.
   */
  color?: string
  /**
   * Highlight blur. Default `0`.
   */
  blur?: number
  /**
   * Highlight width. Default `1`.
   */
  width?: number
  /**
   * Highlight opacity. Default `1`.
   */
  opacity?: number
}

export function highlight(args: HighlightArgs = {}) {
  const color = getString(args.color, 'red')
  const blur = getNumber(args.blur, 0)
  const width = getNumber(args.width, 1)
  const opacity = getNumber(args.opacity, 1)

  return `
      <filter>
        <feFlood flood-color="${color}" flood-opacity="${opacity}" result="colored"/>
        <feMorphology result="morphed" in="SourceGraphic" operator="dilate" radius="${width}"/>
        <feComposite result="composed" in="colored" in2="morphed" operator="in"/>
        <feGaussianBlur result="blured" in="composed" stdDeviation="${blur}"/>
        <feBlend in="SourceGraphic" in2="blured" mode="normal"/>
      </filter>
    `.trim()
}