/**
 * color转rgb 获取颜色rgb值 用于计算
 * @param {string} hexcolor
 * @return {Array} rgb颜色值 数组
 */
const colorToRgb = hexcolor => {
    let r
    let g
    let b
    if (hexcolor.substr(0, 3) === 'rgb') {
      const start = hexcolor.indexOf('(') + 1
      const length = hexcolor.indexOf(')') - start
      const rgb = hexcolor.substr(start, length).split(',')
      r = parseInt(rgb[0])
      g = parseInt(rgb[1])
      b = parseInt(rgb[2])
    } else {
      hexcolor = hexcolor.substr(0, 1) === '#' ? hexcolor.substr(1) : hexcolor
      if (hexcolor.length === 3) {
        const rgb = hexcolor.split('')
        hexcolor = `${rgb[0]}${rgb[0]}${rgb[1]}${rgb[1]}${rgb[2]}${rgb[2]}`
      }
      r = parseInt(hexcolor.substr(0, 2), 16)
      g = parseInt(hexcolor.substr(2, 2), 16)
      b = parseInt(hexcolor.substr(4, 2), 16)
    }
    return [r, g, b]
  }
  
  /**
   * 颜色减淡
   * @param {string} color hex颜色值
   * @param {number} level 0-1
   * @return {string} rgb颜色值
   */
  const colorLighten = (color, level = 1) => {
    const rgb = colorToRgb(color)
    for (let i = 0; i < 3; i++) {
      rgb[i] = Math.floor((255 - rgb[i]) * level + rgb[i])
    }
    return `rgb(${rgb.join(',')})`
  }
  
  /**
   * 颜色加深
   * @param {string} color hex颜色值
   * @param {number} level 0-1
   * @return {string} rgb颜色值
   */
  const colorDark = (color, level = 1) => {
    const rgb = colorToRgb(color)
    for (let i = 0; i < 3; i++) {
      rgb[i] = Math.floor(rgb[i] * (1 - level))
    }
    return `rgb(${rgb.join(',')})`
  }
  
  /**
   * 计算出具有较高对比度的颜色是白色还是黑色
   * @param {string} hexcolor hex颜色 或者rgb颜色
   * 传入一个hex颜色值会自动对比用这个颜色做为背景，文字应该用白色还是黑色
   */
  const getContrastYIQ = hexcolor => {
    let yiq
    const [r, g, b] = colorToRgb(hexcolor)
    yiq = ((r * 299) + (g * 587) + (b * 114)) / 1000
    return (yiq >= 128) ? 'black' : 'white'
  }
  
  /**
   * 验证是否是合法的颜色值
   * @param {string} color 颜色值
   */
  const isColorString = color => {
    const re1 = /^#([0-9a-f]{6}|[0-9a-f]{3})$/i
    const re2 = /^rgb\(([0-9]|[0-9][0-9]|25[0-5]|2[0-4][0-9]|[0-1][0-9][0-9])\,([0-9]|[0-9][0-9]|25[0-5]|2[0-4][0-9]|[0-1][0-9][0-9])\,([0-9]|[0-9][0-9]|25[0-5]|2[0-4][0-9]|[0-1][0-9][0-9])\)$/i
    const re3 = /^rgba\(([0-9]|[0-9][0-9]|25[0-5]|2[0-4][0-9]|[0-1][0-9][0-9])\,([0-9]|[0-9][0-9]|25[0-5]|2[0-4][0-9]|[0-1][0-9][0-9])\,([0-9]|[0-9][0-9]|25[0-5]|2[0-4][0-9]|[0-1][0-9][0-9])\,(1|1.0|0.[0-9])\)$/i
    return re2.test(color) || re1.test(color) || re3.test(color);
  }
  
  export {
    colorToRgb,
    colorLighten,
    colorDark,
    getContrastYIQ,
    isColorString
  }