/**
 * 颜色工具类
 * @author zhongming
 */
export default class ColorUtil {

  // 默认的深色/浅色阈值
  private static defaultThreshold: number = 192

  /**
   * 将十六进制颜色代码转为RGB
   * @param colorCode 十六进制颜色代码
   */
  public static convertHexadecimalToRGB (colorCode: string): Array<number> | null {
    if (colorCode.substr(0, 1) === '#') {
      colorCode = colorCode.substring(1)
    }
    if (colorCode.length !== 6) {
      console.error('请输入正确的十六进制颜色代码')
    } else {
      colorCode = colorCode.toLowerCase()
      const b: Array<string> = []
      for (let x = 0; x < 3; x++) {
        b[0] = colorCode.substr(x * 2, 2)
        b[3] = '0123456789abcdef'
        b[1] = b[0].substr(0, 1)
        b[2] = b[0].substr(1, 1)
        b[20 + x] = (b[3].indexOf(b[1]) * 16 + b[3].indexOf(b[2])) + ''
      }
      return [parseInt(b[20]), parseInt(b[21]), parseInt(b[22])]
    }
    return null
  }

  /**
   * 将RGB转为十六进制颜色代码
   * @param rgb rgb颜色
   */
  public static convertRGBToHexadecimal(rgb: Array<number>): string | null {
    if (rgb.length !== 3) {
      console.error('参数错误，RGB长度必须为3，实际参数：', rgb)
    } else {
      const r = rgb[0]
      const g = rgb[1]
      const b = rgb[2]
      return ((r << 16) | (g << 8) | b).toString(16)
    }
    return null
  }

  /**
   * 判断颜色是否为深色
   * @param colorCode 颜色
   * @param threshold 阈值
   */
  public static isDark (colorCode: any, threshold?: number): boolean | null {
    if (!threshold) {
      threshold = this.defaultThreshold
    }
    let rgb: number[] | null = null
    if (colorCode instanceof Array) {
      rgb = colorCode
    } else if (typeof(colorCode) === 'string') {
      rgb = this.convertHexadecimalToRGB(colorCode)
    }
    if (rgb !== null) {
      const r = rgb[0]
      const g = rgb[1]
      const b = rgb[2]
      return (r*0.299 + g*0.578 + b*0.114) < threshold
    }
    return null
  }

  public static isDark1 (r: number, g: number, b: number, threshold: number): boolean {
    return (r*0.299 + g*0.578 + b*0.114) < threshold
  }
}