const path = require('path')
const sharp =  require('sharp');
const sharp1 =  require('sharp');

const getSlide = async () => {
  const width = 334
  const height = 140
  const fragmentSize = 35
  try {
    // 随机选择某个图片
    const filePath = getRandomPath()
    //随机选择空缺部分的x y 坐标
    const x = (Math.floor(Math.random() * 1000) % (width - 2 * fragmentSize)) + fragmentSize
    const y = Math.floor(Math.random() * 1000) % (height - fragmentSize)
    //获得大小图
    const { image, fragment } = await createImage(filePath, width, height, fragmentSize, x, y)
    console.log(image,fragment)
    return { success: true, data: { image, fragment, x, y } }
  } catch (err) {
    return {success: false,  msg: "服务器错误:" + err, data: null }
  }
}

function getRandomPath() {
  const fileLength = 2
  const index = Math.floor(Math.random() * 1000) % fileLength
  return path.resolve(__dirname, `../static/images/${index + 1}.jpg`)
}

// 生成大图和小图,返回base64
function createImage(filePath, w, h, s, x, y) {
  return new Promise((resolve, reject) => {
    const res = {image: "", fragment: ""}
    const bg = `C:/Users/64616/WebstormProjects/验证码/koa/static/images/bg.jpg`

    sharp(filePath)
        .resize(w, h, "!")//调整成统一尺寸
        .extract({left: x, top: y, width: s, height: s})//截取小图
        .toBuffer()
        .then(imageData => {
          let data = imageData.toString('base64');//转换成base64的形式
          res.fragment = "data:image/jpg;base64," + data

          sharp1(filePath).resize(w, h, "!")
              .composite([{input: bg, top: y, left: x, raw: {width: s, height: s, channels: 1}}])
              //把与小图部分大小相同的灰色图片覆盖在大图上，形成大图空缺的样子
              .toBuffer()
              .then(imageData => {
                let data = imageData.toString('base64');
                res.image = "data:image/jpg;base64," + data
                resolve(res)//返回结果
              })
              .catch(error => {
                throw(error)
              })
        })
        .catch(error => {
          throw(error)
        })
  })
}


module.exports = {
  getSlide,
  check,
}