// 文件加载工具
/**
 * js加载
 * @param src 文件路径
 * @returns {Promise<>}
 */
export function jsLoading(src) {
  return new Promise((resolve, reject) => {
    try {
      let head = document.getElementsByTagName('head')[0]
      let script = document.createElement('script')
      script.type = 'text/javascript'
      script.src = src + '?t=' + new Date().getTime()
      script.onload = script.onreadystatechange = () => {
        console.log(`[${script.src}] script load ok`)
        resolve()
      }
      head.appendChild(script)
    } catch (e) {
      console.error(e)
      reject()
    }
  })
}


/**
 * css文件加载
 * @param path 文件路径
 * @returns {Promise<>}
 */
export function cssLoading(path) {
  return new Promise((resolve, reject) => {
    try {
      let head = document.getElementsByTagName('head')[0]
      let css = document.createElement('link')
      css.rel = 'stylesheet'
      css.type = 'text/css'
      css.href = path + '?t=' + new Date().getTime()
      css.onload = css.onreadystatechange = () => {
        console.log(`[${css.href}] css load ok`)
        resolve()
      }
      head.appendChild(css)
    } catch (e) {
      console.error(e)
      reject()
    }
  })
}

/**
 * css文件加载
 * @param path 文件路径
 * @returns {Promise<>}
 */
export function lessLoading(path) {
  return new Promise((resolve, reject) => {
    try {
      let head = document.getElementsByTagName('head')[0]
      let css = document.createElement('link')
      css.rel = 'stylesheet/less'
      css.type = 'text/css'
      css.href = path + '?t=' + new Date().getTime()
      css.onload = css.onreadystatechange = () => {
        console.log(`[${path}] css load ok`)
        resolve()
      }
      head.appendChild(css)
    } catch (e) {
      console.error(e)
      reject()
    }
  })
}

/**
 * html代码压缩
 * @param htmlStr
 * @returns {string}
 */
export function htmlCompress(htmlStr) {
  // 字符串转换成文档类型
  let domParser = new DOMParser()
  let doc = domParser.parseFromString(htmlStr, 'text/html')

  // 使用原生的TreeWalker进行遍历
  let treeWalker = document.createTreeWalker(doc)
  let arrNodeRemove = []
  // 遍历注释节点和换行文本节点
  while (treeWalker.nextNode()) {
    let node = treeWalker.currentNode
    if (node.nodeType === Node.COMMENT_NODE || (node.nodeType === Node.TEXT_NODE && node.nodeValue.trim() === '')) {
      arrNodeRemove.push(node)
    }
  }
  // 节点移除
  arrNodeRemove.forEach(function (node) {
    node.parentNode.removeChild(node)
  })

  return doc.body.innerHTML
}

export default Object.freeze(window.FileUtil = {
  jsLoading,
  cssLoading,
  lessLoading,
  htmlCompress
})