var path = require('path')
var glob = require('glob');
var config = require('../config')
var ExtractTextPlugin = require('extract-text-webpack-plugin')
var HtmlWebpackPlugin = require('html-webpack-plugin')

exports.assetsPath = function (_path) {
  var assetsSubDirectory = process.env.NODE_ENV === 'production'
    ? config.build.assetsSubDirectory
    : config.dev.assetsSubDirectory
  return path.posix.join(assetsSubDirectory, _path)
}

exports.cssLoaders = function (options) {
  options = options || {}

  var cssLoader = {
    loader: 'css-loader',
    options: {
      minimize: process.env.NODE_ENV === 'production',
      sourceMap: options.sourceMap
    }
  }

  // generate loader string to be used with extract text plugin
  function generateLoaders (loader, loaderOptions) {
    var loaders = [cssLoader]
    if (loader) {
      loaders.push({
        loader: loader + '-loader',
        options: Object.assign({}, loaderOptions, {
          sourceMap: options.sourceMap
        })
      })
    }

    // Extract CSS when that option is specified
    // (which is the case during production build)
    if (options.extract) {
      return ExtractTextPlugin.extract({
        use: loaders,
        fallback: 'vue-style-loader',
        publicPath: '../../'
      })
    } else {
      return ['vue-style-loader'].concat(loaders)
    }
  }

  // https://vue-loader.vuejs.org/en/configurations/extract-css.html
  return {
    css: generateLoaders(),
    postcss: generateLoaders(),
    less: generateLoaders('less'),
    sass: generateLoaders('sass', { indentedSyntax: true }),
    scss: generateLoaders('sass'),
    stylus: generateLoaders('stylus'),
    styl: generateLoaders('stylus')
  }
}

// Generate loaders for standalone style files (outside of .vue)
exports.styleLoaders = function (options) {
  var output = []
  var loaders = exports.cssLoaders(options)
  for (var extension in loaders) {
    var loader = loaders[extension]
    output.push({
      test: new RegExp('\\.' + extension + '$'),
      use: loader
    })
  }
  return output
}

exports.getEntries = function (globPath) {
  var entries = {}
  /**
   * 读取src目录,并进行路径裁剪
   */
  glob.sync(globPath).forEach(function (entry) {
    /**
     * path.basename 提取出用 ‘/' 隔开的path的最后一部分，除第一个参数外其余是需要过滤的字符串
     * path.extname 获取文件后缀
     */
    // var basename = path.basename(entry, path.extname(entry), 'router.js') // 过滤router.js
    // ***************begin***************
    // 当然， 你也可以加上模块名称, 即输出如下： { module/main: './src/module/index/main.js', module/test: './src/module/test/test.js' }
    // 最终编译输出的文件也在module目录下， 访问路径需要时 localhost:8080/module/index.html
    // slice 从已有的数组中返回选定的元素, -3 倒序选择，即选择最后三个
    var tmp = entry.split('/').splice(-3)
    var moduleName = tmp.slice(1, 2);
    // ***************end***************
    entries[moduleName] = entry
  });
  //console.log(entries);
  // 获取的主入口如下： { main: './src/module/index/main.js', test: './src/module/test/test.js' }
  return entries;
}

// generate dist index.html with correct asset hash for caching.
// you can customize output by editing /index.html
// see https://github.com/ampedandwired/html-webpack-plugin
exports.getHtmlWebpackPlugins = function () {
  var pages = this.getEntries('./src/module/**/*.html')
  var htmlWebpackPlugins = []
  for (var page in pages) {
    // 配置生成的html文件，定义路径等
    var conf = {
      filename: page + '.html',
      template: pages[page], //模板路径
      inject: true,
      // excludeChunks 允许跳过某些chunks, 而chunks告诉插件要引用entry里面的哪几个入口
      // 如何更确定理解这块呢？举个例子：比如本demo中包含两个模块（index和about），最确定当然是各个模块引入自己所需的js，
      // 而不是每个页面都引入所有的js，你可以把下面这个excludeChunks去掉，然后npm run build，然后看编译出来的index.html和about.html就知道了
      // filter：将数据过滤，然后返回符合要求的数据，Object.keys是获取JSON对象中的每个key
      excludeChunks: Object.keys(pages).filter(item => {
        return (item != page)
      }),
      minify: {
        removeComments: true,
        collapseWhitespace: true,
        removeAttributeQuotes: true
        // more options:
        // https://github.com/kangax/html-minifier#options-quick-reference
      },
      // necessary to consistently work with multiple chunks via CommonsChunkPlugin
      chunksSortMode: 'dependency',
      // chunks: ['manifest', 'vendors', page], // 每个html引用的js模块
    }
    htmlWebpackPlugins.push(new HtmlWebpackPlugin(conf))
  }
  return htmlWebpackPlugins
}