const path = require('path')

const isWin = /^win/.test(process.platform)

const normalizePath = path => (isWin ? path.replace(/\\/g, '/') : path)

const defaultOptions = {
  limit: -1,
  fallback: {
    loader: 'file-loader',
    options: {
      publicPath (url, resourcePath, context) {
        if (
          process.env.UNI_PLATFORM === 'app-plus' &&
          process.env.UNI_USING_V3
        ) { // app-plus v3 下路径不能以/开头
          return normalizePath(path.relative(process.env.UNI_INPUT_DIR, resourcePath))
        }
        return '/' + normalizePath(path.relative(process.env.UNI_INPUT_DIR, resourcePath))
      },
      outputPath (url, resourcePath, context) {
        return normalizePath(path.relative(process.env.UNI_INPUT_DIR, resourcePath))
      }
    }
  }
}

const inlineLimit =
  process.env.UNI_PLATFORM === 'mp-weixin' ||
  process.env.UNI_PLATFORM === 'mp-qq' ||
  process.env.UNI_PLATFORM === 'mp-toutiao' ||
  process.env.UNI_PLATFORM === 'app-plus' // v2需要base64,v3需要rewriteUrl

// mp-weixin,mp-qq,app-plus 非v3(即：需要base64的平台)
// 将/static/logo.png转换为~@/static/logo.png
// @import,src,background,background-image

const rewriteUrl = inlineLimit ? require('postcss-urlrewrite')({
  imports: true,
  properties: ['src', 'background', 'background-image'],
  rules: [{
    from: /^@\//,
    to: '~@/'
  }, {
    from: /^\/([^/])/,
    to: '~@/$1'
  }]
}) : () => {}

module.exports = {
  loader: 'url-loader',
  options () {
    if (process.env.UNI_PLATFORM === 'h5') {
      // h5平台，不对 url-loader 作调整，默认limit:4096，也不修改file-loader输出路径
      return {}
    }
    if (inlineLimit) {
      return {
        ...defaultOptions,
        limit: process.env.UNI_USING_V3 ? -1 : 40960 // （主要用于background-image）
      }
    }
    return {
      ...defaultOptions
    }
  },
  rewriteUrl
}