const fs = require('fs')

module.exports = function(app, conf) {
  app.use(async (ctx, next) => {
    await next() 
    if (ctx.path === '/') {
      let html = await handleDict(ctx.body)
      ctx.body = html
    }
  })
}

function handleDict (buffer) {
  return new Promise((resolve, reject) => {
    let rawHTML = ''
    if (buffer instanceof Buffer) {
      rawHTML = replacePlaceholder(buffer.toString('utf-8'))
      resolve(rawHTML)
    } else {
      buffer.on('data', data => rawHTML += replacePlaceholder(data.toString()))
      buffer.on('end', data => resolve(rawHTML))
      buffer.on('error', e => reject(e))
    }
  });
}

function replacePlaceholder (str) {
  return str
    .replace('{{version}}', `?version=${ (Math.random() * 1000000).toFixed(0) }`)
    .replace('{{lang}}', 'zh')
}