manifest-period@start-resets-from-PT0S.js

// rule for AnyProxy tool (http://anyproxy.io/en/)
// support https://github.com/google/shaka-player/issues/1884 investigation

const moment = require('moment')
const parser = require('xml2json')

module.exports = {
  summary: "manifest-period@start-resets-from-PT0S.js",
  *beforeSendResponse(requestDetail, responseDetail) {
    if (requestDetail.url.includes('.mpd')
      && requestDetail.requestOptions.method === "GET"
      && responseDetail.response.header['Content-Type'] === "application/dash+xml"
      && responseDetail.response.statusCode === 200) {

      let newResponse = Object.assign({}, responseDetail.response)

      let manifestJson = JSON.parse(parser.toJson(newResponse.body.toString(), {reversible: true})),
        rootMPD = manifestJson['MPD'],
        periods = [rootMPD.Period].flat()

      if (rootMPD.type === "static"
        && rootMPD.profiles === "urn:mpeg:dash:profile:isoff-live:2011"
        && periods[0]) {

        let firstPeriodStart = moment.duration(periods[0].start || "PT0S")
        periods.forEach(p => {
          p.start = moment.duration(p.start).subtract(firstPeriodStart).toString()
        })

        newResponse.header['X-Proxy-By'] = `AnyProxy: ${this.summary}`
        newResponse.body = parser.toXml(manifestJson)
      }

      return {
        response: newResponse
      }
    }
  }
}