source_utils_probedStreams.bs

' A source the server has never probed (a .strm item before its first play) lists no media streams,
' so a track pick made from it has nothing to choose from. The PlaybackInfo that starts the play
' probes the source, and the server saves what it found.
import "pkg:/source/enums/UpstreamManifestBlocker.bs"
import "pkg:/source/utils/misc.bs"

' True when the source exists and lists no media streams yet.
'
' @param {dynamic} source - a MediaSourceInfo
' @returns {boolean}
function sourceListsNoStreams(source as dynamic) as boolean
  if not isValid(source) then return false
  return not isValidAndNotEmpty(source.MediaStreams)
end function

' The audio stream index the server built its transcode for: the AudioStreamIndex in the
' TranscodingUrl, else the source's DefaultAudioStreamIndex, else -1.
'
' @param {dynamic} source - a MediaSourceInfo from a PlaybackInfo answer
' @returns {integer}
function serverAudioIndex(source as dynamic) as integer
  if not isValid(source) then return -1
  match = CreateObject("roRegex", "[?&]AudioStreamIndex=(-?[0-9]+)", "i").Match(textOrEmpty(source.TranscodingUrl))
  if match.count() > 1 then return match[1].toInt()
  if isValid(source.DefaultAudioStreamIndex) then return source.DefaultAudioStreamIndex
  return -1
end function

' True when the server's answer is the stream that plays, so the track picks it was built with
' matter. The device plays the source's own manifest URL when nothing blocks it and the device can
' load it; when it cannot but the server allowed direct play, the player's retry asks the server
' again with our picks (retryPlayback). Only a blocker, or a URL the device cannot load and the
' server refused, leaves the answer as it is.
'
' @param {string} blocker - an UpstreamManifestBlocker value for the source
' @param {boolean} deviceLoadsUpstream - the device's check that it can load the manifest URL
' @param {boolean} serverAllowed - the answer's SupportsDirectPlay
' @returns {boolean}
function serverAnswerPlays(blocker as string, deviceLoadsUpstream as boolean, serverAllowed as boolean) as boolean
  if blocker <> UpstreamManifestBlocker.NONE then return true
  return not deviceLoadsUpstream and not serverAllowed
end function

' True when picks made from the probed streams differ from what a transcode answer was built
' with, so that answer has to be asked for again. A direct play answer never does: the device
' plays the source itself and switches tracks on its own.
'
' @param {dynamic} answerSource - the MediaSourceInfo the PlaybackInfo answer returned
' @param {integer} audioIndex - the audio index picked from the probed streams
' @param {integer} subtitleIndex - the subtitle index picked from the probed streams
' @param {integer} sentSubtitleIndex - the subtitle index the answered request carried
' @returns {boolean}
function probedPicksNeedNewAnswer(answerSource as dynamic, audioIndex as integer, subtitleIndex as integer, sentSubtitleIndex as integer) as boolean
  if not isValid(answerSource) or not isValidAndNotEmpty(answerSource.TranscodingUrl) then return false
  if audioIndex >= 0 and audioIndex <> serverAudioIndex(answerSource) then return true
  return subtitleIndex <> sentSubtitleIndex
end function