cfillion_Select destination tracks of selected tracks sends recursively.lua

-- @description Select destination tracks of selected tracks sends recursively
-- @author cfillion
-- @version 1.2.1
-- @changelog Fix crash when encountering feedback routings
-- @provides [main] . > cfillion_Select destination tracks of selected tracks sends recursively (background).lua
-- @link Forum thread https://forum.cockos.com/showthread.php?t=183638
-- @donation https://www.paypal.me/cfillion

-- This file is also used by cfillion_Select source tracks of selected tracks sends recursively.lua

local scriptName = ({reaper.get_action_context()})[2]:match("([^/\\_]+).lua$")
local background = scriptName:match("background")
local destination = scriptName:match("destination")

local selected = {}

local function inArray(haystack, match)
  for i,item in ipairs(haystack) do
    if item == match then
      return true
    end
  end

  return false
end

local function enumSendTracks(track)
  local sendReceive = destination and 0 or -1
  local trackType = destination and 1 or 0
  local i, max = -1, reaper.GetTrackNumSends(track, sendReceive) - 1

  return function()
    while i < max do
      i = i + 1

      local muted = reaper.GetTrackSendInfo_Value(track, sendReceive, i, 'B_MUTE') == 1

      if not muted then
        return reaper.BR_GetMediaTrackSendInfo_Track(
          track, sendReceive, i, trackType)
      end
    end
  end
end

local function enumDirectChildTracks(track)
  local index = reaper.GetMediaTrackInfo_Value(track, 'IP_TRACKNUMBER')
  local depth = reaper.GetMediaTrackInfo_Value(track, 'I_FOLDERDEPTH')
  local count = reaper.CountTracks(0)

  return function()
    while depth > 0 and index < count do
      track = reaper.GetTrack(0, index)

      local direct = depth == 1
      local parentSend = reaper.GetMediaTrackInfo_Value(track, 'B_MAINSEND') == 1

      index = index + 1
      depth = depth + reaper.GetMediaTrackInfo_Value(track, 'I_FOLDERDEPTH')

      if direct and parentSend then
        return track
      end
    end
  end
end

local function highlight(track, select, seenTracks)
  if not seenTracks then seenTracks = {} end
  if inArray(seenTracks, track) then return end
  table.insert(seenTracks, track)

  for target in enumSendTracks(track) do
    reaper.SetTrackSelected(target, select)

    if select then
      highlight(target, select, seenTracks)
    end
  end

  if destination then
    local parentSend = reaper.GetMediaTrackInfo_Value(track, 'B_MAINSEND') == 1
    local parent = parentSend and reaper.GetParentTrack(track)
    if parent then
      reaper.SetTrackSelected(parent, select)
      highlight(parent, select, seenTracks)
    end
  else
    for child in enumDirectChildTracks(track) do
      reaper.SetTrackSelected(child, select)
      highlight(child, select, seenTracks)
    end
  end
end

local function main()
  for i=0,reaper.CountSelectedTracks(0)-1 do
    local track = reaper.GetSelectedTrack(0, i)

    if not inArray(selected, track) then
      table.insert(selected, track)
    end
  end

  for i,track in ipairs(selected) do
    local valid = reaper.ValidatePtr(track, 'MediaTrack*')
    local isSelected = valid and reaper.IsTrackSelected(track)

    if isSelected then
      highlight(track, true)
    else
      -- background mode: unselect destination of unselected tracks
      table.remove(selected, i)

      if valid then
        highlight(track, false)
      end
    end
  end

  reaper.defer(background and main or function() end)
end

main()