phoi_Select only mono items on selected tracks.lua

-- USER VARIABLES
local chanTarget = 1 -- number of channels of items that should be selected

-- NAME
local scriptName = ({reaper. get_action_context()})[2]:match("([^/\\]+)%.lua$") -- generate default scriptName from file

--FUNCTIONS FOR DEBUG
local function msg(s)
    reaper.ShowConsoleMsg(tostring(s) .. "\n")
end

--- FUNCTIONS

local function unselectAllItems ()
    while (reaper.CountSelectedMediaItems(0) > 0) do
        reaper.SetMediaItemSelected(reaper.GetSelectedMediaItem(0, 0), false)
    end
end

local function setItemsSelected (itemsT, unselectOthers) -- zero-indexed table of items as input
    if unselectOthers then unselectAllItems() end

    for i = 0, #itemsT do
        local item = itemsT[i]
        if reaper.ValidatePtr(item, "MediaItem*") then
            reaper.SetMediaItemSelected(item, true)
        end
    end
end

----- END OF FUNCTIONS

function main()
    reaper.Undo_BeginBlock()
    local targetItems = {}
    local x = 0
    for i = 0, reaper.CountSelectedTracks(0) - 1 do
        local tr = reaper.GetSelectedTrack(0, i)
        for j = 0, reaper.CountTrackMediaItems(tr) - 1 do
            local it = reaper.GetTrackMediaItem(tr, j)
            local tk = reaper.GetActiveTake(it)
            if tk then
                local src = reaper.GetMediaItemTake_Source(tk)
                local srcChans = reaper.GetMediaSourceNumChannels(src)
                if srcChans == chanTarget then -- add item to table if source channels equal to target
                    targetItems[x] = it
                    x = x + 1
                end
            end
        end
    end
    setItemsSelected(targetItems, true)
    reaper.SetCursorContext( 1, nil ) -- focus arrange
    reaper.Undo_EndBlock(scriptName, -1)
end

reaper.PreventUIRefresh(1)
main()
reaper.PreventUIRefresh(-1)
reaper.UpdateArrange()