reaper_dir_scan.lua

local function getPathDelimiter()
    local os = reaper.GetOS()
    if os == 'Win32' or os == 'Win64' then
        return '\\'
    else
        return '/'
    end
end
local PD = getPathDelimiter()

function get_dir_folders(dir_path)
    local folders = {}
    local i = 0
    while true do
        local folder_name = reaper.EnumerateSubdirectories(dir_path, i)
        if not folder_name then break end
        local folder_path = dir_path .. PD .. folder_name
        table.insert(folders, folder_path)
        i = i + 1
    end
    return folders
end

function get_dir_files(dir_path)
    local files = {}
    local i = 0
    while true do
        local file_name = reaper.EnumerateFiles(dir_path, i)
        if not file_name then break end
        local file_path = dir_path .. PD .. file_name
        table.insert(files, file_path)
        i = i + 1
    end
    return files
end