if not modules then modules = { } end modules ['node-shp'] = {
    version   = 1.001,
    optimize  = true,
    comment   = "companion to node-ini.mkiv",
    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "see context related readme files"
}

local next, type = next, type
local format = string.format
local setmetatableindex = table.setmetatableindex

local nodes        = nodes
local tasks        = nodes.tasks
local handlers     = nodes.handlers

local nodecodes    = nodes.nodecodes
local hlist_code   = nodecodes.hlist
local vlist_code   = nodecodes.vlist

local nuts         = nodes.nuts
local tonut        = nuts.tonut

local nextnode     = nuts.traversers.node
local getlist      = nuts.getlist
local getbox       = nuts.getbox

local implement    = interfaces.implement

local actions = tasks.actions("shipouts")

function handlers.finalizebox(box)
    actions(getbox(box)) -- nut
end

handlers.cleanuppage = nuts.flatten_discretionaries

-- interface

implement {
    name      = "finalizebox",
    arguments = "integer",
    actions   = handlers.finalizebox,
}

-- just in case we want to optimize lookups:

local frequencies = { }

nodes.tracers.frequencies = frequencies

local data = { }
local done = false

setmetatableindex(data,function(t,k)
    local v = { }
    setmetatableindex(v,function(t,k)
        local v = { }
        t[k] = v
        setmetatableindex(v,function(t,k)
            t[k] = 0
            return 0
        end)
        return v
    end)
    t[k] = v
    return v
end)

local function count(head,data,subcategory)
    -- no components, pre, post, replace .. can maybe an option .. but
    -- we use this for optimization so it makes sense to look the the
    -- main node only
    for n, id in nextnode, tonut(head) do
        local dn = data[nodecodes[id]] -- we could use id and then later convert to nodecodes
        dn[subcategory] = dn[subcategory] + 1
        if id == hlist_code or id == vlist_code then
            count(getlist(n),data,subcategory)
        end
    end
end

local function register(category,subcategory)
    return function(head)
        done = true
        count(head,data[category],subcategory)
        return head, false
    end
end

frequencies.register = register
frequencies.filename = nil

trackers.register("nodes.frequencies",function(v)
    if type(v) == "string" then
        frequencies.filename = v
    end
    handlers.frequencies_shipouts_before   = register("shipouts",   "begin")
    handlers.frequencies_shipouts_after    = register("shipouts",   "end")
    handlers.frequencies_processors_before = register("processors", "begin")
    handlers.frequencies_processors_after  = register("processors", "end")
    tasks.prependaction("shipouts",   "before", "nodes.handlers.frequencies_shipouts_before")
    tasks.appendaction ("shipouts",   "after",  "nodes.handlers.frequencies_shipouts_after")
    tasks.prependaction("processors", "before", "nodes.handlers.frequencies_processors_before")
    tasks.appendaction ("processors", "after",  "nodes.handlers.frequencies_processors_after")
end)

statistics.register("node frequencies", function()
    if done then
        local filename = frequencies.filename or (tex.jobname .. "-frequencies.lua")
        io.savedata(filename,table.serialize(data,true))
        return format("saved in %q",filename)
    end
end)