if not modules then modules = { } end modules ['node-aux'] = {
    version   = 1.001,
    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"
}

-- todo: n1 .. n2 : __concat metatable

local type, tostring = type, tostring

local nodes, node = nodes, node

local utfvalues          = utf.values

local nodecodes          = nodes.nodecodes

local glyph_code         = nodecodes.glyph
local hlist_code         = nodecodes.hlist
local vlist_code         = nodecodes.vlist
local attributelist_code = nodecodes.attributelist -- temporary
local math_code          = nodecodes.math

local nodepool           = nodes.pool

local new_glue           = nodepool.glue
local new_glyph          = nodepool.glyph

local traverse_nodes     = node.traverse
local traverse_id        = node.traverse_id
local free_node          = node.free
local hpack_nodes        = node.hpack
local unset_attribute    = node.unset_attribute
local first_glyph        = node.first_glyph or node.first_character
local copy_node          = node.copy
local copy_node_list     = node.copy_list
local slide_nodes        = node.slide
local insert_node_after  = node.insert_after
local isnode             = node.is_node

local unsetvalue         = attributes.unsetvalue

local current_font       = font.current

local texgetbox          = tex.getbox

local report_error       = logs.reporter("node-aux:error")

function nodes.repackhlist(list,...)
--~ nodes.showsimplelist(list)
    local temp, b = hpack_nodes(list,...)
    list = temp.list
    temp.list = nil
    free_node(temp)
    return list, b
end

local function set_attributes(head,attr,value)
    for n in traverse_nodes(head) do
        n[attr] = value
        local id = n.id
        if id == hlist_node or id == vlist_node then
            set_attributes(n.list,attr,value)
        end
    end
end

local function set_unset_attributes(head,attr,value)
    for n in traverse_nodes(head) do
        if not n[attr] then
            n[attr] = value
        end
        local id = n.id
        if id == hlist_code or id == vlist_code then
            set_unset_attributes(n.list,attr,value)
        end
    end
end

local function unset_attributes(head,attr)
    for n in traverse_nodes(head) do
        n[attr] = unsetvalue
        local id = n.id
        if id == hlist_code or id == vlist_code then
            unset_attributes(n.list,attr)
        end
    end
end

nodes.setattribute       = node.set_attribute
nodes.getattribute       = node.has_attribute
nodes.unsetattribute     = node.unset_attribute
nodes.has_attribute      = node.has_attribute

nodes.firstglyph         = first_glyph
nodes.setattributes      = set_attributes
nodes.setunsetattributes = set_unset_attributes
nodes.unsetattributes    = unset_attributes

-- function nodes.is_skipable(a,id)  -- skipable nodes at the margins during character protrusion
--     return (
--             id ~= glyph_node
--         or  id == ins_node
--         or  id == mark_node
--         or  id == adjust_node
--         or  id == penalty_node
--         or (id == glue_node    and a.spec.writable)
--         or (id == disc_node    and a.pre == nil and a.post == nil and a.replace == nil)
--         or (id == math_node    and a.surround == 0)
--         or (id == kern_node    and (a.kern == 0 or a.subtype == NORMAL))
--         or (id == hlist_node   and a.width == 0 and a.height == 0 and a.depth == 0 and a.list == nil)
--         or (id == whatsit_node and a.subtype ~= pdf_refximage_node and a.subtype ~= pdf_refxform_node)
--     )
-- end

-- history:
--
--
-- local function glyph_width(a)
--     local ch = chardata[a.font][a.char]
--     return (ch and ch.width) or 0
-- end
--
-- local function glyph_total(a)
--     local ch = chardata[a.font][a.char]
--     return (ch and (ch.height+ch.depth)) or 0
-- end
--
-- local function non_discardable(a) -- inline
--     return a.id < math_node -- brrrr
-- end
--
-- local function calculate_badness(t,s)
--     if t == 0 then
--         return 0
--     elseif s <= 0 then
--         return INF_BAD
--     else
--         local r
--         if t <= 7230584 then
--             r = t * 297 / s
--         elseif s >= 1663497 then
--             r = t / floor(s / 297)
--         else
--             r = t
--         end
--         r = floor(r)
--         if r > 1290 then
--             return INF_BAD
--         else
--             return floor((r * r * r + 0x20000) / 0x40000) -- 0400000 / 01000000
--         end
--     end
-- end
--
-- left-overs
--
-- local function round_xn_over_d(x, n, d)
--     local positive -- was x >= 0
--     if x >= 0 then
--         positive = true
--     else
--         x = -x
--         positive = false
--     end
--     local t = floor(x % 0x8000) * n              -- 0100000
--     local f = floor(t / 0x8000)                  -- 0100000
--     local u = floor(x / 0x8000) * n + f          -- 0100000
--     local v = floor(u % d) * 0x8000 + f          -- 0100000
--     if floor(u / d) >= 0x8000 then               -- 0100000
--         report_parbuilders('arith_error')
--     else
--         u = 0x8000 * floor(u / d) + floor(v / d) -- 0100000
--     end
--     v = floor(v % d)
--     if 2*v >= d then
--         u = u + 1
--     end
--     if positive then
--         return u
--     else
--         return -u
--     end
-- end

function nodes.firstcharacter(n,untagged) -- tagged == subtype > 255
    if untagged then
        return first_glyph(n)
    else
        for g in traverse_id(glyph_code,n) do
            return g
        end
    end
end

function nodes.firstcharinbox(n)
    local l = texgetbox(n).list
    if l then
        for g in traverse_id(glyph_code,l) do
            return g.char
        end
    end
    return 0
end

if not node.end_of_math then
    function node.end_of_math(n)
        for n in traverse_id(math_code,n.next) do
            return n
        end
    end
end

nodes.endofmath = node.end_of_math

-- local function firstline(n)
--     while n do
--         local id = n.id
--         if id == hlist_code then
--             if n.subtype == line_code then
--                 return n
--             else
--                 return firstline(n.list)
--             end
--         elseif id == vlist_code then
--             return firstline(n.list)
--         end
--         n = n.next
--     end
-- end

-- nodes.firstline = firstline

-- this depends on fonts, so we have a funny dependency ... will be
-- sorted out .. we could make tonodes a plugin into this

local function tonodes(str,fnt,attr) -- (str,template_glyph) -- moved from blob-ini
    if not str or str == "" then
        return
    end
    local head, tail, space, fnt, template = nil, nil, nil, nil, nil
    if not fnt then
        fnt = current_font()
    elseif type(fnt) ~= "number" and fnt.id == "glyph" then
        fnt, template = nil, fnt
 -- else
     -- already a number
    end
    for s in utfvalues(str) do
        local n
        if s == 32 then
            if space then
                n = copy_node(space)
            elseif fonts then -- depedency
                local parameters = fonts.hashes.identifiers[fnt].parameters
                space = new_glue(parameters.space,parameters.space_stretch,parameters.space_shrink)
                n = space
            end
        elseif template then
            n = copy_node(template)
            n.char = s
        else
            n = new_glyph(fnt,s)
        end
        if attr then -- normally false when template
            n.attr = copy_node_list(attr)
        end
        if head then
            insert_node_after(head,tail,n)
        else
            head = n
        end
        tail = n
    end
    return head, tail
end

nodes.tonodes = tonodes

local function link(list,currentfont,currentattr,head,tail)
    for i=1,#list do
        local n = list[i]
        if n then
            local tn = isnode(n)
            if not tn then
                local tn = type(n)
                if tn == "number" then
                    if not currentfont then
                        currentfont = current_font()
                    end
                    local h, t = tonodes(tostring(n),currentfont,currentattr)
                    if not h then
                        -- skip
                    elseif not head then
                        head, tail = h, t
                    else
                        tail.next, h.prev, tail = h, t, t
                    end
                elseif tn == "string" then
                    if #tn > 0 then
                        if not currentfont then
                            currentfont = current_font()
                        end
                        local h, t = tonodes(n,currentfont,currentattr)
                        if not h then
                            -- skip
                        elseif not head then
                            head, tail = h, t
                        else
                            tail.next, h.prev, tail = h, t, t
                        end
                    end
                elseif tn == "table" then
                    if #tn > 0 then
                        if not currentfont then
                            currentfont = current_font()
                        end
                        head, tail = link(n,currentfont,currentattr,head,tail)
                    end
                end
            elseif not head then
                head = n
                if n.next then
                    tail = slide_nodes(n)
                else
                    tail = n
                end
            elseif n.id == attributelist_code then
                -- weird case
                report_error("weird node type in list at index %s:",i)
                for i=1,#list do
                    local l = list[i]
                    report_error("%3i: %s %S",i,l.id == attributelist_code and "!" or ">",l)
                end
                os.exit()
            else
                tail.next = n
                n.prev = tail
                if n.next then
                    tail = slide_nodes(n)
                else
                    tail = n
                end
            end
        else
            -- permitting nil is convenient
        end
    end
    return head, tail
end

nodes.link = link

local function locate(start,wantedid,wantedsubtype)
    for n in traverse_nodes(start) do
        local id = n.id
        if id == wantedid then
            if not wantedsubtype or n.subtype == wantedsubtype then
                return n
            end
        elseif id == hlist_code or id == vlist_code then
            local found = locate(n.list,wantedid,wantedsubtype)
            if found then
                return found
            end
        end
    end
end

nodes.locate =  locate

-- I have no use for this yet:
--
-- \skip0=10pt plus 2pt minus 2pt
-- \cldcontext{"\letterpercent p",tex.stretch_amount(tex.skip[0],1000)} -- 14.30887pt
--
-- local gluespec_code = nodes.nodecodes.gluespec
--
-- function tex.badness_to_ratio(badness)
--     return (badness/100)^(1/3)
-- end
--
-- function tex.stretch_amount(skip,badness)
--     if skip.id == gluespec_code then
--         return skip.width + (badness and (badness/100)^(1/3) or 1) * skip.stretch
--     else
--         return 0
--     end
-- end