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

local concat = table.concat

local nodes              = nodes

local tasks              = nodes.tasks
local nuts               = nodes.nuts
local nodepool           = nuts.pool

local tonode             = nuts.tonode
local tonut              = nuts.tonut

local getfield           = nuts.getfield
local setfield           = nuts.setfield
local getnext            = nuts.getnext
local getprev            = nuts.getprev
local getid              = nuts.getid
local getfont            = nuts.getfont
local getattr            = nuts.getattr
local getsubtype         = nuts.getsubtype
local getchar            = nuts.getchar

local copy_node          = nuts.copy
local free_node          = nuts.free
local remove_node        = nuts.remove
local traverse_id        = nuts.traverse_id
local traverse_nodes     = nuts.traverse

local nodecodes          = nodes.nodecodes
local disccodes          = nodes.disccodes

local disc_code          = nodecodes.disc
local glyph_code         = nodecodes.glyph
local discretionary_code = disccodes.discretionary

local a_visualize        = attributes.private("visualizediscretionary")
local setattribute       = tex.setattribute

local getlanguagedata    = languages.getdata

local expanders = {
    [disccodes.discretionary] = function(d,template)
        -- \discretionary
        return template
    end,
    [disccodes.explicit] = function(d,template)
        -- \-
        local pre = getfield(d,"pre")
        if pre and getid(pre) == glyph_code and getchar(pre) <= 0 then
            setfield(d,"pre",nil)
        end
        local post = getfield(d,"post")
        if post and getid(post) == glyph_code and getchar(post) <= 0 then
            setfield(d,"post",nil)
        end
--         setfield(d,"subtype",discretionary_code) -- to be checked
        return template
    end,
    [disccodes.automatic] = function(d,template)
        -- following a - : the pre and post chars are already appended and set
        -- so we have pre=preex and post=postex .. however, the previous
        -- hyphen is already injected ... downside: the font handler sees this
        -- so this is another argument for doing a hyphenation pass in context
        if getfield(d,"pre") then
            -- we have a preex characters and want that one to replace the
            -- character in front which is the trigger
            if not template then
                -- can there be font kerns already?
                template = getprev(d)
                if template and getid(template) ~= glyph_code then
                    template = getnext(d)
                    if template and getid(template) ~= glyph_code then
                        template = nil
                    end
                end
            end
            if template then
                local pseudohead = getprev(template)
                if pseudohead then
                    while template ~= d do
                        pseudohead, template, removed = remove_node(pseudohead,template)
                        setfield(d,"replace",removed)
                        -- break ?
                    end
                else
                    -- can't happen
                end
                setfield(d,"subtype",discretionary_code)
            else
             -- print("lone regular discretionary ignored")
            end
        end
        return template
    end,
    [disccodes.regular] = function(d,template)
        -- simple
        if not template then
            -- can there be font kerns already?
            template = getprev(d)
            if template and getid(template) ~= glyph_code then
                template = getnext(d)
                if template and getid(template) ~= glyph_code then
                    template = nil
                end
            end
        end
        if template then
            local language = template and getfield(template,"lang")
            local data     = getlanguagedata(language)
            local prechar  = data.prehyphenchar
            local postchar = data.posthyphenchar
            if prechar and prechar > 0 then
                local c = copy_node(template)
                setfield(c,"char",prechar)
                setfield(d,"pre",c)
            end
            if postchar and postchar > 0 then
                local c = copy_node(template)
                setfield(c,"char",postchar)
                setfield(d,"post",c)
            end
            setfield(d,"subtype",discretionary_code)
        else
         -- print("lone regular discretionary ignored")
        end
        return template
    end,
    [disccodes.first] = function()
        -- forget about them
    end,
    [disccodes.second] = function()
        -- forget about them
    end,
}

languages.expanders = expanders

function languages.expand(d,template,subtype)
    if not subtype then
        subtype = getsubtype(d)
    end
    if subtype ~= discretionary_code then
        return expanders[subtype](d,template)
    end
end

local setlistcolor = nodes.tracers.colors.setlist

function languages.visualizediscretionaries(head)
    for d in traverse_id(disc_code,tonut(head)) do
        if getattr(d,a_visualize) then
            local pre     = getfield(d,"pre")
            local post    = getfield(d,"post")
            local replace = getfield(d,"replace")
            if pre then
                setlistcolor(pre,"darkred")
            end
            if post then
                setlistcolor(post,"darkgreen")
            end
            if replace then
                setlistcolor(replace,"darkblue")
            end
        end
    end
end

local enabled = false

function commands.showdiscretionaries(v)
    if v == false then
        setattribute(a_visualize,unsetvalue)
    else -- also nil
        if not enabled then
            nodes.tasks.enableaction("processors","languages.visualizediscretionaries")
            enabled = true
        end
        setattribute(a_visualize,1)
    end
end

local toutf = nodes.listtoutf

function languages.serializediscretionary(d) -- will move to tracer
    return string.formatters["{%s}{%s}{%s}"](
        toutf(getfield(d,"pre")) or "",
        toutf(getfield(d,"post")) or "",
        toutf(getfield(d,"replace")) or ""
    )
end