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

-- todo: have a local list with local tags that then get appended
-- todo: use tex.getmathcodes (no table)

-- use lpeg matchers

local find, match = string.find, string.match
local insert, remove, concat = table.insert, table.remove, table.concat

local attributes        = attributes
local nodes             = nodes

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

local getnext           = nuts.getnext
local getid             = nuts.getid
local getchar           = nuts.getchar
local getfont           = nuts.getfont
local getlist           = nuts.getlist
local getfield          = nuts.getfield
local getdisc           = nuts.getdisc
local getsubtype        = nuts.getsubtype
local getattr           = nuts.getattr
local getattrlist       = nuts.getattrlist
local setattr           = nuts.setattr
local getcomponents     = nuts.getcomponents -- not really needed
local getwidth          = nuts.getwidth

local getnucleus        = nuts.getnucleus
local getsub            = nuts.getsub
local getsup            = nuts.getsup

local set_attributes    = nuts.setattributes

local nextnode          = nuts.traversers.node

local nodecodes         = nodes.nodecodes

local noad_code         = nodecodes.noad           -- attr nucleus sub sup
local accent_code       = nodecodes.accent         -- attr nucleus sub sup accent
local radical_code      = nodecodes.radical        -- attr nucleus sub sup left degree
local fraction_code     = nodecodes.fraction       -- attr nucleus sub sup left right
local subbox_code       = nodecodes.subbox         -- attr list
local submlist_code     = nodecodes.submlist       -- attr list
local mathchar_code     = nodecodes.mathchar       -- attr fam char
local mathtextchar_code = nodecodes.mathtextchar   -- attr fam char
local delim_code        = nodecodes.delim          -- attr small_fam small_char large_fam large_char
local style_code        = nodecodes.style          -- attr style
local choice_code       = nodecodes.choice         -- attr display text script scriptscript
local fence_code        = nodecodes.fence          -- attr subtype

local accentcodes       = nodes.accentcodes
local fencecodes        = nodes.fencecodes

local fixedtopaccent_code    = accentcodes.fixedtop
local fixedbottomaccent_code = accentcodes.fixedbottom
local fixedbothaccent_code   = accentcodes.fixedboth

local leftfence_code    = fencecodes.left
local middlefence_code  = fencecodes.middle
local rightfence_code   = fencecodes.right

local kerncodes         = nodes.kerncodes

local fontkern_code     = kerncodes.fontkern
local italickern_code   = kerncodes.italickern

local hlist_code        = nodecodes.hlist
local vlist_code        = nodecodes.vlist
local glyph_code        = nodecodes.glyph
local disc_code         = nodecodes.disc
local glue_code         = nodecodes.glue
local kern_code         = nodecodes.kern
local math_code         = nodecodes.math

local processnoads      = noads.process

local a_tagged          = attributes.private('tagged')
local a_mathcategory    = attributes.private('mathcategory')
local a_mathmode        = attributes.private('mathmode')

local tags              = structures.tags

local start_tagged      = tags.start
local restart_tagged    = tags.restart
local stop_tagged       = tags.stop
local taglist           = tags.taglist

local chardata          = characters.data

local getmathcodes      = tex.getmathcodes
local mathcodes         = mathematics.codes
local ordinary_mathcode = mathcodes.ordinary
local variable_mathcode = mathcodes.variable

local fromunicode16     = fonts.mappings.fromunicode16
local fontcharacters    = fonts.hashes.characters

local report_tags       = logs.reporter("structure","tags")

local process

local function processsubsup(start)
    -- At some point we might need to add an attribute signaling the
    -- super- and subscripts because TeX and MathML use a different
    -- order. The mrows are needed to keep mn's separated.
    local nucleus = getnucleus(start)
    local sup     = getsup(start)
    local sub     = getsub(start)
    if sub then
        if sup then
            setattr(start,a_tagged,start_tagged("msubsup"))
         -- start_tagged("mrow")
            process(nucleus)
         -- stop_tagged()
            start_tagged("mrow", { subscript = true })
            process(sub)
            stop_tagged()
            start_tagged("mrow", { superscript = true })
            process(sup)
            stop_tagged()
            stop_tagged()
        else
            setattr(start,a_tagged,start_tagged("msub"))
         -- start_tagged("mrow")
            process(nucleus)
         -- stop_tagged()
            start_tagged("mrow")
            process(sub)
            stop_tagged()
            stop_tagged()
        end
    elseif sup then
        setattr(start,a_tagged,start_tagged("msup"))
     -- start_tagged("mrow")
        process(nucleus)
     -- stop_tagged()
        start_tagged("mrow")
        process(sup)
        stop_tagged()
        stop_tagged()
    else
        process(nucleus)
    end
end

-- todo: check function here and keep attribute the same

-- todo: variants -> original

local actionstack = { }
local fencesstack = { }

-- glyph nodes and such can happen in under and over stuff

-- local function getunicode(n) -- instead of getchar
--     local char = getchar(n)
--  -- local font = getfontoffamily(getfield(n,"fam"))
--     local font = getfont(n)
--     local data = fontcharacters[font][char]
--     return data.unicode or char
-- end

local function getunicode(n) -- instead of getchar
 -- local char, font = isglyph(n) -- no, we have a mathchar
    local char, font = getchar(n), getfont(n)
    local data = fontcharacters[font][char]
    return data.unicode or char -- can be a table but unlikely for math characters
end

-------------------

local content = { }
local found   = false

content[mathchar_code] = function() found = true end

local function hascontent(head)
    found = false
    processnoads(head,content,"content")
    return found
end

--------------------

-- todo: use properties

-- local function showtag(n,id,old)
--     local attr = getattr(n,a_tagged)
--     local curr = tags.current()
--     report_tags("%s, node %s, attr %s:%s (%s), top %s (%s)",
--         old and "before" or "after ",
--         nodecodes[id],
--         getattrlist(n),
--         attr or "?",attr and taglist[attr].tagname or "?",
--         curr or "?",curr and taglist[curr].tagname or "?"
--     )
-- end

process = function(start) -- we cannot use the processor as we have no finalizers (yet)
    local mtexttag = nil
    while start do
        local id = getid(start)
-- showtag(start,id,true)
        if id == glyph_code or id == disc_code then
            if not mtexttag then
                mtexttag = start_tagged("mtext")
            end
            setattr(start,a_tagged,mtexttag)
        elseif mtexttag and id == kern_code and (getsubtype(start) == fontkern_code or getsubtype(start) == italickern_code) then -- italickern
            setattr(start,a_tagged,mtexttag)
        else
            if mtexttag then
                stop_tagged()
                mtexttag = nil
            end
            if id == mathchar_code then
                local char = getchar(start)
                local code = getmathcodes(char)
                local tag
                if code == ordinary_mathcode or code == variable_mathcode then
                    local ch = chardata[char]
                    local mc = ch and ch.mathclass
                    if mc == "number" then
                        tag = "mn"
                    elseif mc == "variable" or not mc then -- variable is default
                        tag = "mi"
                    else
                        tag = "mo"
                    end
                else
                    tag = "mo"
                end
                local a = getattr(start,a_mathcategory)
                if a then
                    setattr(start,a_tagged,start_tagged(tag,{ mathcategory = a }))
                else
                    setattr(start,a_tagged,start_tagged(tag)) -- todo: a_mathcategory
                end
                stop_tagged()
             -- showtag(start,id,false)
                break -- okay?
            elseif id == mathtextchar_code then -- or id == glyph_code
                -- check for code
                local a = getattr(start,a_mathcategory)
                if a then
                    setattr(start,a_tagged,start_tagged("ms",{ mathcategory = a })) -- mtext
                else
                    setattr(start,a_tagged,start_tagged("ms")) -- mtext
                end
                stop_tagged()
             -- showtag(start,id,false)
                break
            elseif id == delim_code then
                -- check for code
                setattr(start,a_tagged,start_tagged("mo"))
                stop_tagged()
             -- showtag(start,id,false)
                break
            elseif id == style_code then
                -- has a next
            elseif id == noad_code then
             -- setattr(start,a_tagged,tags.current())
                processsubsup(start)
            elseif id == subbox_code or id == hlist_code or id == vlist_code then
                -- keep an eye on subbox_code and see what ends up in there
                local attr = getattr(start,a_tagged)
                if not attr then
                    -- just skip
                else
                    local specification = taglist[attr]
                    if specification then
                        local tag = specification.tagname
                        if tag == "formulacaption" then
                            -- skip
                        elseif tag == "mstacker" then
                            local list = getlist(start)
                            if list then
                                process(list)
                            end
                        else
                            if tag ~= "mstackertop" and tag ~= "mstackermid" and tag ~= "mstackerbot" then
                                tag = "mtext"
                            end
                            local text = start_tagged(tag)
                            setattr(start,a_tagged,text)
                            local list = getlist(start)
                            if not list then
                                -- empty list
                            elseif not attr then
                                -- box comes from strange place
                                set_attributes(list,a_tagged,text) -- only the first node ?
                            else
                                -- Beware, the first node in list is the actual list so we definitely
                                -- need to nest. This approach is a hack, maybe I'll make a proper
                                -- nesting feature to deal with this at another level. Here we just
                                -- fake structure by enforcing the inner one.
                                --
                                -- todo: have a local list with local tags that then get appended
                                --
                                local tagdata = specification.taglist
                                local common = #tagdata + 1
                                local function runner(list,depth) -- quite inefficient
                                    local cache = { } -- we can have nested unboxed mess so best local to runner
                                    local keep = nil
                                 -- local keep = { } -- win case we might need to move keep outside
                                    for n, id, subtype in nextnode, list do
                                        local mth = id == math_code and subtype
                                        if mth == 0 then -- hm left_code
                                         -- insert(keep,text)
                                            keep = text
                                            text = start_tagged("mrow")
                                            common = common + 1
                                        end
                                        local aa = getattr(n,a_tagged)
                                        if aa then
                                            local ac = cache[aa]
                                            if not ac then
                                                local tagdata = taglist[aa].taglist
                                                local extra = #tagdata
                                                if common <= extra then
                                                    for i=common,extra do
                                                        ac = restart_tagged(tagdata[i]) -- can be made faster
                                                    end
                                                    for i=common,extra do
                                                        stop_tagged() -- can be made faster
                                                    end
                                                else
                                                    ac = text
                                                end
                                                cache[aa] = ac
                                            end
                                            setattr(n,a_tagged,ac)
                                        else
                                            setattr(n,a_tagged,text)
                                        end
                                        if id == hlist_code or id == vlist_code then
                                            runner(getlist(n),depth+1)
                                        elseif id == glyph_code then
                                            -- this should not be needed
                                            local components = getcomponents(n) -- unlikely set
                                            if components then
                                                runner(getcomponent,depth+1)
                                            end
                                        elseif id == disc_code then
                                            -- this should not be needed
                                            local pre, post, replace = getdisc(n)
                                            if pre then
                                                runner(pre,depth+1)
                                            end
                                            if post then
                                                runner(post,depth+1)
                                            end
                                            if replace then
                                                runner(replace,depth+1)
                                            end
                                        end
                                        if mth == 1 then
                                            stop_tagged()
                                         -- text = remove(keep)
                                            text = keep
                                            common = common - 1
                                        end
                                    end
                                end
                                runner(list,0)
                            end
                            stop_tagged()
                        end
                    end
                end
            elseif id == submlist_code then -- normally a hbox
                local list = getlist(start)
                if list then
                    local attr = getattr(start,a_tagged)
                    local last = attr and taglist[attr]
                    if last then
                        local tag    = last.tagname
                        local detail = last.detail
                        if tag == "maction" then
                            if detail == "" then
                                setattr(start,a_tagged,start_tagged("mrow"))
                                process(list)
                                stop_tagged()
                            elseif actionstack[#actionstack] == action then
                                setattr(start,a_tagged,start_tagged("mrow"))
                                process(list)
                                stop_tagged()
                            else
                                insert(actionstack,action)
                                setattr(start,a_tagged,start_tagged("mrow",{ detail = action }))
                                process(list)
                                stop_tagged()
                                remove(actionstack)
                            end
                        elseif tag == "mstacker" then -- or tag == "mstackertop" or tag == "mstackermid" or tag == "mstackerbot" then
                            -- looks like it gets processed twice
                            -- do we still end up here ?
                            setattr(start,a_tagged,restart_tagged(attr)) -- so we just reuse the attribute
                            process(list)
                            stop_tagged()
                        else
                            setattr(start,a_tagged,start_tagged("mrow"))
                            process(list)
                            stop_tagged()
                        end
                    else -- never happens, we're always document
                        setattr(start,a_tagged,start_tagged("mrow"))
                        process(list)
                        stop_tagged()
                    end
                end
            elseif id == fraction_code then
                local num   = getfield(start,"num")
                local denom = getfield(start,"denom")
                local left  = getfield(start,"left")
                local right = getfield(start,"right")
                if left then
                   setattr(left,a_tagged,start_tagged("mo"))
                   process(left)
                   stop_tagged()
                end
                setattr(start,a_tagged,start_tagged("mfrac"))
                process(num)
                process(denom)
                stop_tagged()
                if right then
                    setattr(right,a_tagged,start_tagged("mo"))
                    process(right)
                    stop_tagged()
                end
            elseif id == choice_code then
                local display      = getfield(start,"display")
                local text         = getfield(start,"text")
                local script       = getfield(start,"script")
                local scriptscript = getfield(start,"scriptscript")
                if display then
                    process(display)
                end
                if text then
                    process(text)
                end
                if script then
                    process(script)
                end
                if scriptscript then
                    process(scriptscript)
                end
            elseif id == fence_code then
                local subtype = getsubtype(start)
                local delim   = getfield(start,"delim")
                if subtype == leftfence_code then
                    -- left
                    local properties = { }
                    insert(fencesstack,properties)
                    setattr(start,a_tagged,start_tagged("mfenced",properties)) -- needs checking
                    if delim then
                        start_tagged("ignore")
                        local chr = getchar(delim)
                        if chr ~= 0 then
                            properties.left = chr
                        end
                        process(delim)
                        stop_tagged()
                    end
                    start_tagged("mrow") -- begin of subsequence
                elseif subtype == middlefence_code then
                    -- middle
                    if delim then
                        start_tagged("ignore")
                        local top = fencesstack[#fencesstack]
                        local chr = getchar(delim)
                        if chr ~= 0 then
                            local mid = top.middle
                            if mid then
                                mid[#mid+1] = chr
                            else
                                top.middle = { chr }
                            end
                        end
                        process(delim)
                        stop_tagged()
                    end
                    stop_tagged()        -- end of subsequence
                    start_tagged("mrow") -- begin of subsequence
                elseif subtype == rightfence_code then
                    local properties = remove(fencesstack)
                    if not properties then
                        report_tags("missing right fence")
                        properties = { }
                    end
                    if delim then
                        start_tagged("ignore")
                        local chr = getchar(delim)
                        if chr ~= 0 then
                            properties.right = chr
                        end
                        process(delim)
                        stop_tagged()
                    end
                    stop_tagged() -- end of subsequence
                    stop_tagged()
                else
                    -- can't happen
                end
            elseif id == radical_code then
                local left   = getfield(start,"left")
                local degree = getfield(start,"degree")
                if left then
                    start_tagged("ignore")
                    process(left) -- root symbol, ignored
                    stop_tagged()
                end
                if degree and hascontent(degree) then
                    setattr(start,a_tagged,start_tagged("mroot"))
                    processsubsup(start)
                    process(degree)
                    stop_tagged()
                else
                    setattr(start,a_tagged,start_tagged("msqrt"))
                    processsubsup(start)
                    stop_tagged()
                end
            elseif id == accent_code then
                local subtype    = getsubtype(start)
                local accent     = getfield(start,"accent")
                local bot_accent = getfield(start,"bot_accent")
                if bot_accent then
                    if accent then
                        setattr(start,a_tagged,start_tagged("munderover", {
                            accent      = true,
                            top         = getunicode(accent),
                            bottom      = getunicode(bot_accent),
                            topfixed    = subtype == fixedtopaccent_code or subtype == fixedbothaccent_code,
                            bottomfixed = subtype == fixedbottomaccent_code or subtype == fixedbothaccent_code,
                        }))
                        processsubsup(start)
                        process(bot_accent)
                        process(accent)
                        stop_tagged()
                    else
                        setattr(start,a_tagged,start_tagged("munder", {
                            accent      = true,
                            bottom      = getunicode(bot_accent),
                            bottomfixed = subtype == fixedbottomaccent_code or subtype == fixedbothaccent_code,
                        }))
                        processsubsup(start)
                        process(bot_accent)
                        stop_tagged()
                    end
                elseif accent then
                    setattr(start,a_tagged,start_tagged("mover", {
                        accent   = true,
                        top      = getunicode(accent),
                        topfixed = subtype == fixedtopaccent_code or subtype == fixedbothaccent_code,
                    }))
                    processsubsup(start)
                    process(accent)
                    stop_tagged()
                else
                    processsubsup(start)
                end
            elseif id == glue_code then
             -- setattr(start,a_tagged,start_tagged("mspace",{ width = getwidth(start) }))
                setattr(start,a_tagged,start_tagged("mspace"))
                stop_tagged()
            else
                setattr(start,a_tagged,start_tagged("merror", { detail = nodecodes[i] }))
                stop_tagged()
            end
        end
-- showtag(start,id,false)
        start = getnext(start)
    end
    if mtexttag then
        stop_tagged()
    end
end

function noads.handlers.tags(head,style,penalties)
    start_tagged("math", { mode = (getattr(head,a_mathmode) == 1) and "display" or "inline" })
    setattr(head,a_tagged,start_tagged("mrow"))
-- showtag(head,getid(head),true)
    process(head)
-- showtag(head,getid(head),false)
    stop_tagged()
    stop_tagged()
end