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

-- todo: recycle slots better
-- todo: hoffset
-- todo: auto-increase line height
-- todo: only hpack when start <> stop

-- A typical bit of afternoon hackery ... with some breaks for watching
-- Ghost-Note on youtube (Robert Searight and Nate Werth) ... which expands
-- my to-be-had cd/dvd list again.

local lpegmatch         = lpeg.match
local utfcharacters     = utf.characters
local setmetatableindex = table.setmetatableindex

local variables       = interfaces.variables
local implement       = interfaces.implement

local texsetattribute = tex.setattribute

local v_flushleft     = variables.flushleft
local v_middle        = variables.middle
local v_flushright    = variables.flushright
local v_yes           = variables.yes
local v_no            = variables.no
local v_auto          = variables.auto

local nuts            = nodes.nuts

local getid           = nuts.getid
local getsubtype      = nuts.getsubtype
local getattr         = nuts.getattr
local setattr         = nuts.setattr
local getnext         = nuts.getnext
local setnext         = nuts.setnext
local getprev         = nuts.getprev
local setprev         = nuts.setprev
local setlink         = nuts.setlink
local getlist         = nuts.getlist
local setlist         = nuts.setlist
local setshift        = nuts.setshift
local getwidth        = nuts.getwidth
local setwidth        = nuts.setwidth

local hpack           = nuts.hpack
local takebox         = nuts.takebox

local nextlist        = nuts.traversers.list

local nodecodes       = nodes.nodecodes
local glyph_code      = nodecodes.glyph
local disc_code       = nodecodes.disc
local kern_code       = nodecodes.kern
local glue_code       = nodecodes.glue
local penalty_code    = nodecodes.penalty
local hlist_code      = nodecodes.hlist
local vlist_code      = nodecodes.vlist
local par_code        = nodecodes.par
local dir_code        = nodecodes.dir

local kerncodes       = nodes.kerncodes
local fontkern_code   = kerncodes.font

local nodepool        = nuts.pool
local new_kern        = nodepool.kern

local setprop         = nuts.setprop
local getprop         = nuts.getprop

local findattribute   = nuts.findattribute

local enableaction    = nodes.tasks.enableaction

local nofrubies       = 0
local rubylist        = { }

local a_ruby          = attributes.private("ruby")

local rubies          = { }
typesetters.rubies    = rubies

local trace_rubies    = false  trackers.register("typesetters.rubies",function(v) trace_rubies = v end)
local report_rubies   = logs.reporter("rubies")

-- todo: use the more modern lmtx storage model

local registervalue   = attributes.registervalue
local getvalue        = attributes.getvalue
local texsetattribute = tex.setattribute

do

    local shared   = nil
    local splitter = lpeg.tsplitat("|")

    local function enable()
        enableaction("processors","typesetters.rubies.check")
        enableaction("shipouts",  "typesetters.rubies.attach")
        enable = false
    end

    local ctx_setruby = context.core.setruby

    local function ruby(settings)
        local base    = settings.base
        local comment = settings.comment
        shared = settings
        local c = lpegmatch(splitter,comment)
        if #c == 1 then
            ctx_setruby(base,comment)
            if trace_rubies then
                report_rubies("- %s -> %s",base,comment)
            end
        else
            local i = 0
            for b in utfcharacters(base) do
                i = i + 1
                local r = c[i]
                if r then
                    ctx_setruby(b,r)
                    if trace_rubies then
                        report_rubies("%i: %s -> %s",i,b,r)
                    end
                else
                    ctx_setruby(b,"")
                    if trace_rubies then
                        report_rubies("%i: %s",i,b)
                    end
                end
            end
        end
        if enable then
            enable()
        end
    end

    local function startruby(settings)
        shared = settings
        if enable then
            enable()
        end
    end

    implement {
        name      = "ruby",
        actions   = ruby,
        arguments = {
            {
                { "align" },
                { "stretch" },
                { "hoffset", "dimension" },
                { "voffset", "dimension" },
                { "comment" },
                { "base" },
            }
        },
    }

    implement {
        name      = "startruby",
        actions   = startruby,
        arguments = {
            {
                { "align" },
                { "stretch" },
                { "hoffset", "dimension" },
                { "voffset", "dimension" },
            }
        },
    }

    local function setruby(n,m)
        nofrubies = nofrubies + 1
        local r = takebox(n)
        local t = {
            text      = r,
            width     = getwidth(r),
            basewidth = 0,
            start     = false,
            stop      = false,
        }
     -- rubylist[nofrubies] = setmetatableindex(t,shared)
     -- texsetattribute(a_ruby,nofrubies)
        texsetattribute(a_ruby,registervalue(a_ruby,setmetatableindex(t,shared)))
    end

    implement {
        name      = "setruby",
        actions   = setruby,
        arguments = "integer",
    }

end

-- function rubies.check(head)
--     local current = head
--     local start   = nil
--     local stop    = nil
--     local found   = nil
--
--     local function flush(where)
--         local r = rubylist[found]
--         if r then
--             local prev = getprev(start)
--             local next = getnext(stop)
--             setprev(start)
--             setnext(stop)
--             local h = hpack(start)
--             if start == head then
--                 head = h
--             else
--                 setlink(prev,h)
--             end
--             setlink(h,next)
--             local bwidth = getwidth(h)
--             local rwidth = r.width
--             r.basewidth  = bwidth
--             r.start      = start
--             r.stop       = stop
--             setprop(h,"ruby",found)
--             if rwidth > bwidth then
--                 -- ruby is wider
--                 setwidth(h,rwidth)
--             end
--         end
--     end
--
--     while current do
--         local nx = getnext(current)
--         local id = getid(current)
--         if id == glyph_code then
--             local a  = getattr(current,a_ruby)
--             if not a then
--                 if found then
--                     flush("flush 1")
--                     found = nil
--                 end
--             elseif a == found then
--                 stop = current
--             else
--                 if found then
--                     flush("flush 2")
--                 end
--                 found = a
--                 start = current
--                 stop  = current
--             end
--             -- go on
--         elseif id == kern_code and getsubtype(current,fontkern_code) then
--             -- go on
--         elseif found and id == disc_code then
--             -- go on (todo: look into disc)
--         elseif found then
--             flush("flush 3")
--             found = nil
--         end
--         current = nx
--     end
--
--     if found then
--         flush("flush 4")
--     end
--     return head, true -- no need for true
-- end

function rubies.check(head)
    local _, current = findattribute(head,a_ruby)
    if current then

        local start   = nil
        local stop    = nil
        local found   = nil

        local function flush(where)
--            local r = rubylist[found]
local r = getvalue(a_ruby,found)
            if r then
                -- can be an option
                while start ~= stop and getid(start) == glue_code do
                    start = getnext(start)
                end
                while stop ~= start and getid(stop) == glue_code do
                    stop = getprev(stop)
                end
                --
                local prev = getprev(start)
                local next = getnext(stop)
                setprev(start)
                setnext(stop)
                local h = hpack(start)
                if start == head then
                    head = h
                else
                    setlink(prev,h)
                end
                setlink(h,next)
                local bwidth = getwidth(h)
                local rwidth = r.width
                r.basewidth  = bwidth
                r.start      = start
                r.stop       = stop
                setprop(h,"ruby",found)
                if rwidth > bwidth then
                    -- ruby is wider
                    setwidth(h,rwidth)
                end
            end
        end

--         while current do
--             local nx = getnext(current)
--             local a  = getattr(current,a_ruby)
--             if not a then
--                 if found then
--                     flush("flush 1")
--                     found = nil
--                 end
--             elseif a == found then
--                 stop = current
--             else
--                 if found then
--                     flush("flush 2")
--                 end
--                 found = a
--                 start = current
--                 stop  = current
--             end
--             current = nx
--         end

        -- todo: we can avoid a lookup

        while current do
            local nx = getnext(current)
            local a  = getattr(current,a_ruby)
            if not a then
                if found then
                    flush("flush 1")
                    found = nil
                end
_, current = findattribute(nx,a_ruby)
            elseif a == found then
                stop = current
current = nx
            else
                if found then
                    flush("flush 2")
                end
                found = a
                start = current
                stop  = current
current = nx
            end
        end

    end

    if found then
        flush("flush 4")
    end
    return head, true -- no need for true
end


local attach

local function whatever(current,list)
    local a = getprop(current,"ruby")
    if a then
--         local ruby    = rubylist[a]
local ruby = getvalue(a_ruby,a)
        local align   = ruby.align   or v_middle
        local stretch = ruby.stretch or v_no
        local hoffset = ruby.hoffset or 0
        local voffset = ruby.voffset or 0
        local start   = ruby.start
        local stop    = ruby.stop
        local text    = ruby.text
        local rwidth  = ruby.width
        local bwidth  = ruby.basewidth
        local delta   = rwidth - bwidth
        setwidth(text,0)
        if voffset ~= 0 then
            setshift(text,voffset)
        end
        -- center them
        if delta > 0 then
            -- ruby is wider
            if stretch == v_yes then
                setlink(text,start)
                while start and start ~= stop do
                    local s = nodepool.stretch()
                    local n = getnext(start)
                    setlink(start,s,n)
                    start = n
                end
                text = hpack(text,rwidth,"exactly")
            else
                local left  = new_kern(delta/2)
                local right = new_kern(delta/2)
                setlink(text,left,start)
                setlink(stop,right)
            end
            setlist(current,text)
        elseif delta < 0 then
            -- ruby is narrower
            if align == v_auto then
                local l = true
                local c = getprev(current)
                while c do
                    local id = getid(c)
                    if id == glue_code or id == penalty_code or id == kern_code then
                        -- go on
                    elseif id == hlist_code and getwidth(c) == 0 then
                        -- go on
                    elseif id == whatsit_code or id == par_code or id == dir_code then
                        -- go on
                    else
                        l = false
                        break
                    end
                    c = getprev(c)
                end
                local r = true
                local c = getnext(current)
                while c do
                    local id = getid(c)
                    if id == glue_code or id == penalty_code or id == kern_code then
                        -- go on
                    elseif id == hlist_code and getwidth(c) == 0 then
                        -- go on
                    else
                        r = false
                        break
                    end
                    c = getnext(c)
                end
                if l and not r then
                    align = v_flushleft
                elseif r and not l then
                    align = v_flushright
                else
                    align = v_middle
                end
            end
            if align == v_flushleft then
                setlink(text,start)
                setlist(current,text)
            elseif align == v_flushright then
                local left  = new_kern(-delta)
                local right = new_kern(delta)
                setlink(left,text,right,start)
                setlist(current,left)
            else
                local left  = new_kern(-delta/2)
                local right = new_kern(delta/2)
                setlink(left,text,right,start)
                setlist(current,left)
            end
        else
            setlink(text,start)
            setlist(current,text)
        end
        setprop(current,"ruby",false)
--         rubylist[a] = nil
    elseif list then
        attach(list)
    end
end

attach = function(head)
    for current, id, subtype, list in nextlist, head do
        if id == hlist_code or id == vlist_code then
            whatever(current,list)
        end
    end
    return head
end

rubies.attach = attach

-- for now there is no need to be compact

-- local data          = { }
-- rubies.data         = data
--
-- function rubies.define(settings)
--     data[#data+1] = settings
--     return #data
-- end
--
-- implement {
--     name      = "defineruby",
--     actions   = { rubies.define, context },
--     arguments = {
--         {
--             { "align" },
--             { "stretch" },
--         }
--     }
-- }