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

local format = string.format
local next = next
local texsprint, texwrite, texcount = tex.sprint, tex.write, tex.count

local ctxcatcodes = tex.ctxcatcodes

local trace_notes = false  trackers.register("structure.notes", function(v) trace_notes = v end)

structure              = structure          or { }
structure.helpers      = structure.helpers  or { }
structure.lists        = structure.lists    or { }
structure.sections     = structure.sections or { }
structure.counters     = structure.counters or { }
structure.notes        = structure.notes    or { }

structure.notes.states    = structure.notes.states    or { }
structure.lists.enhancers = structure.lists.enhancers or { }

storage.register("structure/notes/states", structure.notes.states, "structure.notes.states")

local helpers  = structure.helpers
local lists    = structure.lists
local sections = structure.sections
local counters = structure.counters
local notes    = structure.notes

local notestates = structure.notes.states
local notedata   = { }

-- state: store, insert, postpone

function notes.store(tag,n)
    local nd = notedata[tag]
    if not nd then
        nd = { }
        notedata[tag] = nd
    end
    local nnd = #nd+1
    nd[nnd] = n
    local state = notestates[tag]
    if state.kind ~= "insert" then
        if trace_notes then
            logs.report("notes","storing %s with state %s as %s",tag,state.kind,nnd)
        end
        state.start = state.start or nnd
    end
    texwrite(#nd)
end

local function get(tag,n)
    local nd = notedata[tag]
    if nd then
        n = n or #nd
        nd = nd[n]
        if nd then
            if trace_notes then
                logs.report("notes","getting %s of %s",n,tag)
            end
            return structure.lists.collected[nd]
        end
    end
end

local function getn(tag)
    local nd = notedata[tag]
    return (nd and #nd) or 0
end

nodes.get = get
nodes.getn = getn

-- we could make a special enhancer

function notes.listindex(tag,n)
    return notedata[tag][n]
end

function notes.define(tag,kind,number)
    local state = notes.setstate(tag,kind)
    state.number = number
end

function notes.save(tag,newkind)
    local state = notestates[tag]
    if state and not state.saved then
        if trace_notes then
            logs.report("notes","saving state of %s: %s -> %s",tag,state.kind,newkind or state.kind)
        end
        state.saved = notedata[tag]
        state.savedkind = state.kind
        state.kind = newkind or state.kind
        notedata[tag] = { }
    end
end

function notes.restore(tag,forcedstate)
    local state = notestates[tag]
    if state and state.saved then
        if trace_notes then
            logs.report("notes","restoring state of %s: %s -> %s",tag,state.kind,state.savedkind)
        end
        state.saved = nil
        state.kind = forcedstate or state.savedkind
        notedata[tag] = state.saved
    end
end

function notes.setstate(tag,newkind)
    local state = notestates[tag]
    if trace_notes then
        logs.report("notes","setting state of %s from %s to %s",tag,(state and state.kind) or "unset",newkind)
    end
    if not state then
        state = {
            kind = newkind
        }
        notestates[tag] = state
    elseif newkind == "insert" then
        if not state.start then
            state.kind = newkind
        end
    else
        state.kind = newkind
    end
    --  state.start can already be set and will be set when an entry is added or flushed
    return state
end

function notes.getstate(tag)
    local state = notestates[tag]
    texsprint(ctxcatcodes,(state and state.kind ) or "unknown")
end

function notes.doifcontent(tag)
    local ok = notestates[tag]
    if ok then
        if ok.kind == "insert" then
            ok = tex.box[ok.number]
            if ok then
                ok = tbs.list
                ok = lst and lst.next
            end
        else
            ok = ok.start
        end
    end
    commands.doif(ok)
end

local function internal(tag,n)
    local nd = get(tag,n)
    if nd then
        local r = nd.references
        if r then
            local i = r.internal
--~             return i and lists.internals[i]
            return i and jobreferences.internals[i]
        end
    end
    return nil
end

local function ordered(kind,name,n)
    local o = lists.ordered[kind]
    o = o and o[name]
    return o and o[n]
end

notes.internal = internal
notes.ordered  = ordered

function notes.doifonsamepageasprevious(tag)
    local same = false
    local n = getn(tag,n)
    local current, previous = get(tag,n), get(tag,n-1)
    if current and previous then
        local cr, pr = current.references, previous.references
        same = cr and pr and cr.realpage == pr.realpage
    end
    commands.doifelse(same)
end

function notes.checkpagechange(tag) -- called before increment !
    local nd = notedata[tag] -- can be unset at first entry
    if nd then
        local current = ordered("note",tag,#nd)
        local nextone = ordered("note",tag,#nd+1)
        if nextone then
            -- we can use data from the previous pass
            if nextone.pagenumber.number > current.pagenumber.number then
                counters.reset(tag)
            end
        elseif current then
            -- we need to locate the next one, best guess
            if texcount.realpageno > current.pagenumber.number then
                counters.reset(tag)
            end
        end
    end
end

function notes.deltapage(tag,n)
    -- 0:unknown 1:textbefore, 2:textafter, 3:samepage
    local what = 0
    local li = internal(tag,n)
    if li then
        local metadata, pagenumber = li.metadata, li.pagenumber
        if metadata and pagenumber then
            local symbolpage = metadata.symbolpage or 0
            local notepage = pagenumber.number or 0
            if notepage > 0 and symbolpage > 0 then
                if notepage < symbolpage then
                    what = 1
                elseif notepage > symbolpage then
                    what = 2
                else
                    what = 3
                end
            end
        else
            -- might be a note that is not flushed due to to deep
            -- nesting in a vbox
            what = 3
        end
    end
    texwrite(what)
end

function notes.postpone()
    if trace_notes then
        logs.report("notes","postponing all insert notes")
    end
    for tag, state in next, notestates do
        if state.kind ~= "store" then
            notes.setstate(tag,"postpone")
        end
    end
end

function notes.setsymbolpage(tag,n)
    local nd = get(tag,n)
    if nd then
        nd.metadata.symbolpage = texcount.realpageno
    end
end

function notes.getsymbolpage(tag,n)
    local nd = get(tag,n)
    nd = nd and nd.metadata.symbolpage
    texwrite(nd or 0)
end

function notes.getnumberpage(tag,n)
    local li = internal(tag,n)
    li = li and li.pagenumber
    li = li and li.numbers
    li = li and li[1]
    texwrite(li or 0)
end

function notes.flush(tag,whatkind) -- store and postpone
    local state = notestates[tag]
    local kind = state.kind
    if kind == whatkind then
        local nd = notedata[tag]
        local ns = state.start -- first index
        if kind == "postpone" then
            if nd and ns then
                if trace_notes then
                    logs.report("notes","flushing state %s of %s from %s to %s",whatkind,tag,ns,#nd)
                end
                for i=ns,#nd do
                    texsprint(ctxcatcodes,format("\\handlenoteinsert{%s}{%s}",tag,i))
                end
            end
            state.start = nil
            state.kind = "insert"
        elseif kind == "store" then
            if nd and ns then
                if trace_notes then
                    logs.report("notes","flushing state %s of %s from %s to %s",whatkind,tag,ns,#nd)
                end
                for i=ns,#nd do
                    texsprint(ctxcatcodes,format("\\handlenoteitself{%s}{%s}",tag,i))
                end
            end
            state.start = nil
        elseif kind == "reset" then
            if nd and ns then
                if trace_notes then
                    logs.report("notes","flushing state %s of %s from %s to %s",whatkind,tag,ns,#nd)
                end
            end
            state.start = nil
        elseif trace_notes then
            logs.report("notes","not flushing state %s of %s",whatkind,tag)
        end
    elseif trace_notes then
        logs.report("notes","not flushing state %s of %s",whatkind,tag)
    end
end

function notes.flushpostponed()
    if trace_notes then
        logs.report("notes","flushing all postponed notes")
    end
    for tag, _ in next, notestates do
        notes.flush(tag,"postpone")
    end
end

function notes.resetpostponed()
    if trace_notes then
        logs.report("notes","resetting all postponed notes")
    end
    for tag, state in next, notestates do
        if state.kind == "postpone" then
            state.start = nil
            state.kind = "insert"
        end
    end
end

function notes.title(tag,n)
    structure.lists.savedtitle(tag,notedata[tag][n])
end

function notes.number(tag,n,spec)
    structure.lists.savedprefixednumber(tag,notedata[tag][n])
end