path: root/Master/texmf-dist/tex/context/base/strc-ref.lua

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

-- beware, this is a first step in the rewrite (just getting rid of
-- the tuo file); later all access and parsing will also move to lua

-- the useddata and pagedata names might change
-- todo: pack exported data

-- todo: autoload components when :::

local format, find, gmatch, match, concat = string.format, string.find, string.gmatch, string.match, table.concat
local texcount, texsetcount = tex.count, tex.setcount
local rawget, tonumber = rawget, tonumber
local lpegmatch = lpeg.match
local copytable = table.copy
local formatters = string.formatters

local allocate           = utilities.storage.allocate
local mark               = utilities.storage.mark
local setmetatableindex  = table.setmetatableindex

local trace_referencing  = false  trackers.register("structures.referencing",             function(v) trace_referencing = v end)
local trace_analyzing    = false  trackers.register("structures.referencing.analyzing",   function(v) trace_analyzing   = v end)
local trace_identifying  = false  trackers.register("structures.referencing.identifying", function(v) trace_identifying = v end)
local trace_importing    = false  trackers.register("structures.referencing.importing",   function(v) trace_importing   = v end)
local trace_empty        = false  trackers.register("structures.referencing.empty",       function(v) trace_empty       = v end)

local check_duplicates   = true

directives.register("structures.referencing.checkduplicates", function(v)
    check_duplicates = v
end)

local report_references  = logs.reporter("references")
local report_unknown     = logs.reporter("references","unknown")
local report_identifying = logs.reporter("references","identifying")
local report_importing   = logs.reporter("references","importing")
local report_empty       = logs.reporter("references","empty")

local variables          = interfaces.variables
local constants          = interfaces.constants
local context            = context

local v_default          = variables.default
local v_url              = variables.url
local v_file             = variables.file
local v_unknown          = variables.unknown
local v_yes              = variables.yes

local texcount           = tex.count
local texconditionals    = tex.conditionals

local productcomponent   = resolvers.jobs.productcomponent
local justacomponent     = resolvers.jobs.justacomponent

local logsnewline        = logs.newline
local logspushtarget     = logs.pushtarget
local logspoptarget      = logs.poptarget

local settings_to_array  = utilities.parsers.settings_to_array
local unsetvalue         = attributes.unsetvalue

local structures         = structures
local helpers            = structures.helpers
local sections           = structures.sections
local references         = structures.references
local lists              = structures.lists
local counters           = structures.counters

-- some might become local

references.defined       = references.defined or allocate()

local defined            = references.defined
local derived            = allocate()
local specials           = allocate()
local runners            = allocate()
local internals          = allocate()
local filters            = allocate()
local executers          = allocate()
local handlers           = allocate()
local tobesaved          = allocate()
local collected          = allocate()
local tobereferred       = allocate()
local referred           = allocate()

references.derived       = derived
references.specials      = specials
references.runners       = runners
references.internals     = internals
references.filters       = filters
references.executers     = executers
references.handlers      = handlers
references.tobesaved     = tobesaved
references.collected     = collected
references.tobereferred  = tobereferred
references.referred      = referred

local splitreference     = references.splitreference
local splitprefix        = references.splitcomponent -- replaces: references.splitprefix
local prefixsplitter     = references.prefixsplitter
local componentsplitter  = references.componentsplitter

local currentreference   = nil

storage.register("structures/references/defined", references.defined, "structures.references.defined")

local initializers = { }
local finalizers   = { }

function references.registerinitializer(func) -- we could use a token register instead
    initializers[#initializers+1] = func
end
function references.registerfinalizer(func) -- we could use a token register instead
    finalizers[#finalizers+1] = func
end

local function initializer() -- can we use a tobesaved as metatable for collected?
    tobesaved = references.tobesaved
    collected = references.collected
    for i=1,#initializers do
        initializers[i](tobesaved,collected)
    end
end

local function finalizer()
    for i=1,#finalizers do
        finalizers[i](tobesaved)
    end
end

job.register('structures.references.collected', tobesaved, initializer, finalizer)

local maxreferred = 1
local nofreferred = 0

-- local function initializer() -- can we use a tobesaved as metatable for collected?
--     tobereferred = references.tobereferred
--     referred     = references.referred
--     nofreferred = #referred
-- end

local function initializer() -- can we use a tobesaved as metatable for collected?
    tobereferred = references.tobereferred
    referred     = references.referred
    setmetatableindex(referred,get) -- hm, what is get ?
end

-- We make the array sparse (maybe a finalizer should optionally return a table) because
-- there can be quite some page links involved. We only store one action number per page
-- which is normally good enough for what we want (e.g. see above/below) and we do
-- a combination of a binary search and traverse backwards. A previous implementation
-- always did a traverse and was pretty slow on a large number of links (given that this
-- methods was used). It took me about a day to locate this as a bottleneck in processing
-- a 2500 page interactive document with 60 links per page. In that case, traversing
-- thousands of slots per link then brings processing to a grinding halt (especially when
-- there are no slots at all, which is the case in a first run).

local sparsetobereferred = { }

local function finalizer()
    local lastr, lasti
    local n = 0
    for i=1,maxreferred do
        local r = tobereferred[i]
        if not lastr then
            lastr = r
            lasti = i
        elseif r ~= lastr then
            n = n + 1
            sparsetobereferred[n] = { lastr, lasti }
            lastr = r
            lasti = i
        end
    end
    if lastr then
        n = n + 1
        sparsetobereferred[n] = { lastr, lasti }
    end
end

job.register('structures.references.referred', sparsetobereferred, initializer, finalizer)

local function referredpage(n)
    local max = nofreferred
    if max > 0 then
        -- find match
        local min = 1
        while true do
            local mid = floor((min+max)/2)
            local r = referred[mid]
            local m = r[2]
            if n == m then
                return r[1]
            elseif n > m then
                min = mid + 1
            else
                max = mid - 1
            end
            if min > max then
                break
            end
        end
        -- find first previous
        for i=min,1,-1 do
            local r = referred[i]
            if r and r[2] < n then
                return r[1]
            end
        end
    end
    -- fallback
    return texcount.realpageno
end

references.referredpage = referredpage

function references.registerpage(n) -- called in the backend code
    if not tobereferred[n] then
        if n > maxreferred then
            maxreferred = n
        end
        tobereferred[n] = texcount.realpageno
    end
end

-- todo: delay split till later as in destinations we split anyway

local orders, lastorder = { }, 0

local function setnextorder(kind,name)
    lastorder = 0
    if kind and name then
        local ok = orders[kind]
        if not ok then
            ok = { }
            orders[kind] = ok
        end
        lastorder = (ok[name] or 0) + 1
        ok[name] = lastorder
    end
    texsetcount("global","locationorder",lastorder)
end

references.setnextorder = setnextorder

function references.setnextinternal(kind,name)
    setnextorder(kind,name) -- always incremented with internal
    local n = texcount.locationcount + 1
    texsetcount("global","locationcount",n)
    return n
end

function references.currentorder(kind,name)
    return orders[kind] and orders[kind][name] or lastorder
end

local function setcomponent(data)
    -- we might consider doing this at the tex end, just like prefix
    local component = productcomponent()
    if component then
        local references = data and data.references
        if references then
            references.component = component
        end
        return component
    end
    -- but for the moment we do it here (experiment)
end

commands.setnextinternalreference = references.setnextinternal

function commands.currentreferenceorder(kind,name)
    context(references.currentorder(kind,name))
end

references.setcomponent = setcomponent

function references.set(kind,prefix,tag,data)
--  setcomponent(data)
    local pd = tobesaved[prefix] -- nicer is a metatable
    if not pd then
        pd = { }
        tobesaved[prefix] = pd
    end
    local n = 0
    for ref in gmatch(tag,"[^,]+") do
        if ref ~= "" then
            if check_duplicates and pd[ref] then
                if prefix and prefix ~= "" then
                    report_references("redundant reference %a in namespace %a",ref,prefix)
                else
                    report_references("redundant reference %a",ref)
                end
            else
                n = n + 1
                pd[ref] = data
                context.dofinishsomereference(kind,prefix,ref)
            end
        end
    end
    return n > 0
end

function references.enhance(prefix,tag)
    local l = tobesaved[prefix][tag]
    if l then
        l.references.realpage = texcount.realpageno
    end
end

commands.enhancereference = references.enhance

-- -- -- related to strc-ini.lua -- -- --

references.resolvers = references.resolvers or { }
local resolvers = references.resolvers

local function getfromlist(var)
    local vi = var.i
    if vi then
        vi = vi[3] or lists.collected[vi[2]]
        if vi then
            local r = vi.references and vi.references
            if r then
                r = r.realpage
            end
            if not r then
                r = vi.pagedata and vi.pagedata
                if r then
                    r = r.realpage
                end
            end
            var.i = vi
            var.r = r or 1
        else
            var.i = nil
            var.r = 1
        end
    else
        var.i = nil
        var.r = 1
    end
end

-- resolvers.section     = getfromlist
-- resolvers.float       = getfromlist
-- resolvers.description = getfromlist
-- resolvers.formula     = getfromlist
-- resolvers.note        = getfromlist

setmetatableindex(resolvers,function(t,k)
    local v = getfromlist
    resolvers[k] = v
    return v
end)

function resolvers.reference(var)
    local vi = var.i[2] -- check
    if vi then
        var.i = vi
        var.r = (vi.references and vi.references.realpage) or (vi.pagedata and vi.pagedata.realpage) or 1
    else
        var.i = nil
        var.r = 1
    end
end

local function register_from_lists(collected,derived,pages,sections)
    local g = derived[""] if not g then g = { } derived[""] = g end -- global
    for i=1,#collected do
        local entry = collected[i]
        local m, r = entry.metadata, entry.references
        if m and r then
            local reference = r.reference or ""
            local prefix = r.referenceprefix or ""
            local component = r.component and r.component or ""
            if reference ~= "" then
                local kind, realpage = m.kind, r.realpage
                if kind and realpage then
                    local d = derived[prefix]
                    if not d then
                        d = { }
                        derived[prefix] = d
                    end
                    local c = derived[component]
                    if not c then
                        c = { }
                        derived[component] = c
                    end
                    local t = { kind, i, entry }
                    for s in gmatch(reference,"%s*([^,]+)") do
                        if trace_referencing then
                            report_references("list entry %a provides %a reference %a on realpage %a",i,kind,s,realpage)
                        end
                        c[s] = c[s] or t -- share them
                        d[s] = d[s] or t -- share them
                        g[s] = g[s] or t -- first wins
                    end
                end
            end
        end
    end
--     inspect(derived)
end

references.registerinitializer(function() register_from_lists(lists.collected,derived) end)

-- urls

references.urls      = references.urls      or { }
references.urls.data = references.urls.data or { }

local urls = references.urls.data

function references.urls.define(name,url,file,description)
    if name and name ~= "" then
        urls[name] = { url or "", file or "", description or url or file or ""}
    end
end

local pushcatcodes = context.pushcatcodes
local popcatcodes  = context.popcatcodes
local txtcatcodes  = catcodes.numbers.txtcatcodes -- or just use "txtcatcodes"

function references.urls.get(name)
    local u = urls[name]
    if u then
        local url, file = u[1], u[2]
        if file and file ~= "" then
            return formatters["%s/%s"](url,file)
        else
            return url
        end
    end
end

function commands.geturl(name)
    local url = references.urls.get(name)
    if url and url ~= "" then
        pushcatcodes(txtcatcodes)
        context(url)
        popcatcodes()
    end
end

-- function commands.gethyphenatedurl(name,...)
--     local url = references.urls.get(name)
--     if url and url ~= "" then
--         hyphenatedurl(url,...)
--     end
-- end

function commands.doifurldefinedelse(name)
    commands.doifelse(urls[name])
end

commands.useurl= references.urls.define

-- files

references.files      = references.files      or { }
references.files.data = references.files.data or { }

local files = references.files.data

function references.files.define(name,file,description)
    if name and name ~= "" then
        files[name] = { file or "", description or file or "" }
    end
end

function references.files.get(name,method,space) -- method: none, before, after, both, space: yes/no
    local f = files[name]
    if f then
        context(f[1])
    end
end

function commands.doiffiledefinedelse(name)
    commands.doifelse(files[name])
end

commands.usefile= references.files.define

-- helpers

function references.checkedfile(whatever) -- return whatever if not resolved
    if whatever then
        local w = files[whatever]
        if w then
            return w[1]
        else
            return whatever
        end
    end
end

function references.checkedurl(whatever) -- return whatever if not resolved
    if whatever then
        local w = urls[whatever]
        if w then
            local u, f = w[1], w[2]
            if f and f ~= "" then
                return u .. "/" .. f
            else
                return u
            end
        else
            return whatever
        end
    end
end

function references.checkedfileorurl(whatever,default) -- return nil, nil if not resolved
    if whatever then
        local w = files[whatever]
        if w then
            return w[1], nil
        else
            local w = urls[whatever]
            if w then
                local u, f = w[1], w[2]
                if f and f ~= "" then
                    return nil, u .. "/" .. f
                else
                    return nil, u
                end
            end
        end
    end
    return default
end

-- programs

references.programs      = references.programs      or { }
references.programs.data = references.programs.data or { }

local programs = references.programs.data

function references.programs.define(name,file,description)
    if name and name ~= "" then
        programs[name] = { file or "", description or file or ""}
    end
end

function references.programs.get(name)
    local f = programs[name]
    return f and f[1]
end

function references.checkedprogram(whatever) -- return whatever if not resolved
    if whatever then
        local w = programs[whatever]
        if w then
            return w[1]
        else
            return whatever
        end
    end
end

commands.defineprogram = references.programs.define

function commands.getprogram(name)
    local f = programs[name]
    if f then
        context(f[1])
    end
end

-- shared by urls and files

function references.whatfrom(name)
    context((urls[name] and v_url) or (files[name] and v_file) or v_unknown)
end

function references.from(name)
    local u = urls[name]
    if u then
        local url, file, description = u[1], u[2], u[3]
        if description ~= "" then
            return description
            -- ok
        elseif file and file ~= "" then
            return url .. "/" .. file
        else
            return url
        end
    else
        local f = files[name]
        if f then
            local file, description = f[1], f[2]
            if description ~= "" then
                return description
            else
                return file
            end
        end
    end
end

function commands.from(name)
    local u = urls[name]
    if u then
        local url, file, description = u[1], u[2], u[3]
        if description ~= "" then
            context.dofromurldescription(description)
            -- ok
        elseif file and file ~= "" then
            context.dofromurlliteral(url .. "/" .. file)
        else
            context.dofromurlliteral(url)
        end
    else
        local f = files[name]
        if f then
            local file, description = f[1], f[2]
            if description ~= "" then
                context.dofromfiledescription(description)
            else
                context.dofromfileliteral(file)
            end
        end
    end
end

function references.define(prefix,reference,list)
    local d = defined[prefix] if not d then d = { } defined[prefix] = d end
    d[reference] = { "defined", list }
end

function references.reset(prefix,reference)
    local d = defined[prefix]
    if d then
        d[reference] = nil
    end
end

commands.definereference = references.define
commands.resetreference  = references.reset

-- \primaryreferencefoundaction
-- \secondaryreferencefoundaction
-- \referenceunknownaction

-- t.special t.operation t.arguments t.outer t.inner

-- to what extend do we check the non prefixed variant

local strict = false

local function resolve(prefix,reference,args,set) -- we start with prefix,reference
    if reference and reference ~= "" then
        if not set then
            set = { prefix = prefix, reference = reference }
        else
            set.reference = set.reference or reference
            set.prefix    = set.prefix    or prefix
        end
        local r = settings_to_array(reference)
        for i=1,#r do
            local ri = r[i]
            local d
            if strict then
                d = defined[prefix] or defined[""]
                d = d and d[ri]
            else
                d = defined[prefix]
                d = d and d[ri]
                if not d then
                    d = defined[""]
                    d = d and d[ri]
                end
            end
            if d then
                resolve(prefix,d[2],nil,set)
            else
                local var = splitreference(ri)
                if var then
                    var.reference = ri
                    local vo, vi = var.outer, var.inner
                    if not vo and vi then
                        -- to be checked
                        if strict then
                            d = defined[prefix] or defined[""]
                            d = d and d[vi]
                        else
                            d = defined[prefix]
                            d = d and d[vi]
                            if not d then
                                d = defined[""]
                                d = d and d[vi]
                            end
                        end
                        --
                        if d then
                            resolve(prefix,d[2],var.arguments,set) -- args can be nil
                        else
                            if args then var.arguments = args end
                            set[#set+1] = var
                        end
                    else
                        if args then var.arguments = args end
                        set[#set+1] = var
                    end
                    if var.has_tex then
                        set.has_tex = true
                    end
                else
                --  report_references("funny pattern %a",ri)
                end
            end
        end
        return set
    else
        return { }
    end
end

-- prefix == "" is valid prefix which saves multistep lookup

references.currentset = nil

function commands.setreferenceoperation(k,v)
    references.currentset[k].operation = v
end

function commands.setreferencearguments(k,v)
    references.currentset[k].arguments = v
end

local expandreferenceoperation = context.expandreferenceoperation
local expandreferencearguments = context.expandreferencearguments

function references.expandcurrent() -- todo: two booleans: o_has_tex& a_has_tex
    local currentset = references.currentset
    if currentset and currentset.has_tex then
        for i=1,#currentset do
            local ci = currentset[i]
            local operation = ci.operation
            if operation and find(operation,"\\") then -- if o_has_tex then
                expandreferenceoperation(i,operation)
            end
            local arguments = ci.arguments
            if arguments and find(arguments,"\\") then -- if a_has_tex then
                expandreferencearguments(i,arguments)
            end
        end
    end
end

commands.expandcurrentreference = references.expandcurrent -- for the moment the same

local externals = { }

-- we have prefixes but also components:
--
-- :    prefix
-- ::   always external
-- :::  internal (for products) or external (for components)

local function loadexternalreferences(name,utilitydata)
    local struc = utilitydata.structures
    if struc then
        local external = struc.references.collected -- direct references
        local lists    = struc.lists.collected      -- indirect references (derived)
        local pages    = struc.pages.collected      -- pagenumber data
        -- a bit weird one, as we don't have the externals in the collected
        for prefix, set in next, external do
            for reference, data in next, set do
                if trace_importing then
                    report_importing("registering %a reference, kind %a, name %a, prefix %a, reference %a",
                        "external","regular",name,prefix,reference)
                end
                local section  = reference.section
                local realpage = reference.realpage
                if section then
                    reference.sectiondata = lists[section]
                end
                if realpage then
                    reference.pagedata = pages[realpage]
                end
            end
        end
        for i=1,#lists do
            local entry      = lists[i]
            local metadata   = entry.metadata
            local references = entry.references
            if metadata and references then
                local reference = references.reference
                if reference and reference ~= "" then
                    local kind     = metadata.kind
                    local realpage = references.realpage
                    if kind and realpage then
                        references.pagedata = pages[realpage]
                        local prefix = references.referenceprefix or ""
                        local target = external[prefix]
                        if not target then
                            target = { }
                            external[prefix] = target
                        end
                        for s in gmatch(reference,"%s*([^,]+)") do
                            if trace_importing then
                                report_importing("registering %s reference, kind %a, name %a, prefix %a, reference %a",
                                    "external",kind,name,prefix,s)
                            end
                            target[s] = target[s] or entry
                        end
                    end
                end
            end
        end
        externals[name] = external
        return external
    end
end

local externalfiles = { }

table.setmetatableindex(externalfiles, function(t,k)
    local v = files[k]
    if not v then
        v = { k, k }
    end
    externalfiles[k] = v
    return v
end)

table.setmetatableindex(externals,function(t,k) -- either or not automatically
    local filename = externalfiles[k][1] -- filename
    local fullname = file.replacesuffix(filename,"tuc")
    if lfs.isfile(fullname) then -- todo: use other locator
        local utilitydata = job.loadother(fullname)
        if utilitydata then
            local external = loadexternalreferences(k,utilitydata)
            t[k] = external or false
            return external
        end
    end
    t[k] = false
    return false
end)

local productdata = allocate {
    productreferences   = { },
    componentreferences = { },
    components          = { },
}

references.productdata = productdata

local function loadproductreferences(productname,componentname,utilitydata)
    local struc = utilitydata.structures
    if struc then
        local productreferences = struc.references.collected -- direct references
        local lists = struc.lists.collected      -- indirect references (derived)
        local pages = struc.pages.collected      -- pagenumber data
        -- we use indirect tables to save room but as they are eventually
        -- just references we resolve them to data here (the mechanisms
        -- that use this data check for indirectness)
        for prefix, set in next, productreferences do
            for reference, data in next, set do
                if trace_importing then
                    report_importing("registering %s reference, kind %a, name %a, prefix %a, reference %a",
                        "product","regular",productname,prefix,reference)
                end
                local section  = reference.section
                local realpage = reference.realpage
                if section then
                    reference.sectiondata = lists[section]
                end
                if realpage then
                    reference.pagedata = pages[realpage]
                end
            end
        end
        --
        local componentreferences = { }
        for i=1,#lists do
            local entry      = lists[i]
            local metadata   = entry.metadata
            local references = entry.references
            if metadata and references then
                local reference = references.reference
                if reference and reference ~= "" then
                    local kind     = metadata.kind
                    local realpage = references.realpage
                    if kind and realpage then
                        references.pagedata = pages[realpage]
                        local prefix    = references.referenceprefix or ""
                        local component = references.component
                        local ctarget, ptarget
                        if not component or component == componentname then
                            -- skip
                        else
                            -- one level up
                            local external = componentreferences[component]
                            if not external then
                                external = { }
                                componentreferences[component] = external
                            end
                            if component == prefix then
                                prefix = ""
                            end
                            ctarget = external[prefix]
                            if not ctarget then
                                ctarget = { }
                                external[prefix] = ctarget
                            end
                        end
                        ptarget = productreferences[prefix]
                        if not ptarget then
                            ptarget = { }
                            productreferences[prefix] = ptarget
                        end
                        for s in gmatch(reference,"%s*([^,]+)") do
                            if ptarget then
                                if trace_importing then
                                    report_importing("registering %s reference, kind %a, name %a, prefix %a, reference %a",
                                        "product",kind,productname,prefix,s)
                                end
                                ptarget[s] = ptarget[s] or entry
                            end
                            if ctarget then
                                if trace_importing then
                                    report_importing("registering %s reference, kind %a, name %a, prefix %a, referenc %a",
                                        "component",kind,productname,prefix,s)
                                end
                                ctarget[s] = ctarget[s] or entry
                            end
                        end
                    end
                end
            end
        end
        productdata.productreferences   = productreferences -- not yet used
        productdata.componentreferences = componentreferences
    end
end

local function loadproductvariables(product,component,utilitydata)
    local struc = utilitydata.structures
    if struc then
        local lists = struc.lists and struc.lists.collected
        if lists then
            local pages = struc.pages and struc.pages.collected
            for i=1,#lists do
                local li = lists[i]
                if li.metadata.kind == "section" and li.references.component == component then
                    local firstsection = li
                    if firstsection.numberdata then
                        local numbers = firstsection.numberdata.numbers
                        if numbers then
                            if trace_importing then
                                report_importing("initializing section number to %:t",numbers)
                            end
                            productdata.firstsection = firstsection
                            structures.documents.preset(numbers)
                        end
                    end
                    if pages and firstsection.references then
                        local firstpage = pages[firstsection.references.realpage]
                        local number = firstpage and firstpage.number
                        if number then
                            if trace_importing then
                                report_importing("initializing page number to %a",number)
                            end
                            productdata.firstpage = firstpage
                            counters.set("userpage",1,number)
                        end
                    end
                    break
                end
            end
        end
    end
end

local function componentlist(tree,target)
    local branches = tree and tree.branches
    if branches then
        for i=1,#branches do
            local branch = branches[i]
            local type = branch.type
            if type == "component" then
                if target then
                    target[#target+1] = branch.name
                else
                    target = { branch.name }
                end
            elseif type == "product" or type == "component" then
                target = componentlist(branch,target)
            end
        end
    end
    return target
end

local function loadproductcomponents(product,component,utilitydata)
    local job = utilitydata.job
    productdata.components = componentlist(job and job.structure and job.structure.collected) or { }
end

references.registerinitializer(function(tobesaved,collected)
    -- not that much related to tobesaved or collected
    productdata.components = componentlist(job.structure.collected) or { }
end)

function structures.references.loadpresets(product,component) -- we can consider a special components hash
    if product and component and product~= "" and component ~= "" and not productdata.product then -- maybe: productdata.filename ~= filename
        productdata.product = product
        productdata.component = component
        local fullname = file.replacesuffix(product,"tuc")
        if lfs.isfile(fullname) then -- todo: use other locator
            local utilitydata = job.loadother(fullname)
            if utilitydata then
                if trace_importing then
                    report_importing("loading references for component %a of product %a from %a",component,product,fullname)
                end
                loadproductvariables (product,component,utilitydata)
                loadproductreferences(product,component,utilitydata)
                loadproductcomponents(product,component,utilitydata)
             -- inspect(productdata)
            end
        end
    end
end

structures.references.productdata = productdata

local useproduct = commands.useproduct

if useproduct then

    function commands.useproduct(product)
        useproduct(product)
        if texconditionals.autocrossfilereferences then
            local component = justacomponent()
            if component then
                if trace_referencing or trace_importing then
                    report_references("loading presets for component %a of product %a",component,product)
                end
                structures.references.loadpresets(product,component)
            end
        end
    end

end

-- productdata.firstsection.numberdata.numbers
-- productdata.firstpage.number

local function report_identify_special(set,var,i,type)
    local reference = set.reference
    local prefix    = set.prefix or ""
    local special   = var.special
    local error     = var.error
    local kind      = var.kind
    if error then
        report_identifying("type %a, reference %a, index %a, prefix %a, special %a, error %a",type,reference,i,prefix,special,error)
    else
        report_identifying("type %a, reference %a, index %a, prefix %a, special %a, kind %a",type,reference,i,prefix,special,kind)
    end
end

local function report_identify_arguments(set,var,i,type)
    local reference = set.reference
    local prefix    = set.prefix or ""
    local arguments = var.arguments
    local error     = var.error
    local kind      = var.kind
    if error then
        report_identifying("type %a, reference %a, index %a, prefix %a, arguments %a, error %a",type,reference,i,prefix,arguments,error)
    else
        report_identifying("type %a, reference %a, index %a, prefix %a, arguments %a, kind %a",type,reference,i,prefix,arguments,kind)
    end
end

local function report_identify_outer(set,var,i,type)
    local reference = set.reference
    local prefix    = set.prefix or ""
    local outer     = var.outer
    local error     = var.error
    local kind      = var.kind
    if outer then
        if error then
            report_identifying("type %a, reference %a, index %a, prefix %a, outer %a, error %a",type,reference,i,prefix,outer,error)
        else
            report_identifying("type %a, reference %a, index %a, prefix %a, outer %a, kind %a",type,reference,i,prefix,outer,kind)
        end
    else
        if error then
            report_identifying("type %a, reference %a, index %a, prefix %a, error %a",type,reference,i,prefix,error)
        else
            report_identifying("type %a, reference %a, index %a, prefix %a, kind %a",type,reference,i,prefix,kind)
        end
    end
end

local function identify_special(set,var,i)
    local special = var.special
    local s = specials[special]
    if s then
        local outer     = var.outer
        local operation = var.operation
        local arguments = var.arguments
        if outer then
            if operation then
                -- special(outer::operation)
                var.kind = "special outer with operation"
            else
                -- special()
                var.kind = "special outer"
            end
            var.f = outer
        elseif operation then
            if arguments then
                -- special(operation{argument,argument})
                var.kind = "special operation with arguments"
            else
                -- special(operation)
                var.kind = "special operation"
            end
        else
            -- special()
            var.kind = "special"
        end
        if trace_identifying then
            report_identify_special(set,var,i,"1a")
        end
    else
        var.error = "unknown special"
    end
    return var
end

local function identify_arguments(set,var,i)
    local s = specials[var.inner]
    if s then
        -- inner{argument}
        var.kind = "special with arguments"
    else
        var.error = "unknown inner or special"
    end
    if trace_identifying then
        report_identify_arguments(set,var,i,"3a")
    end
    return var
end

local function identify_inner(set,var,prefix,collected,derived,tobesaved)
    local inner = var.inner
    local outer = var.outer
    -- inner ... we could move the prefix logic into the parser so that we have 'm for each entry
    -- foo:bar -> foo == prefix (first we try the global one)
    -- -:bar   -> ignore prefix
    local p, i = prefix, nil
    local splitprefix, splitinner
    -- the next test is a safeguard when references are auto loaded from outer
    if inner then
        splitprefix, splitinner = lpegmatch(prefixsplitter,inner)
    end
    -- these are taken from other anonymous references
    if splitprefix and splitinner then
        if splitprefix == "-" then
            i = collected[""]
            i = i and i[splitinner]
            if i then
                p = ""
            end
        else
            i = collected[splitprefix]
            i = i and i[splitinner]
            if i then
                p = splitprefix
            end
        end
    end
    -- todo: strict here
    if not i then
        i = collected[prefix]
        i = i and i[inner]
        if i then
            p = prefix
        end
    end
    if not i and prefix ~= "" then
        i = collected[""]
        i = i and i[inner]
        if i then
            p = ""
        end
    end
    if i then
        var.i = { "reference", i }
        resolvers.reference(var)
        var.kind = "inner"
        var.p = p
    elseif derived then
        -- these are taken from other data structures (like lists)
        if splitprefix and splitinner then
            if splitprefix == "-" then
                i = derived[""]
                i = i and i[splitinner]
                if i then
                    p = ""
                end
            else
                i = derived[splitprefix]
                i = i and i[splitinner]
                if i then
                    p = splitprefix
                end
            end
        end
        if not i then
            i = derived[prefix]
            i = i and i[inner]
            if i then
                p = prefix
            end
        end
        if not i and prefix ~= "" then
            i = derived[""]
            i = i and i[inner]
            if i then
                p = ""
            end
        end
        if i then
            var.kind = "inner"
            var.i = i
            var.p = p
            local ri = resolvers[i[1]]
            if ri then
                ri(var)
            else
                -- can't happen as we catch it with a metatable now
                report_references("unknown inner resolver for %a",i[1])
            end
        else
            -- no prefixes here
            local s = specials[inner]
            if s then
                var.kind = "special"
            else
                i = (collected and collected[""] and collected[""][inner]) or
                    (derived   and derived  [""] and derived  [""][inner]) or
                    (tobesaved and tobesaved[""] and tobesaved[""][inner])
                if i then
                    var.kind = "inner"
                    var.i = { "reference", i }
                    resolvers.reference(var)
                    var.p = ""
                else
                    var.error = "unknown inner or special"
                end
            end
        end
    end
    return var
end

local function identify_outer(set,var,i)
    local outer    = var.outer
    local inner    = var.inner
    local external = externals[outer]
    if external then
        local v = copytable(var)
        v = identify_inner(set,v,nil,external)
        if v.i and not v.error then
            v.kind = "outer with inner"
            set.external = true
            if trace_identifying then
                report_identify_outer(set,v,i,"2a")
            end
            return v
        end
        v = copytable(var)
        local v = identify_inner(set,v,v.outer,external)
        if v.i and not v.error then
            v.kind = "outer with inner"
            set.external = true
            if trace_identifying then
                report_identify_outer(set,v,i,"2b")
            end
            return v
        end
    end
    local external = productdata.componentreferences[outer]
    if external then
        local v = identify_inner(set,copytable(var),nil,external)
        if v.i and not v.error then
            v.kind = "outer with inner"
            set.external = true
            if trace_identifying then
                report_identify_outer(set,v,i,"2c")
            end
            return v
        end
    end
    local external = productdata.productreferences[outer]
    if external then
        local vi = external[inner]
        if vi then
            var.kind = "outer with inner"
            var.i = vi
            set.external = true
            if trace_identifying then
                report_identify_outer(set,var,i,"2d")
            end
            return var
        end
    end
    -- the rest
    local special   = var.special
    local arguments = var.arguments
    local operation = var.operation
    if inner then
        if arguments then
            -- outer::inner{argument}
            var.kind = "outer with inner with arguments"
        else
            -- outer::inner
            var.kind = "outer with inner"
        end
        var.i = { "reference", inner }
        resolvers.reference(var)
        var.f = outer
        if trace_identifying then
            report_identify_outer(set,var,i,"2e")
        end
    elseif special then
        local s = specials[special]
        if s then
            if operation then
                if arguments then
                    -- outer::special(operation{argument,argument})
                    var.kind = "outer with special and operation and arguments"
                else
                    -- outer::special(operation)
                    var.kind = "outer with special and operation"
                end
            else
                -- outer::special()
                var.kind = "outer with special"
            end
            var.f = outer
        else
            var.error = "unknown outer with special"
        end
        if trace_identifying then
            report_identify_outer(set,var,i,"2f")
        end
    else
        -- outer::
        var.kind = "outer"
        var.f = outer
        if trace_identifying then
            report_identify_outer(set,var,i,"2g")
        end
    end
    return var
end

local function identify_inner_or_outer(set,var,i)
    -- here we fall back on product data
    local inner = var.inner
    if inner and inner ~= "" then
        local v = identify_inner(set,copytable(var),set.prefix,collected,derived,tobesaved)
        if v.i and not v.error then
            v.kind = "inner" -- check this
            if trace_identifying then
                report_identify_outer(set,v,i,"4a")
            end
            return v
        end

local components = job.structure.components

if components then
    for i=1,#components do
        local component = components[i]
        local data = collected[component]
        local vi = data and data[inner]
        if vi then
            var.outer = component
            var.i = vi
            var.kind = "outer with inner"
            set.external = true
            if trace_identifying then
                report_identify_outer(set,var,i,"4x")
            end
            return var
        end
    end
end

        local componentreferences = productdata.componentreferences
        local productreferences = productdata.productreferences
        local components = productdata.components
        if components and componentreferences then
         -- for component, data in next, productdata.componentreferences do -- better do this in order of processing:
            for i=1,#components do
                local component = components[i]
                local data = componentreferences[component]
                if data then
                    local d = data[""]
                    local vi = d and d[inner]
                    if vi then
                        var.outer = component
                        var.i = vi
                        var.kind = "outer with inner"
                        set.external = true
                        if trace_identifying then
                            report_identify_outer(set,var,i,"4b")
                        end
                        return var
                    end
                end
            end
        end
        local component, inner = lpegmatch(componentsplitter,inner)
        if component then
            local data = componentreferences and componentreferences[component]
            if data then
                local d = data[""]
                local vi = d and d[inner]
                if vi then
                    var.inner = inner
                    var.outer = component
                    var.i = vi
                    var.kind = "outer with inner"
                    set.external = true
                    if trace_identifying then
                        report_identify_outer(set,var,i,"4c")
                    end
                    return var
                end
            end
            local data = productreferences and productreferences[component]
            if data then
                local vi = data[inner]
                if vi then
                    var.inner = inner
                    var.outer = component
                    var.i = vi
                    var.kind = "outer with inner"
                    set.external = true
                    if trace_identifying then
                        report_identify_outer(set,var,i,"4d")
                    end
                    return var
                end
            end
        end
        var.error = "unknown inner"
    else
        var.error = "no inner"
    end
    if trace_identifying then
        report_identify_outer(set,var,i,"4e")
    end
    return var
end

-- local function identify_inner_or_outer(set,var,i)
--     -- we might consider first checking with a prefix prepended and then without
--     -- which is better for fig:oeps
--     local var = do_identify_inner_or_outer(set,var,i)
--     if var.error then
--         local prefix = set.prefix
--         if prefix and prefix ~= "" then
--             var.inner = prefix .. ':' .. var.inner
--             var.error = nil
--             return do_identify_inner_or_outer(set,var,i)
--         end
--     end
--     return var
-- end

local function identify_inner_component(set,var,i)
    -- we're in a product (maybe ignore when same as component)
    local component = var.component
    identify_inner(set,var,component,collected,derived,tobesaved)
    if trace_identifying then
        report_identify_outer(set,var,i,"5a")
    end
    return var
end

local function identify_outer_component(set,var,i)
    local component = var.component
    local inner = var.inner
    local data = productdata.componentreferences[component]
    if data then
        local d = data[""]
        local vi = d and d[inner]
        if vi then
            var.inner = inner
            var.outer = component
            var.i = vi
            var.kind = "outer with inner"
            set.external = true
            if trace_identifying then
                report_identify_outer(set,var,i,"6a")
            end
            return var
        end
    end
    local data = productdata.productreferences[component]
    if data then
        local vi = data[inner]
        if vi then
            var.inner = inner
            var.outer = component
            var.i = vi
            var.kind = "outer with inner"
            set.external = true
            if trace_identifying then
                report_identify_outer(set,var,i,"6b")
            end
            return var
        end
    end
    var.error = "unknown component"
    if trace_identifying then
        report_identify_outer(set,var,i,"6c")
    end
    return var
end

local nofidentified = 0

local function identify(prefix,reference)
    if not reference then
        prefix    = ""
        reference = prefix
    end
    local set = resolve(prefix,reference)
    local bug = false
    texcount.referencehastexstate = set.has_tex and 1 or 0
    nofidentified = nofidentified + 1
    set.n = nofidentified
    for i=1,#set do
        local var = set[i]
        if var.special then
            var = identify_special(set,var,i)
        elseif var.outer then
            var = identify_outer(set,var,i)
        elseif var.arguments then
            var = identify_arguments(set,var,i)
        elseif not var.component then
            var = identify_inner_or_outer(set,var,i)
        elseif productcomponent() then
            var = identify_inner_component(set,var,i)
        else
            var = identify_outer_component(set,var,i)
        end
        set[i] = var
        bug = bug or var.error
    end
    references.currentset = mark(set) -- mark, else in api doc
    if trace_analyzing then
        report_references(table.serialize(set,reference))
    end
    return set, bug
end

references.identify = identify

local unknowns, nofunknowns, f_valid = { }, 0, formatters["[%s][%s]"]

function references.valid(prefix,reference,highlight,newwindow,layer)
    local set, bug = identify(prefix,reference)
    local unknown = bug or #set == 0
    if unknown then
        currentreference = nil -- will go away
        local str = f_valid(prefix,reference)
        local u = unknowns[str]
        if not u then
            interfaces.showmessage("references",1,str) -- 1 = unknown, 4 = illegal
            unknowns[str] = 1
            nofunknowns = nofunknowns + 1
        else
            unknowns[str] = u + 1
        end
    else
        set.highlight, set.newwindow, set.layer = highlight, newwindow, layer
        currentreference = set[1]
    end
    -- we can do the expansion here which saves a call
    return not unknown
end

function commands.doifelsereference(prefix,reference,highlight,newwindow,layer)
    commands.doifelse(references.valid(prefix,reference,highlight,newwindow,layer))
end

function references.reportproblems() -- might become local
    if nofunknowns > 0 then
        statistics.register("cross referencing", function()
            return format("%s identified, %s unknown",nofidentified,nofunknowns)
        end)
        logspushtarget("logfile")
        logsnewline()
        report_references("start problematic references")
        logsnewline()
        for k, v in table.sortedpairs(unknowns) do
            report_unknown("%4i: %s",v,k)
        end
        logsnewline()
        report_references("stop problematic references")
        logsnewline()
        logspoptarget()
    end
end

luatex.registerstopactions(references.reportproblems)

local innermethod = "names"

function references.setinnermethod(m)
    if m then
        if m == "page" or m == "mixed" or m == "names" then
            innermethod = m
        elseif m == true or m == v_yes then
            innermethod = "page"
        end
    end
    function references.setinnermethod()
        report_references("inner method is already set and frozen to %a",innermethod)
    end
end

function references.getinnermethod()
    return innermethod or "names"
end

directives.register("references.linkmethod", function(v) -- page mixed names
    references.setinnermethod(v)
end)

-- this is inconsistent

function references.setinternalreference(prefix,tag,internal,view) -- needs checking
    if innermethod == "page" then
        return unsetvalue
    else
        local t, tn = { }, 0 -- maybe add to current
        if tag then
            if prefix and prefix ~= "" then
                prefix = prefix .. ":" -- watch out, : here
                for ref in gmatch(tag,"[^,]+") do
                    tn = tn + 1
                    t[tn] = prefix .. ref
                end
            else
                for ref in gmatch(tag,"[^,]+") do
                    tn = tn + 1
                    t[tn] = ref
                end
            end
        end
        if internal and innermethod == "names" then -- mixed or page
            tn = tn + 1
            t[tn] = "aut:" .. internal
        end
        local destination = references.mark(t,nil,nil,view) -- returns an attribute
        texcount.lastdestinationattribute = destination
        return destination
    end
end

function references.setandgetattribute(kind,prefix,tag,data,view) -- maybe do internal automatically here
    local attr = references.set(kind,prefix,tag,data) and references.setinternalreference(prefix,tag,nil,view) or unsetvalue
    texcount.lastdestinationattribute = attr
    return attr
end

commands.setreferenceattribute = references.setandgetattribute

function references.getinternalreference(n) -- n points into list (todo: registers)
    local l = lists.collected[n]
    return l and l.references.internal or n
end

function commands.setinternalreference(prefix,tag,internal,view) -- needs checking
    context(references.setinternalreference(prefix,tag,internal,view))
end

function commands.getinternalreference(n) -- this will also be a texcount
    local l = lists.collected[n]
    context(l and l.references.internal or n)
end

--

function references.getcurrentmetadata(tag)
    local data = currentreference and currentreference.i
    return data and data.metadata and data.metadata[tag]
end

function commands.getcurrentreferencemetadata(tag)
    local data = references.getcurrentmetadata(tag)
    if data then
        context(data)
    end
end

local function currentmetadata(tag)
    local data = currentreference and currentreference.i
    return data and data.metadata and data.metadata[tag]
end

references.currentmetadata = currentmetadata

local function getcurrentprefixspec(default)
    -- todo: message
    return currentmetadata("kind") or "?", currentmetadata("name") or "?", default or "?"
end

references.getcurrentprefixspec = getcurrentprefixspec

function commands.getcurrentprefixspec(default)
    context.getreferencestructureprefix(getcurrentprefixspec(default))
end

function references.filter(name,...) -- number page title ...
    local data = currentreference and currentreference.i -- maybe we should take realpage from here
    if data then
        if name == "realpage" then
            local cs = references.analyze() -- normally already analyzed but also sets state
            context(tonumber(cs.realpage) or 0) -- todo, return and in command namespace
        else -- assumes data is table
            local kind = type(data) == "table" and data.metadata and data.metadata.kind
            if kind then
                local filter = filters[kind] or filters.generic
                filter = filter and (filter[name] or filter.unknown or filters.generic[name] or filters.generic.unknown)
                if filter then
                    if trace_referencing then
                        report_references("name %a, kind %a, using dedicated filter",name,kind)
                    end
                    filter(data,name,...)
                elseif trace_referencing then
                    report_references("name %a, kind %a, using generic filter",name,kind)
                end
            elseif trace_referencing then
                report_references("name %a, unknown kind",name)
            end
        end
    elseif name == "realpage" then
        context(0)
    elseif trace_referencing then
        report_references("name %a, no reference",name)
    end
end

function references.filterdefault()
    return references.filter("default",getcurrentprefixspec(v_default))
end

function commands.currentreferencedefault(tag)
    if not tag then tag = "default" end
    references.filter(tag,context.delayed(getcurrentprefixspec(tag)))
end

filters.generic = { }

function filters.generic.title(data)
    if data then
        local titledata = data.titledata or data.useddata
        if titledata then
            helpers.title(titledata.title or "?",data.metadata)
        end
    end
end

function filters.generic.text(data)
    if data then
        local entries = data.entries or data.useddata
        if entries then
            helpers.title(entries.text or "?",data.metadata)
        end
    end
end

function filters.generic.number(data,what,prefixspec) -- todo: spec and then no stopper
    if data then
        numberdata = lists.reordered(data) -- data.numberdata
        if numberdata then
            helpers.prefix(data,prefixspec)
            sections.typesetnumber(numberdata,"number",numberdata)
        else
            local useddata = data.useddata
            if useddata and useddsta.number then
                context(useddata.number)
            end
        end
    end
end

filters.generic.default = filters.generic.text

function filters.generic.page(data,prefixspec,pagespec)
    local pagedata = data.pagedata
    if pagedata then
        local number, conversion = pagedata.number, pagedata.conversion
        if not number then
            -- error
        elseif conversion then
            context.convertnumber(conversion,number)
        else
            context(number)
        end
    else
        helpers.prefixpage(data,prefixspec,pagespec)
    end
end

filters.user = { }

function filters.user.unknown(data,name)
    if data then
        local userdata = data.userdata
        local userkind = userdata and userdata.kind
        if userkind then
            local filter = filters[userkind] or filters.generic
            filter = filter and (filter[name] or filter.unknown)
            if filter then
                filter(data,name)
                return
            end
        end
        local namedata = userdata and userdata[name]
        if namedata then
            context(namedata)
        end
    end
end

filters.text = { }

function filters.text.title(data)
    helpers.title(data.entries.text or "?",data.metadata)
end

-- no longer considered useful:
--
-- function filters.text.number(data)
--     helpers.title(data.entries.text or "?",data.metadata)
-- end

function filters.text.page(data,prefixspec,pagespec)
    helpers.prefixpage(data,prefixspec,pagespec)
end

filters.full = { }

filters.full.title = filters.text.title
filters.full.page  = filters.text.page

filters.section = { }

function filters.section.number(data,what,prefixspec)
    if data then
        local numberdata = data.numberdata
        if not numberdata then
            local useddata = data.useddata
            if useddata and useddata.number then
                context(useddata.number)
            end
        elseif numberdata.hidenumber then
            local references = data.references
            if trace_empty then
                report_empty("reference %a has a hidden number",references.reference)
                context.emptyreference() -- maybe an option
            end
        else
            sections.typesetnumber(numberdata,"number",prefixspec,numberdata)
        end
    end
end

filters.section.title   = filters.generic.title
filters.section.page    = filters.generic.page
filters.section.default = filters.section.number

-- filters.note        = { default = filters.generic.number }
-- filters.formula     = { default = filters.generic.number }
-- filters.float       = { default = filters.generic.number }
-- filters.description = { default = filters.generic.number }
-- filters.item        = { default = filters.generic.number }

setmetatableindex(filters, function(t,k) -- beware, test with rawget
    local v = { default = filters.generic.number } -- not copy as it might be extended differently
    t[k] = v
    return v
end)

-- function references.sectiontitle(n)
--     helpers.sectiontitle(lists.collected[tonumber(n) or 0])
-- end

-- function references.sectionnumber(n)
--     helpers.sectionnumber(lists.collected[tonumber(n) or 0])
-- end

-- function references.sectionpage(n,prefixspec,pagespec)
--     helpers.prefixedpage(lists.collected[tonumber(n) or 0],prefixspec,pagespec)
-- end

-- analyze

references.testrunners  = references.testrunners  or { }
references.testspecials = references.testspecials or { }

local runners  = references.testrunners
local specials = references.testspecials

-- We need to prevent ending up in the 'relative location' analyzer as it is
-- pretty slow (progressively). In the pagebody one can best check the reference
-- real page to determine if we need contrastlocation as that is more lightweight.

local function checkedpagestate(n,page)
    local r, p = referredpage(n), tonumber(page)
    if not p then
        return 0
    elseif p > r then
        return 3 -- after
    elseif p < r then
        return 2 -- before
    else
        return 1 -- same
    end
end

local function setreferencerealpage(actions)
    actions = actions or references.currentset
    if not actions then
        return 0
    else
        local realpage = actions.realpage
        if realpage then
            return realpage
        end
        local nofactions = #actions
        if nofactions > 0 then
            for i=1,nofactions do
                local a = actions[i]
                local what = runners[a.kind]
                if what then
                    what = what(a,actions) -- needs documentation
                end
            end
            realpage = actions.realpage
            if realpage then
                return realpage
            end
        end
        actions.realpage = 0
        return 0
    end
end

-- we store some analysis data alongside the indexed array
-- at this moment only the real reference page is analyzed
-- normally such an analysis happens in the backend code

function references.analyze(actions)
    actions = actions or references.currentset
    if not actions then
        actions = { realpage = 0, pagestate = 0 }
    elseif actions.pagestate then
        -- already done
    else
        local realpage = actions.realpage or setreferencerealpage(actions)
        if realpage == 0 then
            actions.pagestate = 0
        elseif actions.external then
            actions.pagestate = 0
        else
            actions.pagestate = checkedpagestate(actions.n,realpage)
        end
    end
    return actions
end

function commands.referencepagestate(actions)
    actions = actions or references.currentset
    if not actions then
        context(0)
    else
        if not actions.pagestate then
            references.analyze(actions) -- delayed unless explicitly asked for
        end
        context(actions.pagestate)
    end
end

function commands.referencerealpage(actions)
    actions = actions or references.currentset
    context(not actions and 0 or actions.realpage or setreferencerealpage(actions))
end

local plist, nofrealpages

local function realpageofpage(p) -- the last one counts !
    if not plist then
        local pages = structures.pages.collected
        nofrealpages = #pages
        plist = { }
        for rp=1,nofrealpages do
            plist[pages[rp].number] = rp
        end
        references.nofrealpages = nofrealpages
    end
    return plist[p]
end

references.realpageofpage = realpageofpage

function references.checkedrealpage(r)
    if not plist then
        realpageofpage(r) -- just initialize
    end
    if not r then
        return texcount.realpageno
    elseif r < 1 then
        return 1
    elseif r > nofrealpages then
        return nofrealpages
    else
        return r
    end
end

-- use local ?

local pages = allocate {
    [variables.firstpage]       = function() return counters.record("realpage")["first"]    end,
    [variables.previouspage]    = function() return counters.record("realpage")["previous"] end,
    [variables.nextpage]        = function() return counters.record("realpage")["next"]     end,
    [variables.lastpage]        = function() return counters.record("realpage")["last"]     end,

    [variables.firstsubpage]    = function() return counters.record("subpage" )["first"]    end,
    [variables.previoussubpage] = function() return counters.record("subpage" )["previous"] end,
    [variables.nextsubpage]     = function() return counters.record("subpage" )["next"]     end,
    [variables.lastsubpage]     = function() return counters.record("subpage" )["last"]     end,

    [variables.forward]         = function() return counters.record("realpage")["forward"]  end,
    [variables.backward]        = function() return counters.record("realpage")["backward"] end,
}

references.pages = pages

-- maybe some day i will merge this in the backend code with a testmode (so each
-- runner then implements a branch)

runners["inner"] = function(var,actions)
    local r = var.r
    if r then
        actions.realpage = r
    end
end

runners["special"] = function(var,actions)
    local handler = specials[var.special]
    return handler and handler(var,actions)
end

runners["special operation"]                = runners["special"]
runners["special operation with arguments"] = runners["special"]

-- These are the testspecials not the real ones. They are used to
-- check the validity.

function specials.internal(var,actions)
    local v = references.internals[tonumber(var.operation)]
    local r = v and v.references.realpage
    if r then
        actions.realpage = r
    end
end

specials.i = specials.internal

function specials.page(var,actions)
    local o = var.operation
    local p = pages[o]
    if type(p) == "function" then
        p = p()
    else
        p = tonumber(realpageofpage(tonumber(o)))
    end
    if p then
        var.r = p
        actions.realpage = actions.realpage or p -- first wins
    end
end

function specials.realpage(var,actions)
    local p = tonumber(var.operation)
    if p then
        var.r = p
        actions.realpage = actions.realpage or p -- first wins
    end
end

function specials.userpage(var,actions)
    local p = tonumber(realpageofpage(var.operation))
    if p then
        var.r = p
        actions.realpage = actions.realpage or p -- first wins
    end
end

function specials.deltapage(var,actions)
    local p = tonumber(var.operation)
    if p then
        p = references.checkedrealpage(p + texcount.realpageno)
        var.r = p
        actions.realpage = actions.realpage or p -- first wins
    end
end

function specials.section(var,actions)
    local sectionname = var.arguments
    local destination = var.operation
    local internal    = structures.sections.internalreference(sectionname,destination)
    if internal then
        var.special   = "internal"
        var.operation = internal
        var.arguments = nil
        specials.internal(var,actions)
    end
end

-- needs a better split ^^^

commands.filterreference        = references.filter
commands.filterdefaultreference = references.filterdefault

-- done differently now:

function references.export(usedname) end
function references.import(usedname) end
function references.load  (usedname) end

commands.exportreferences = references.export