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

local insert, remove, concat = table.insert, table.remove, table.concat
local find, format = string.find, string.format
local type, next = type, next
local round = math.round
local sortedhash, sortedkeys, tohash = table.sortedhash, table.sortedkeys, table.tohash

-- Callbacks are the real asset of LuaTeX. They permit you to hook your own code
-- into the TeX engine. Here we implement a few handy auxiliary functions. Watch
-- out, there are diferences between LuateX and LuaMetaTeX.

-- By now most callbacks are frozen and most provide a way to plug in your own code.
-- For instance all node list handlers provide before/after namespaces and the file
-- handling code can be extended by adding schemes and if needed I can add more
-- hooks. So there is no real need to overload a core callback function. The ability
-- to overload by a user (push/pop etc) has been removed. You can find the oveload
-- code in version before 2025-06-01.

callbacks       = callbacks or { }
local callbacks = callbacks

local trace_callbacks      = false  trackers.register("system.callbacks", function(v) trace_callbacks = v end)
local trace_checking       = false  trackers.register("memory.checking", function(v) trace_checking = v end)

local report_system        = logs.reporter("system")
local report_callbacks     = logs.reporter("system","callbacks")
local report_memory        = logs.reporter("system","memory")

local register_callback    = callback.register
local find_callback        = callback.find
local name_callbacks       = callback.names
local set_callback_state   = callback.setstate
local get_callback_state   = callback.getstate
local set_callback_options = callback.setoptions
local get_callback_index   = callback.getindex

local comments   = { }
local names      = callback.names()
local list       = table.swapped(names)

callbacks.names  = names -- index -> name
callbacks.list   = list  -- name  -> index

local optionbits = callback.getoptionvalues()
local statebits  = callback.getstatevalues()

local options    = table.swapped(optionbits,optionbits)
local states     = table.swapped(statebits,statebits)

callbacks.optioncodes = options
callbacks.statecodes  = states
callbacks.optionbits  = optionbits
callbacks.statebits   = statebits

local disabled_code <const> = states.disabled
local frozen_code   <const> = states.frozen

local trace_code    <const> = options.trace

callback.setoptions(options.direct) -- might become permanent

-- temporary, not public, needed in driv-ini and lua-run:

callbacks.functions = { }

trackers.register("callbacks.calls",function(v)
    set_callback_options(trace_code,v and true or false)
end)

local delayed = false  do
    if environment.initex then
        delayed = {
            "buildpage",
        }
        for i=1,#delayed do
            set_callback_state(delayed[i],disabled_code & frozen_code)
        end
        delayed = tohash(delayed)
    end
end

function callbacks.known(name)
    return find_callback(name)
end

function callbacks.freeze(name)
    if find(name,"*",1,true) then
        local pattern = name
        for name, index in next, list do
            if find(name,pattern) then
             -- set_callback_state(name,frozen_code)
                set_callback_state(index,frozen_code)
            end
        end
    else
        set_callback_state(name,frozen_code)
    end
end

-- For now we also support the old interface.

do

    local function register(specification,action,freeze)
        if type(specification) ~= "table" then
            specification = {
                name    = specification,
                action  = action,
                frozen  = freeze and true or false,
                comment = type(freeze) == "string" and freeze or nil,
            }
        end
        local name = specification.name
        if type(name) ~= "string" or name == "" then
            report_callbacks("bad callback registration %a","invalid name")
            return
        end
        if delayed and delayed[name] then
            return nil
        end
        local comment = specification.comment
        if type(comment) ~= "string" then
            comment = name
        end
        --
        local index = register_callback(name,specification.action or false)
        if index then
            if specification.disable or specification.disabled then
                set_callback_state(index,disabled_code)
            end
            if specification.freeze or specification.frozen then
                set_callback_state(index,frozen_code)
            end
        else
            report_callbacks("bad callback registration %a",name)
            os.exit()
        end
        --
        comments[index] = comment
        comments[name]  = comment
        --
        return index
    end

    callbacks.register = register

    function callback.register(name,action) -- original
        return register { name = name, action = action }
    end

end

function callbacks.optimizer(name)
    local index = get_callback_index(name)
    if index then
        return
            index,
            function() set_callback_state(index) end,
            function() set_callback_state(index,disabled_code) end
    end
end


function callbacks.push() end -- obsolete
function callbacks.pop () end -- obsolete

-- This will move to a module (but then i need to adapt a few manuals and
-- modules.

do

    local keys = false

    local function getstates(i)
        if not keys then
            keys = sortedkeys(statebits)
        end
        local state  = get_callback_state(i)
        local result = { }
        if state and state ~= 0 then
            for i=1,#keys do
                local k = keys[i]
                if (state & k) == k then
                    result[#result+1] = statebits[k]
                end
            end
        end
        return result
    end

    local function getcomment(name)
        return comments[name] or ""
    end

    callbacks.getstates  = getstates
    callbacks.getcomment = getcomment

    function callbacks.report()
        for name, index in sortedhash(list) do
            report_callbacks("%2i %-20s : [% t] %s",index,name,getstates(index),getcomment(com))
        end
    end

end