%D \module
%D   [      file=s-present-steps,
%D        version=2018.05.17,
%D          title=\CONTEXT\ Style File,
%D       subtitle=Presentation Environment Repeated Steps,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

%D This a preliminary module, a quick hack and not entirely proper \CONTEXT, but
%D let's see what more is needed.

\startmodule[present-steps]

\startluacode

moduledata.steps = moduledata.steps or { }

local steps      = moduledata.steps
local data       = { }
local name       = "unknown"
local set        = 0
local settings   = nil

function steps.startsteps(buffername)
    set  = set + 1
    data = { }
    name = buffername
end

function steps.stopsteps()
    local n = 0
    for i=1,#data do
        local state = "once"
        local done  = 0
        while true do
            context.startprocessingsteps()
            for j=1,i do
                local step    = data[j]
                local nested  = step.nested
                local content = step.content
                local last    = (i == #data) and (j == i) and 1 or 0
                local option = step.option
                local flush  = true
                if option == interfaces.variables["title"] then
                    if i > 1 then
                        flush = false
                    end
                elseif option == interfaces.variables["repeat"] then
                    if i == 1 then
                        flush = false
                    end
                end
                if flush then
                    if j < i or nested == 0 then
                        context(function()
                            buffers.assign("step",content)
                            context.processstep("step",i,0,last)
                         -- context.writestatus("step a",string.formatters["%i %i %i"](i,0,last))
                        end)
                        state = "done"
                    else
                        done = done + 1
                        local d = done
                        context(function()
                            buffers.assign("step",content)
                            context.processstep("step",i,d,last)
                         -- context.writestatus("step b",string.formatters["%i %i %i"](i,d,last))
                        end)
                        if done == nested then
                            state = "done"
                            n = n + nested
                        else
                            state = "busy"
                        end
                    end
                end
            end
            context.stopprocessingsteps()
            if state == "done" then
                break
            end
        end
    end
end

function steps.startstep(str)
    settings = utilities.parsers.settings_to_hash(str)
end

function steps.stopstep()
    settings.content = buffers.getcontent(name)
    settings.nested  = tonumber(settings.n) or 0
    data[#data+1] = settings
end

function steps.startsubstep(str)
    local d = data[#data]
    d.nested = d.nested + 1
end

function steps.stopsubstep()
end

\stopluacode

\definebuffer
  [step]

\def\currentstep   {0}
\def\currentsubstep{0}

\unexpanded\def\startprocessingsteps
  {\global\wantedsubstep\zerocount}

\unexpanded\def\stopprocessingsteps
  {}

\unexpanded\def\processstep#1#2#3#4%
  {\par
   \edef\currentstep   {#2}%
   \edef\currentsubstep{#3}%
   \ifcase#4\relax
      \setupreferencing[prefix=#2:#3]
      \getbuffer[#1]%
      \par
   \else
      \setupreferencing[prefix=]
      \getbuffer[#1]%
      \page
   \fi}

\let\normalstartstep\startstep

\newcount\wantedsubstep

\unexpanded\def\startsteps
  {\ctxlua{moduledata.steps.startsteps("\thedefinedbuffer{step}")}}

\unexpanded\def\stopsteps
  {\ctxlua{moduledata.steps.stopsteps()}}

\unexpanded\def\startstep
  {\dosingleempty\startstepindeed}

\def\startstepindeed[#1]%
  {\ctxlua{moduledata.steps.startstep("#1")}%
   \normalstartstep}

\unexpanded\def\stopstep
  {\ctxlua{moduledata.steps.stopstep()}}

\let\stopsubstep\relax

\unexpanded\def\startsubstep#1\stopsubstep
  {\ctxlua{moduledata.steps.startsubstep()}%
   \ifcase\currentsubstep\relax
     #1%
   \else
     \global\advance\wantedsubstep\plusone
     \ifnum\currentsubstep>\wantedsubstep\else
       #1%
     \fi
   \fi
   \ctxlua{moduledata.steps.stopsubstep()}}

\stopmodule

\continueifinputfile{s-present-steps.mkiv}

\usemodule[present-common]

\inputpresentationfile{examples/present-steps-001.tex}