% \iffalse meta-comment
%
%% Copyright (C) 2022 by Marcel Krueger
%%
%% This file may be distributed and/or modified under the
%% conditions of the LaTeX Project Public License, either
%% version 1.3c of this license or (at your option) any later
%% version. The latest version of this license is in:
%%
%% http://www.latex-project.org/lppl.txt
%%
%% and version 1.3 or later is part of all distributions of
%% LaTeX version 2005/12/01 or later.
%
%<*batch>
%<*gobble>
\ifx\jobname\relax\let\documentclass\undefined\fi
\ifx\documentclass\undefined
\csname fi\endcsname
%</gobble>
\input docstrip.tex
\keepsilent
\let\MetaPrefix\relax
\preamble
\endpreamble
\postamble
\endpostamble
\def\MetaPrefix{--}
\generate{%
  \file{lua-links.lua}{\from{lua-links.dtx}{luacode}}%
}
\let\MetaPrefix\DoubleperCent
\generate{\file{lua-links.sty}{\from{lua-links.dtx}{package}}}
\endbatchfile
%</batch>
%<*gobble>
\fi
\expandafter\ifx\csname @currname\endcsname\empty
\csname fi\endcsname
%</gobble>
%<*driver>
\documentclass{article}
\usepackage{lua-links}
\usepackage{csquotes,doc,framed,hologo,hyperref,luacolor}
\RecordChanges
\begin{document}
\DocInput{lua-links.dtx}
\PrintIndex
\PrintChanges
\end{document}
%</driver>
%<*gobble>
\fi
\RequirePackage{docstrip-luacode}
%</gobble>
% \fi
%
%
% \GetFileInfo{lua-links.sty}
% \title{The lua-links package\thanks{This document
%        corresponds to lua-links~\fileversion, dated~\filedate.}}
% \author{Marcel Kr\"uger \\ \href{mailto:tex@2krueger.de}{tex@2krueger.de}}
%
% \maketitle
% \section{Usage}
% If only I knew.
% This should be added at some point I guess.
% 
% \StopEventually{}
% \section{The implementation}
% \changes{0.1}{2022-05-18}{Initial release}
% \subsection{Lua module}
% First define the Lua module:
% \iffalse
%<*gobble>
\begin{docstrip-luacode}{lua-links}
%</gobble>
%<*luacode>
% \fi
%    \begin{macrocode}
local hlist_t = node.id'hlist'
local vlist_t = node.id'vlist'
local kern_t = node.id'kern'
local glue_t = node.id'glue'
local dir_t = node.id'dir'
local math_t = node.id'math'
local penalty_t = node.id'penalty'
local whatsit_t = node.id'whatsit'
local local_par_t = node.id'local_par'
local start_link_t = node.subtype'pdf_start_link'
local end_link_t = node.subtype'pdf_end_link'

local delayed_ids = {
  [dir_t] = true,
  [math_t] = true,
  [glue_t] = true,
  [kern_t] = true,
  [penalty_t] = true,

  [local_par_t] = true,
}

local properties = node.direct.get_properties_table()

local has_attribute = node.direct.has_attribute
local set_attribute = node.direct.set_attribute
local rangedimensions = node.direct.rangedimensions
local flush_node = node.direct.flush_node
local getattr = node.direct.getattributelist
local getboth = node.direct.getboth
local getfield = node.direct.getfield
local getglue = node.direct.getglue
local getleader = node.direct.getleader
local getlist = node.direct.getlist
local setlist = node.direct.setlist
local setheight = node.direct.setheight
local setdepth = node.direct.setdepth
local getheight = node.direct.getheight
local getdepth = node.direct.getdepth
local getnext = node.direct.getnext
local getshift = node.direct.getshift
local getid = node.direct.getid
local getsubtype = node.direct.getsubtype
local insert_after = node.direct.insert_after
local insert_before = node.direct.insert_before
local nodecopy = node.direct.copy
local nodenew = node.direct.new
local setboth = node.direct.setboth
local setlink = node.direct.setlink
local hpack = node.direct.hpack
local setfield = node.direct.setfield
local slide = node.direct.slide
local setattr = node.direct.setattributelist
local setglue = node.direct.setglue
local setnext = node.direct.setnext
local setshift = node.direct.setshift
local todirect = node.direct.todirect
local tonode = node.direct.tonode
local traverse = node.direct.traverse
local traverse_id = node.direct.traverse_id
local traverse_list = node.direct.traverse_list

local tokennew = token.new
local set_lua = token.set_lua
local scan_keyword = token.scan_keyword
local scan_list = token.scan_list
local scan_int = token.scan_int
local scan_toks = token.scan_toks
local put_next = token.put_next
local texerror = tex.error

local functions = lua.get_functions_table()
local char_given = token.command_id'char_given'

local attr = luatexbase.new_attribute'lua-links'
local mode_int = token.create'LuaLinksMode'.index
local links = {}

local vmode do
  for k, v in pairs(tex.getmodevalues()) do
  if v == "vertical" then
      vmode = k
      break
    end
  end
end
local texnest = tex.nest

%    \end{macrocode}
% This is stealing code from |lua-ul|.
% Yes, that's also why the macro is still prefixed with |luaul|.
%    \begin{macrocode}
local scan_raw_hlist do
  local create = token.create
  local lbrace, rbrace = token.new(0x7B, 1), token.new(0x7D, 2)
  tex.enableprimitives('luaul@', {'everyhbox'})
  local set_everyhbox do
    local set_toks1, set_toks2 = {create'immediateassignment',
                                  create'luaul@everyhbox', lbrace},
                                 {rbrace, create'relax'}
    function set_everyhbox(t)
      token.put_next(set_toks2)
      token.put_next(t)
      token.put_next(set_toks1)
      token.scan_token()
    end
  end
  local func = luatexbase.new_luafunction"luaul.restore_everyhbox"
  local everyhbox_saved
  functions[func] = function() set_everyhbox(everyhbox_saved) end
  local toks = {rbrace, -- Housekeeping, only for balance reasons
                lbrace, create'the', create'luaul@everyhbox', rbrace,
                create'hpack', lbrace,
                  token.new(func, token.command_id'lua_call')}
  function scan_raw_hlist()
    assert(token.get_next().command == 1)
    put_next(toks)
    token.get_next() -- Scan a corresponding brace to keep TeX's brace tracking happy
    local saved_toks = scan_toks(false, true)
    everyhbox_saved = saved_toks
    set_everyhbox{}
    local list = scan_list()
    set_everyhbox(saved_toks)
    return list
  end
end

local function start_link()
  local b = todirect(scan_raw_hlist())
  local link = getlist(b)
  if getid(link) ~= whatsit_t or getsubtype(link) ~= start_link_t then
    texerror("Link required", {"A link command is required but the \z
      link doesn't look like a link"})
  else
    local after = getnext(link)
    if after then
      texerror("Link required", {"Something unexpected followed the link. \z
        It will be ignored for now."})
      setnext(lead, nil)
    end
    table.insert(links, link)
    setlist(b, after)
    flush_node(b)
  end
  tex.attribute[attr] = #links
end
%    \end{macrocode}
%
%    \begin{macrocode}
local function stop_link()
% local reset_all = scan_keyword'*'
  tex.attribute[attr] = -0x7FFFFFFF
end

local start_link_func =
    luatexbase.new_luafunction"LuaLinkStart"
local stop_link_func =
    luatexbase.new_luafunction"LuaLinkStop"
set_lua("LuaLinkStart", start_link_func, "protected")
set_lua("LuaLinkStop", stop_link_func, "protected")
functions[start_link_func] = start_link
functions[stop_link_func] = stop_link

%    \end{macrocode}
% Add a link over some content
%    \begin{macrocode}
local add_link_hlist
local function add_link_vlist(head, outer_value, box, mode)
  local iter, state, n = traverse_list(head) -- FIXME: unset nodes
  for n, t, sub, list in traverse_list(head) do
    local processed = (t == hlist_t and add_link_hlist or add_link_vlist)(list, outer_value, n, mode)
    if processed ~= list then
      setlist(n, processed)
    end
  end
  return head
end
function add_link_hlist(head, outer_value, box, mode)
% slide(head)
  local last_value = outer_value
  local first, delayed
  local dimen_mode = mode & 6
  local unpack_mode = mode & 8 == 8

  for n, id, subtype in traverse(head) do
    if mode & 1 == 1 and delayed_ids[id] then
      delayed = delayed or n
    else
      local new_value = (not unpack_mode or id ~= hlist_t and id ~= vlist_t) and has_attribute(n, attr)
      if new_value ~= last_value then
        if last_value then
          local start_link = nodecopy(links[last_value])
          if dimen_mode ~= 0 then
            local w, h, d = rangedimensions(box, first, delayed or n)
            if dimen_mode & 2 == 2 then
              setfield(start_link, 'width', w)
            end
            if dimen_mode & 4 == 4 then
              setfield(start_link, 'height', h)
              setfield(start_link, 'depth', d)
            end
          end
          head = insert_before(head, first, start_link)
          local end_link = nodenew(whatsit_t, end_link_t)
          head = insert_before(head, delayed or n, end_link)
        end
        if new_value then
          first = n
        end
        last_value = new_value
      end
      if not last_value then
        local list = getlist(n)
        if list then
          local processed = (id == hlist_t and add_link_hlist or add_link_vlist)(list, last_value, n, mode)
          if processed ~= list then
            setlist(n, processed)
          end
        end
      end
      delayed = nil
    end
  end
  if last_value then
    local start_link = nodecopy(links[last_value])
    if dimen_mode ~= 0 then
      local w, h, d
      if delayed then
        w, h, d = rangedimensions(box, first, delayed)
      else
        w, h, d = rangedimensions(box, first)
      end
      if dimen_mode & 2 == 2 then
        setfield(start_link, 'width', w)
      end
      if dimen_mode & 4 == 4 then
        setfield(start_link, 'height', h)
        setfield(start_link, 'depth', d)
      end
    end
    head = insert_before(head, first, start_link)
    local end_link = nodenew(whatsit_t, end_link_t)
    if delayed then
      head = insert_before(head, delayed, end_link)
    else
      head = insert_after(head, nil, end_link)
    end
  end
  return head
end
luatexbase.add_to_callback('pre_shipout_filter', function(n)
  local mode = tex.count[mode_int]
  n = todirect(n)
  local list = getlist(n)
  local processed = (id == hlist_t and add_link_hlist or add_link_vlist)(list, nil, n, mode)
  if processed ~= list then
    setlist(n, processed)
  end
  return true
end, 'lua_links')
%    \end{macrocode}
% \iffalse
%</luacode>
%<*gobble>
\end{docstrip-luacode}
%</gobble>
% \fi
% \subsection{\TeX\ support package}
% Now use this stuff from \TeX
% \iffalse
%<*package>
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage
  {lua-links}
  [2022-05-18 v0.1 Lua attribute based links]

% \fi
% Only \hologo{LuaLaTeX} is supported.
% For other engines we show an error.
%    \begin{macrocode}
\ifx\directlua\undefined
  \PackageError{lua-ul}{LuaLaTeX required}%
  {Lua-links requires LuaLaTeX.
   Maybe you forgot to switch the engine in your editor?}
\fi
%    \end{macrocode}
% Some option handling
%    \begin{macrocode}
\newcount \LuaLinksMode
\DeclareOption{discard}{\LuaLinksMode=\numexpr\LuaLinksMode+1\relax}
\DeclareOption{tightH}{\LuaLinksMode=\numexpr\LuaLinksMode+2\relax}
\DeclareOption{tightV}{\LuaLinksMode=\numexpr\LuaLinksMode+4\relax}
\DeclareOption{unbox}{\LuaLinksMode=\numexpr\LuaLinksMode+8\relax}
\ProcessOptions\relax
%    \end{macrocode}
% Now load the module.
%    \begin{macrocode}
\directlua{require'lua-links'}
%    \end{macrocode}
% Since this is \LaTeX, we will continue by patching some thing which really shouldn't be patched.
%    \begin{macrocode}
\ExplSyntaxOn
\str_if_exist:NF \c_sys_backend_str {
  \sys_load_backend:n {}
}
\cs_gset_protected:Npx \__pdf_backend_link_begin:nnnw #1#2#3 {%
  \LuaLinkStart {
    \exp_args:No \use:n {
      \__pdf_backend_link_begin:nnnw {#1}{#2}{#3}
    }
  }
}
\cs_gset_protected:Npn \__pdf_backend_link_end: {%
  \LuaLinkStop
}
\ExplSyntaxOff
%    \end{macrocode}
% \iffalse
%</package>
% \fi
% \Finale