--
-- This is file `babel-bidi-basic-r.lua',
-- generated with the docstrip utility.
--
-- The original source files were:
--
-- babel.dtx  (with options: `basic-r')
-- 
--
-- Copyright (C) 2012-2021 Javier Bezos and Johannes L. Braams.
-- Copyright (C) 1989-2012 Johannes L. Braams and
--           any individual authors listed elsewhere in this file.
-- All rights reserved.
--
-- This file is part of the Babel system.
-- --------------------------------------
--
-- It may be distributed and/or modified under the
-- conditions of the LaTeX Project Public License, either version 1.3
-- 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 2003/12/01 or later.
--
-- This work has the LPPL maintenance status "maintained".
--
-- The Current Maintainer of this work is Javier Bezos.
--
-- The list of derived (unpacked) files belonging to the distribution
-- and covered by LPPL is defined by the unpacking scripts (with
-- extension |.ins|) which are part of the distribution.
--

Babel = Babel or {}

Babel.bidi_enabled = true

require('babel-data-bidi.lua')

local characters = Babel.characters
local ranges = Babel.ranges

local DIR = node.id("dir")

local function dir_mark(head, from, to, outer)
  dir = (outer == 'r') and 'TLT' or 'TRT' -- ie, reverse
  local d = node.new(DIR)
  d.dir = '+' .. dir
  node.insert_before(head, from, d)
  d = node.new(DIR)
  d.dir = '-' .. dir
  node.insert_after(head, to, d)
end

function Babel.bidi(head, ispar)
  local first_n, last_n            -- first and last char with nums
  local last_es                    -- an auxiliary 'last' used with nums
  local first_d, last_d            -- first and last char in L/R block
  local dir, dir_real
  local strong = ('TRT' == tex.pardir) and 'r' or 'l'
  local strong_lr = (strong == 'l') and 'l' or 'r'
  local outer = strong

  local new_dir = false
  local first_dir = false
  local inmath = false

  local last_lr

  local type_n = ''

  for item in node.traverse(head) do

    -- three cases: glyph, dir, otherwise
    if item.id == node.id'glyph'
      or (item.id == 7 and item.subtype == 2) then

      local itemchar
      if item.id == 7 and item.subtype == 2 then
        itemchar = item.replace.char
      else
        itemchar = item.char
      end
      local chardata = characters[itemchar]
      dir = chardata and chardata.d or nil
      if not dir then
        for nn, et in ipairs(ranges) do
          if itemchar < et[1] then
            break
          elseif itemchar <= et[2] then
            dir = et[3]
            break
          end
        end
      end
      dir = dir or 'l'
      if inmath then dir = ('TRT' == tex.mathdir) and 'r' or 'l' end
      if new_dir then
        attr_dir = 0
        for at in node.traverse(item.attr) do
          if at.number == luatexbase.registernumber'bbl@attr@dir' then
            attr_dir = at.value % 3
          end
        end
        if attr_dir == 1 then
          strong = 'r'
        elseif attr_dir == 2 then
          strong = 'al'
        else
          strong = 'l'
        end
        strong_lr = (strong == 'l') and 'l' or 'r'
        outer = strong_lr
        new_dir = false
      end

      if dir == 'nsm' then dir = strong end             -- W1
      dir_real = dir               -- We need dir_real to set strong below
      if dir == 'al' then dir = 'r' end -- W3
      if strong == 'al' then
        if dir == 'en' then dir = 'an' end                -- W2
        if dir == 'et' or dir == 'es' then dir = 'on' end -- W6
        strong_lr = 'r'                                   -- W3
      end
    elseif item.id == node.id'dir' and not inmath then
      new_dir = true
      dir = nil
    elseif item.id == node.id'math' then
      inmath = (item.subtype == 0)
    else
      dir = nil          -- Not a char
    end
    if dir == 'en' or dir == 'an' or dir == 'et' then
      if dir ~= 'et' then
        type_n = dir
      end
      first_n = first_n or item
      last_n = last_es or item
      last_es = nil
    elseif dir == 'es' and last_n then -- W3+W6
      last_es = item
    elseif dir == 'cs' then            -- it's right - do nothing
    elseif first_n then -- & if dir = any but en, et, an, es, cs, inc nil
      if strong_lr == 'r' and type_n ~= '' then
        dir_mark(head, first_n, last_n, 'r')
      elseif strong_lr == 'l' and first_d and type_n == 'an' then
        dir_mark(head, first_n, last_n, 'r')
        dir_mark(head, first_d, last_d, outer)
        first_d, last_d = nil, nil
      elseif strong_lr == 'l' and type_n ~= '' then
        last_d = last_n
      end
      type_n = ''
      first_n, last_n = nil, nil
    end
    if dir == 'l' or dir == 'r' then
      if dir ~= outer then
        first_d = first_d or item
        last_d = item
      elseif first_d and dir ~= strong_lr then
        dir_mark(head, first_d, last_d, outer)
        first_d, last_d = nil, nil
     end
    end
    if dir and not last_lr and dir ~= 'l' and outer == 'r' then
      item.char = characters[item.char] and
                  characters[item.char].m or item.char
    elseif (dir or new_dir) and last_lr ~= item then
      local mir = outer .. strong_lr .. (dir or outer)
      if mir == 'rrr' or mir == 'lrr' or mir == 'rrl' or mir == 'rlr' then
        for ch in node.traverse(node.next(last_lr)) do
          if ch == item then break end
          if ch.id == node.id'glyph' and characters[ch.char] then
            ch.char = characters[ch.char].m or ch.char
          end
        end
      end
    end
    if dir == 'l' or dir == 'r' then
      last_lr = item
      strong = dir_real            -- Don't search back - best save now
      strong_lr = (strong == 'l') and 'l' or 'r'
    elseif new_dir then
      last_lr = nil
    end
  end
  if last_lr and outer == 'r' then
    for ch in node.traverse_id(node.id'glyph', node.next(last_lr)) do
      if characters[ch.char] then
        ch.char = characters[ch.char].m or ch.char
      end
    end
  end
  if first_n then
    dir_mark(head, first_n, last_n, outer)
  end
  if first_d then
    dir_mark(head, first_d, last_d, outer)
  end
  return node.prev(head) or head
end
