#!/usr/bin/env texlua

-- $Id: $

-- Copyright (C) 2021 Reinhard Kotucha <reinhard.kotucha@web.de>
-- 
-- You may freely use, modify, and/or distribute this file.


local texmf_cnf_content = [[

TEXMFDIPLO = $TEXMFROOT/../texmf-diplo

% You can define additional TEXMF trees as above and add them
% to TEXMFEXTRA.  TEXMFEXTRA is a comma-separated list.  Example:
%
% TEXMFEXTRA = {$TEXMFDIPLO,$TEXMFWHATEVER}

TEXMFEXTRA = {$TEXMFDIPLO}

TEXMF = {$TEXMFCONFIG,$TEXMFVAR,$TEXMFHOME,!!$TEXMFSYSCONFIG,!!$TEXMFSYSVAR,!!$TEXMFMAIN,$TEXMFEXTRA,!!$TEXMFLOCAL,!!$TEXMFDIST}

%EOF
]]

kpse.set_program_name('texlua')

local texmfcnf = false -- value changed at initialization

local function die (str) -- Exit with error message
  io.stderr:write(str..'\n')
  os.exit(1)
end


local function cmdsubst (cmd, what) -- Unix command substitution
  local fh = io.popen(cmd, 'r')
  local ret = fh:read(what)
  fh:close()
  return ret
end


local function user_group () -- determine user and on Unix
  local user  = cmdsubst('id -un 2>/dev/null', '*l') or '<user>'
  local group = cmdsubst('id -gn 2>/dev/null', '*l') or '<group>'
  return user..':'..group
end


local function errmsg (str)
  io.stderr:write(str)
end


local function initialize () -- determine correct config file
  print('Detected System Type: '..os.type)
  print('Detected System Name: '..os.name)
  local TEXMFROOT = kpse.var_value('TEXMFROOT') or false

  if TEXMFROOT then
    print('Detected TeX Live installation at '..TEXMFROOT)
  else
    die("Can't determine root of TeX Live.")
  end

  -- set global variable texmfcnf
  texmfcnf = TEXMFROOT..'/texmf.cnf'
  
  if lfs.isfile(texmfcnf) then
    print('Found config file '..texmfcnf..'\n')
  else
    errmsg('File '..texmfcnf..' not found,\n')
    os.exit(1)
  end
end


local function msg_file_not_writable () -- abort if file is not writable
  errmsg('ERROR: The file '..texmfcnf..' is not writable.\n\n')
  if os.type == 'unix' then
    errmsg('The most likely reason is that you installed TeX Live as root.\n')

    if texmfcnf:match('^/usr/local/texlive') then
      errmsg('You can either install this program with sudo\n\n' ..
             '  sudo texlua install-diplo-config\n\n' ..
             'or steal the whole /usr/local/texlive tree.\n\n')
      errmsg('  sudo chown -R '..user_group()..' /usr/local/texlive\n')
      errmsg('\nThe latter solution is preferred for security reasons.\n')
    end
  else --windows
    errmsg('The most likely reason is that you installed TeX Live ' ..
           'with admin privileges.\nIf this is true you have to ' ..
           'invoke this program with admin privileges too.\n')
  end
  os.exit(1)
end


local function add_contents_to_texmfcnf () -- add support for texmf-diplo
  local conf = io.open(texmfcnf, 'ab') or msg_file_not_writable()
  conf:write(texmf_cnf_content)
  conf:close()
end


local function texmf_cnf_is_modified () -- is file already modified
  local conf = assert(io.open(texmfcnf, 'r'))
  for line in conf:lines() do
    if not (line:match('^%%') or line:match('^%s*$')) then
      return true
    end
  end
  conf:close()
end


local function content_installed () -- do not add content twice
  local fh=io.open(texmfcnf, 'rb')
  local content = fh:read('*a')
  fh:close()
  if content:match('TEXMFDIPLO') then
    return true
  end
end


initialize()

if content_installed() then
  errmsg('Changes were already applied.  Nothing to do.  Good bye!\n')
elseif texmf_cnf_is_modified () then
  errmsg("\nFile '".. texmfcnf .."' was modified.  I don't touch it.\n")
  errmsg('If you modified the file manually then comment out ' ..
         'your modifications, run this program again, and merge ' ..
         'your modifications later.')
  os.exit(1)
else
  add_contents_to_texmfcnf ()
  io.write('Adding texmf-diplo to '..texmfcnf..' ... ')
  io.write('[done]\n')
end


-- Local Variables:
--  mode: Lua
--  lua-indent-level: 2
--  indent-tabs-mode: nil
--  coding: utf-8-unix
-- End:
-- vim:set tabstop=2 expandtab: