if(NOT DEFINED OUTPUT_FILE OR OUTPUT_FILE STREQUAL "")
  message(FATAL_ERROR "OUTPUT_FILE is required")
endif()

if(NOT DEFINED XML_ROOT OR XML_ROOT STREQUAL "")
  message(FATAL_ERROR "XML_ROOT is required")
endif()

if(NOT DEFINED BASE_HEADER)
  set(BASE_HEADER "")
endif()

if(NOT EXISTS "${XML_ROOT}")
  message(FATAL_ERROR "XML_ROOT does not exist: ${XML_ROOT}")
endif()

set(_defined_names "")
set(_entries "")
set(_max_id -1)

if(BASE_HEADER AND EXISTS "${BASE_HEADER}")
  file(STRINGS "${BASE_HEADER}" _base_lines REGEX "^#[ \t]*define[ \t]+IDS_[A-Za-z0-9_]+[ \t]+[0-9]+([ \t].*)?$")
  foreach(_line IN LISTS _base_lines)
    string(REGEX REPLACE "^#[ \t]*define[ \t]+(IDS_[A-Za-z0-9_]+)[ \t]+([0-9]+).*$" "\\1;\\2" _parts "${_line}")
    list(LENGTH _parts _part_count)
    if(_part_count LESS 2)
      continue()
    endif()

    list(GET _parts 0 _name)
    list(GET _parts 1 _value)

    list(FIND _defined_names "${_name}" _name_index)
    if(NOT _name_index EQUAL -1)
      continue()
    endif()

    list(APPEND _defined_names "${_name}")
    set(_padded_value "000000000${_value}")
    string(REGEX REPLACE "^.*([0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9])$" "\\1" _padded_value "${_padded_value}")
    list(APPEND _entries "${_padded_value}|${_value}|${_name}")

    if(_value GREATER _max_id)
      set(_max_id "${_value}")
    endif()
  endforeach()
endif()

file(GLOB_RECURSE _xml_files "${XML_ROOT}/*.xml")
set(_discovered_names "")
foreach(_xml_file IN LISTS _xml_files)
  file(STRINGS "${_xml_file}" _xml_lines REGEX "name=\"IDS_[A-Za-z0-9_]+\"")
  foreach(_xml_line IN LISTS _xml_lines)
    string(REGEX MATCH "name=\"(IDS_[A-Za-z0-9_]+)\"" _match "${_xml_line}")
    if(_match STREQUAL "")
      continue()
    endif()

    set(_name "${CMAKE_MATCH_1}")
    list(FIND _defined_names "${_name}" _name_index)
    if(NOT _name_index EQUAL -1)
      continue()
    endif()

    list(FIND _discovered_names "${_name}" _discovered_index)
    if(NOT _discovered_index EQUAL -1)
      continue()
    endif()

    list(APPEND _discovered_names "${_name}")
  endforeach()
endforeach()

list(SORT _discovered_names)

set(_next_id "${_max_id}")
foreach(_name IN LISTS _discovered_names)
  math(EXPR _next_id "${_next_id} + 1")
  set(_padded_value "000000000${_next_id}")
  string(REGEX REPLACE "^.*([0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9])$" "\\1" _padded_value "${_padded_value}")
  list(APPEND _entries "${_padded_value}|${_next_id}|${_name}")
  list(APPEND _defined_names "${_name}")
endforeach()

list(SORT _entries)
list(LENGTH _entries _entry_count)

get_filename_component(_output_dir "${OUTPUT_FILE}" DIRECTORY)
if(NOT _output_dir STREQUAL "")
  file(MAKE_DIRECTORY "${_output_dir}")
endif()

file(WRITE "${OUTPUT_FILE}" "#pragma once\n")
file(APPEND "${OUTPUT_FILE}" "// Auto-generated from localization XML. Do not edit manually.\n")
file(APPEND "${OUTPUT_FILE}" "// Source root: ${XML_ROOT}\n")
file(APPEND "${OUTPUT_FILE}" "// Total strings: ${_entry_count}\n\n")

foreach(_entry IN LISTS _entries)
  string(REGEX REPLACE "^[0-9]+\\|([0-9]+)\\|(IDS_[A-Za-z0-9_]+)$" "\\1;\\2" _entry_parts "${_entry}")
  list(GET _entry_parts 0 _value)
  list(GET _entry_parts 1 _name)
  file(APPEND "${OUTPUT_FILE}" "#define ${_name} ${_value}\n")
endforeach()