#
# Copyright (C) 2005-2017 Centre National d'Etudes Spatiales (CNES)
#
# This file is part of Orfeo Toolbox
#
#     https://www.orfeo-toolbox.org/
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
function(isfile_symlink file result_var1 result_var2)
  #
  # A file is not executable until proven otherwise:
  #
  set(${result_var1} 0 PARENT_SCOPE)
  set(${result_var2} "" PARENT_SCOPE)

  get_filename_component(file_full "${file}" ABSOLUTE)
  string(TOLOWER "${file_full}" file_full_lower)

  # If file name ends in .lnk on Windows,
  # *assume* symlink a.k.a shortcut.
  #
  if(WIN32 AND NOT UNIX)
    if("${file_full_lower}" MATCHES "\\.lnk$")
      set(${result_var1} 1 PARENT_SCOPE)
      #Assuming the file is linked to a file
      #with same name without .lnk extension
      get_filename_component(file_full_name_we "${file_full}" NAME_WE)
      set(${result_var2} "${file_full_name_we}" PARENT_SCOPE)
      return()
    endif()

    # A clause could be added here that uses output or return value of dumpbin
    # to determine ${result_var}. In 99%+? practical cases, the exe name
    # match will be sufficient...
    #
  endif()

  #if we are not on a unix or unix-like platform,
  #then we don't have any business after this line.
  if(NOT UNIX)
    return()
  endif()

  # Use the information returned from the Unix shell command "file" to
  # determine if ${file_full} should be considered an executable file...
  #
  # If the file command's output contains "executable" and does *not* contain
  # "text" then it is likely an executable suitable for prerequisite analysis
  # via the get_prerequisites macro.
  
  execute_process(COMMAND "${READLINK}" "${file_full}"
    RESULT_VARIABLE readlink_rv
    OUTPUT_VARIABLE readlink_ov
    ERROR_VARIABLE readlink_ev
    OUTPUT_STRIP_TRAILING_WHITESPACE
    )

  if(PKG_DEBUG)
    message("${READLINK} on '${file_full} has output: '${readlink_ov}'\nreadlink_ev=${readlink_ev}")
  endif()
  
  if(readlink_rv STREQUAL "1")
    set(${result_var1} 0 PARENT_SCOPE)
    set(${result_var2} "" PARENT_SCOPE)
    return()
  endif()

  #got a symlink!. set result_var1 to TRUE
  set(${result_var1} 1 PARENT_SCOPE)

  #Now get the resolved link to result_var2
  set(symlinked_to)
  string(STRIP ${readlink_ov} symlinked_to)
  set(${result_var2} "${symlinked_to}" PARENT_SCOPE)

  return()

endfunction()