set(BREATHE_FOUND AUTO CACHE STRING "Enable Breathe documentation generator")
set_property(CACHE BREATHE_FOUND PROPERTY STRINGS ON OFF AUTO)

find_package(Doxygen)
find_package(Perl)
set(Python_ADDITIONAL_VERSIONS 3.7 3.6 3.5 3.4 3.3 3.2)
find_package(PythonInterp)
if (PYTHONINTERP_FOUND)
  find_package(Sphinx)
  include(FindPythonModule)
  find_python_module(breathe)
  find_python_module(recommonmark)
  if(DOXYGEN_FOUND AND PERL_FOUND AND PYTHONINTERP_FOUND AND SPHINX_EXECUTABLE AND breathe AND recommonmark)
    set(BREATHE_FOUND ON CACHE STRING "Breathe documentation generator enabled" FORCE)
  else()
    set(BREATHE_FOUND OFF CACHE STRING "Breathe documentation generator disabled" FORCE)
  endif()
else()
  set(BREATHE_FOUND OFF CACHE STRING "Breathe documentation generator disabled" FORCE)
endif()


function(add_breathe_target)
  if(BREATHE_FOUND)
    set(options)
    set(oneValueArgs SOURCE_DIR BUILD_DIR CACHE_DIR HTML_DIR DOXY_FILE CONF_FILE TARGET_NAME COMMENT)
    set(multiValueArgs)

    cmake_parse_arguments(_BREATHE "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})

    configure_file(${_BREATHE_CONF_FILE} ${_BREATHE_BUILD_DIR}/conf.py @ONLY)
    configure_file(${_BREATHE_DOXY_FILE} ${_BREATHE_BUILD_DIR}/Doxyfile @ONLY)

    add_custom_target(${_BREATHE_TARGET_NAME} VERBATIM
      COMMAND ${SPHINX_EXECUTABLE} -q -b html -c ${_BREATHE_BUILD_DIR}
                                              -d ${_BREATHE_CACHE_DIR}
                                                 ${_BREATHE_SOURCE_DIR}
                                                 ${_BREATHE_HTML_DIR}
      COMMENT "Building ${_BREATHE_TARGET_NAME} documentation with Breathe"
      )
  else()
    add_custom_target(${_BREATHE_TARGET_NAME} VERBATIM
      COMMENT "Breathe is not found. Skipping target ${_BREATHE_TARGET_NAME} build")
  endif()
endfunction()