# add a target to generate API documentation with Doxygen
find_package(Doxygen)
option(BUILD_DOCUMENTATION "Create and install the HTML based API documentation (requires Doxygen)" ${DOXYGEN_FOUND})

if(BUILD_DOCUMENTATION)
    if(NOT DOXYGEN_FOUND)
        message(FATAL_ERROR "Doxygen is needed to build the documentation.")
    endif()

    set(doxy_main_page ${CMAKE_CURRENT_SOURCE_DIR}/../README.md)
    set(doxyfile_in ${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile.in)
    set(doxyfile ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile)

    # extract version from git
    execute_process(
      COMMAND git describe --long --match v*
      WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
      OUTPUT_VARIABLE VERSION
      OUTPUT_STRIP_TRAILING_WHITESPACE
    )

    if (NOT VERSION)
      set(VERSION "v1.0-1-gcafe")
    endif()

    configure_file(${doxyfile_in} ${doxyfile} @ONLY)

    add_custom_target(doc
        COMMAND ${DOXYGEN_EXECUTABLE} ${doxyfile}
        WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
        COMMENT "Generating API documentation with Doxygen"
        VERBATIM)

    install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/html DESTINATION share/doc OPTIONAL)
endif()