# Search TBB library (4.1 - 4.4, 2017)
#
# Own TBB (3rdparty/tbb):
# - set cmake option BUILD_TBB to ON
#
# External TBB (from system):
# - Fedora: install 'tbb-devel' package
# - Ubuntu: install 'libtbb-dev' package
#
# External TBB (from official site):
# - Linux/OSX:
#   - in tbbvars.sh replace 'SUBSTITUTE_INSTALL_DIR_HERE' with absolute path to TBB dir
#   - in terminal run 'source tbbvars.sh intel64 linux' ('source tbbvars.sh' in OSX)
# - Windows:
#   - in terminal run 'tbbvars.bat intel64 vs2015'
#
# Return:
#   - HAVE_TBB set to TRUE
#   - "tbb" target exists and added to OPENCV_LINKER_LIBS

function(ocv_tbb_verify)
  if (NOT "$ENV{TBBROOT}" STREQUAL "")
    # check that library and include dir are inside TBBROOT location
    get_filename_component(_root "$ENV{TBBROOT}" ABSOLUTE)
    get_filename_component(_lib "${TBB_ENV_LIB}" ABSOLUTE)
    get_filename_component(_inc "${TBB_ENV_INCLUDE}" ABSOLUTE)
    string(FIND "${_lib}" "${_root}" _lib_pos)
    string(FIND "${_inc}" "${_root}" _inc_pos)
    if (NOT (_lib_pos EQUAL 0 AND _inc_pos EQUAL 0))
      message(SEND_ERROR
        "Possible issue with TBB detection - TBBROOT is set, "
        "but library/include path is not inside it:\n "
        "TBBROOT: $ENV{TBBROOT}\n "
        "(absolute): ${_root}\n "
        "INCLUDE: ${_inc}\n "
        "LIBRARY: ${_lib}\n")
    endif()
  endif()
endfunction()

function(ocv_tbb_env_guess _found)
  find_path(TBB_ENV_INCLUDE NAMES "tbb/tbb.h" PATHS ENV CPATH NO_DEFAULT_PATH)
  find_path(TBB_ENV_INCLUDE NAMES "tbb/tbb.h")
  find_library(TBB_ENV_LIB NAMES "tbb" PATHS ENV LIBRARY_PATH NO_DEFAULT_PATH)
  find_library(TBB_ENV_LIB NAMES "tbb")
  find_library(TBB_ENV_LIB_DEBUG NAMES "tbb_debug" PATHS ENV LIBRARY_PATH NO_DEFAULT_PATH)
  find_library(TBB_ENV_LIB_DEBUG NAMES "tbb_debug")
  if (TBB_ENV_INCLUDE AND (TBB_ENV_LIB OR TBB_ENV_LIB_DEBUG))
    ocv_tbb_verify()
    ocv_tbb_read_version("${TBB_ENV_INCLUDE}")
    add_library(tbb UNKNOWN IMPORTED)
    set_target_properties(tbb PROPERTIES
      IMPORTED_LOCATION "${TBB_ENV_LIB}"
      IMPORTED_LOCATION_DEBUG "${TBB_ENV_LIB_DEBUG}"
      INTERFACE_INCLUDE_DIRECTORIES "${TBB_ENV_INCLUDE}"
    )
    message(STATUS "Found TBB: ${TBB_ENV_LIB}")
    set(${_found} TRUE PARENT_SCOPE)
  endif()
endfunction()

function(ocv_tbb_read_version _path)
  find_file(TBB_VER_FILE tbb/tbb_stddef.h "${_path}" NO_DEFAULT_PATH CMAKE_FIND_ROOT_PATH_BOTH)
  ocv_parse_header("${TBB_VER_FILE}" TBB_VERSION_LINES TBB_VERSION_MAJOR TBB_VERSION_MINOR TBB_INTERFACE_VERSION CACHE)
endfunction()

#=====================================================================

if(BUILD_TBB)
  add_subdirectory("${OpenCV_SOURCE_DIR}/3rdparty/tbb")
  if(NOT TARGET tbb)
    return()
  endif()
  set(HAVE_TBB TRUE)
endif()

if(NOT HAVE_TBB)
  ocv_tbb_env_guess(HAVE_TBB)
endif()

if(TBB_INTERFACE_VERSION LESS 6000) # drop support of versions < 4.0
  set(HAVE_TBB FALSE)
endif()

if(HAVE_TBB)
  list(APPEND OPENCV_LINKER_LIBS tbb)
endif()