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# -------------------------------------------------------------------------------------------------
# script expects the following variables:
    # - TARGET_ADD_TOOL_DEPENDENCY_TARGET
    # - TARGET_ADD_TOOL_DEPENDENCY_TOOL
# -------------------------------------------------------------------------------------------------

# use the python binray of the dev package if available
if((NOT python_PATH OR NOT EXISTS python_PATH) AND MDL_DEPENDENCY_PYTHON_DEV_EXE)
    set(python_PATH ${MDL_DEPENDENCY_PYTHON_DEV_EXE} CACHE FILEPATH "Path of the Python 2.7+ binary." FORCE)
endif()

# use a default fallback to find python3
if(NOT python_PATH OR NOT EXISTS ${python_PATH})
    # use the cmake built-in find script (requires 3.12)
    if(EXISTS ${PYTHON_DIR})
        set(Python3_ROOT_DIR ${PYTHON_DIR})
    endif()
    find_package (Python3 COMPONENTS Interpreter)

    # use the found interpreter as the default python interpreter tool
    if(TARGET Python3::Interpreter)
        message(WARNING "Changing \"python_PATH\" to \"${Python3_EXECUTABLE}\" because specified path does not exist: \"${python_PATH}\"")
        set(python_PATH ${Python3_EXECUTABLE} CACHE FILEPATH "Path of the Python 3.8+ binary." FORCE)
    endif()
endif()

# use a default fallback to find python2
if(NOT python_PATH OR NOT EXISTS ${python_PATH})
    # use the cmake built-in find script (requires 3.12)
    if(EXISTS ${PYTHON_DIR})
        set(Python2_ROOT_DIR ${PYTHON_DIR})
    endif()
    find_package (Python2 COMPONENTS Interpreter)

    # use the found interpreter as the default python interpreter tool
    if(TARGET Python2::Interpreter)
        message(WARNING "Changing \"python_PATH\" to \"${Python2_EXECUTABLE}\" because specified path does not exist: \"${python_PATH}\"")
        set(python_PATH ${Python3_EXECUTABLE} CACHE FILEPATH "Path of the Python 2.7+ binary." FORCE)
    endif()
endif()

# fallbacks did not work
if(NOT python_PATH OR NOT EXISTS ${python_PATH})
    MESSAGE(FATAL_ERROR "The tool dependency \"${TARGET_ADD_TOOL_DEPENDENCY_TOOL}\" for target \"${TARGET_ADD_TOOL_DEPENDENCY_TARGET}\" could not be resolved. Please specify \"PYTHON_DIR\" or \"python_PATH\"" )
endif()

# call --version
get_filename_component(python_PATH_ABS ${python_PATH} REALPATH)
set(python_PATH ${python_PATH_ABS} CACHE FILEPATH "Path of the Python 2.7+ binary." FORCE)
execute_process(COMMAND "${python_PATH}" "--version" 
    OUTPUT_VARIABLE 
        _PYTHON_VERSION_STRING 
    ERROR_VARIABLE 
        _PYTHON_VERSION_STRING
    )

# check version
if("MDL_BINARY_RELEASE" IN_LIST MDL_ADDITIONAL_COMPILER_DEFINES)
    set(_MIN_VERSION "2.7.0")
else()
    set(_MIN_VERSION "3.8.0")
endif()

if(NOT _PYTHON_VERSION_STRING)
    message(STATUS "python_PATH: ${python_PATH}")
    message(FATAL_ERROR "Python version could not be determined.")
else()
    # parse version number
    STRING(REGEX MATCH "[0-9]+\\.[0-9]+\\.[0-9]+" _PYTHON_VERSION_STRING ${_PYTHON_VERSION_STRING})
    if((${_PYTHON_VERSION_STRING} VERSION_LESS ${_MIN_VERSION}))
        message(FATAL_ERROR "Python ${_MIN_VERSION} or higher is required but Python ${_PYTHON_VERSION_STRING} was found instead. Please set the CMake option 'python_PATH' that needs to point to a supported python3 interpreter.")
    endif()
endif()