add_library(MathFunctions MathFunctions.cxx)

# should we use our own math functions
option(USE_MYMATH "Use tutorial provided math implementation" ON)
if (USE_MYMATH)
  target_compile_definitions(MathFunctions PRIVATE "USE_MYMATH")

  # library that just does sqrt
  add_library(SqrtLibrary STATIC
              mysqrt.cxx
              )

  # link SqrtLibrary to tutorial_compiler_flags
  target_link_libraries(SqrtLibrary PUBLIC tutorial_compiler_flags)

  # does this system provide the log and exp functions?
  include(CheckCXXSourceCompiles)
  check_cxx_source_compiles("
    #include <cmath>
    int main() {
      std::log(1.0);
      return 0;
    }
  " HAVE_LOG)
  check_cxx_source_compiles("
    #include <cmath>
    int main() {
      std::exp(1.0);
      return 0;
    }
  " HAVE_EXP)

  # add compile definitions
  if(HAVE_LOG AND HAVE_EXP)
    target_compile_definitions(SqrtLibrary
                               PRIVATE "HAVE_LOG" "HAVE_EXP"
                               )
  endif()

  target_link_libraries(MathFunctions PRIVATE SqrtLibrary)
endif()

# state that anybody linking to us needs to include the current source dir
# to find MathFunctions.h, while we don't.
target_include_directories(MathFunctions
                           INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}
                           )

# link MathFunctions to tutorial_compiler_flags
target_link_libraries(MathFunctions PUBLIC tutorial_compiler_flags)

# install libs
set(installable_libs MathFunctions tutorial_compiler_flags)
if(TARGET SqrtLibrary)
  list(APPEND installable_libs SqrtLibrary)
endif()
install(TARGETS ${installable_libs} DESTINATION lib)
# install include headers
install(FILES MathFunctions.h DESTINATION include)