configure

#!/bin/sh

# configure -- AutoSpectralRcpp
#
# Detects Homebrew libomp on macOS and writes src/Makevars from src/Makevars.in.
# On Linux, OpenMP is handled natively by GCC and no detection is needed.
# On Windows, configure is not run -- src/Makevars.win is used directly.
#
# This script never installs software. If libomp is absent on macOS, the
# package builds without OpenMP (single-threaded C++ only). To enable OpenMP:
#   brew install libomp

OPENMP_CPPFLAGS=""
OPENMP_LIBS=""
FLIBS_LINE=""

if [ "$(uname)" = "Darwin" ]; then
  for HOMEBREW_PREFIX in /opt/homebrew /usr/local; do
    LIBOMP_DIR="${HOMEBREW_PREFIX}/opt/libomp"
    if [ -d "${LIBOMP_DIR}" ]; then
      OPENMP_CPPFLAGS="-Xpreprocessor -fopenmp -I${LIBOMP_DIR}/include"
      OPENMP_LIBS="-L${LIBOMP_DIR}/lib -lomp"
      echo "configure: found libomp at ${LIBOMP_DIR}, enabling OpenMP"
      break
    fi
  done
  if [ -z "${OPENMP_LIBS}" ]; then
    if [ -t 1 ]; then
      echo "configure: libomp not found -- building without OpenMP (single-threaded C++ only)"
      echo "configure: to enable OpenMP, run: brew install libomp"
      echo "configure: then reinstall the package"
    else
      echo "configure: libomp not found and session is non-interactive -- cannot auto-install"
      echo "configure: to enable OpenMP, open a terminal and run: brew install libomp"
      echo "configure: then reinstall the package"
      echo "configure: building without OpenMP (single-threaded C++ only) for now"
    fi
    echo "configure: note -- keep n_threads conservative to avoid conflict with Accelerate BLAS"
  fi
else
  # Linux: gfortran is expected to be present; include $(FLIBS) as normal
  # OpenMP is handled natively by GCC via $(SHLIB_OPENMP_CXXFLAGS)
  FLIBS_LINE='$(FLIBS)'
fi

sed \
  -e "s|@OPENMP_CPPFLAGS@|${OPENMP_CPPFLAGS}|g" \
  -e "s|@OPENMP_LIBS@|${OPENMP_LIBS}|g" \
  -e "s|@FLIBS_LINE@|${FLIBS_LINE}|g" \
  src/Makevars.in > src/Makevars

exit 0