configure

#!/bin/sh
# OptiLCMS configure — autodetects macOS toolchain gaps so users don't need to
# hand-patch ~/.R/Makevars. Generates src/Makevars from src/Makevars.in.
#
# macOS-specific headers the package needs that aren't in the Xcode SDK:
#   - <omp.h>     (OpenMP)  — supplied by Homebrew `libomp`
#   - <libintl.h> (gettext) — supplied by Homebrew `gettext`
#
# Both are in glibc/gcc on Linux, so nothing special is needed there.
# On macOS we probe Homebrew prefixes and splice the right -I/-L flags in.

R_HOME="${R_HOME:-$(R RHOME 2>/dev/null)}"
RBIN="${R_HOME}/bin/R"
R_CXX=$("${RBIN}" CMD config CXX)
R_CC=$("${RBIN}" CMD config CC)

# Query an R config variable and return empty string if R reports it missing.
get_r_cfg() {
    out=$("${RBIN}" CMD config "$1" 2>&1 || true)
    case "${out}" in
        ERROR:*|*"no information for variable"*)
            echo ""
            ;;
        *)
            echo "${out}"
            ;;
    esac
}

SHLIB_OMP_CXX=$(get_r_cfg SHLIB_OPENMP_CXXFLAGS)
SHLIB_OMP_C=$(get_r_cfg SHLIB_OPENMP_CFLAGS)

# Older/non-standard R builds may expose OPENMP_*FLAGS instead.
if [ -z "${SHLIB_OMP_CXX}" ]; then
    SHLIB_OMP_CXX=$(get_r_cfg OPENMP_CXXFLAGS)
fi
if [ -z "${SHLIB_OMP_C}" ]; then
    SHLIB_OMP_C=$(get_r_cfg OPENMP_CFLAGS)
fi

uname_s=$(uname -s 2>/dev/null)
is_darwin=0
[ "${uname_s}" = "Darwin" ] && is_darwin=1

OPENMP_CFLAGS=""
OPENMP_CXXFLAGS=""
OPENMP_LIBS=""
EXTRA_CPPFLAGS=""
EXTRA_LIBS=""

# ---- helpers --------------------------------------------------------------

# probe_compile COMPILE_FLAGS LINK_FLAGS HEADER SYMBOL
# Compiles a minimal program that uses HEADER and SYMBOL. Returns 0 on success.
probe_compile() {
    tmp=$(mktemp -d 2>/dev/null || mktemp -d -t optilcms-conf)
    cat > "${tmp}/probe.cpp" <<EOF
#include <${3}>
int main() { (void)${4}; return 0; }
EOF
    ${R_CXX} ${1} "${tmp}/probe.cpp" -o "${tmp}/probe" ${2} >/dev/null 2>&1
    rc=$?
    rm -rf "${tmp}"
    return $rc
}

first_existing_prefix() {
    # Echoes the first directory from the arg list that contains include/${header}.
    header="${1}"; shift
    for p in "$@"; do
        if [ -n "${p}" ] && [ -f "${p}/include/${header}" ]; then
            echo "${p}"
            return 0
        fi
    done
    return 1
}

# ---- OpenMP (omp.h) -------------------------------------------------------

if [ ${is_darwin} -eq 1 ]; then
    echo "configure: macOS detected — probing OpenMP / libomp"
    if [ -n "${SHLIB_OMP_CXX}" ] && probe_compile "${SHLIB_OMP_CXX}" "${SHLIB_OMP_CXX}" omp.h "omp_get_max_threads()"; then
        OPENMP_CFLAGS="${SHLIB_OMP_C}"
        OPENMP_CXXFLAGS="${SHLIB_OMP_CXX}"
        OPENMP_LIBS="${SHLIB_OMP_CXX}"
        echo "configure: R's SHLIB_OPENMP flags work as-is"
    else
        brew_omp=$(first_existing_prefix omp.h /opt/homebrew/opt/libomp /usr/local/opt/libomp)
        if [ -n "${brew_omp}" ]; then
            cxx="-Xclang -fopenmp -I${brew_omp}/include"
            ld="-L${brew_omp}/lib -lomp"
            if probe_compile "${cxx}" "${ld}" omp.h "omp_get_max_threads()"; then
                OPENMP_CFLAGS="${cxx}"
                OPENMP_CXXFLAGS="${cxx}"
                OPENMP_LIBS="${ld}"
                echo "configure: using Homebrew libomp at ${brew_omp}"
            fi
        fi
    fi
    if [ -z "${OPENMP_CXXFLAGS}" ]; then
        echo "configure: WARNING — no OpenMP. To enable: brew install libomp"
        echo "configure:           (pense/entropy parallel paths will be serial)"
    fi
else
    OPENMP_CFLAGS="${SHLIB_OMP_C}"
    OPENMP_CXXFLAGS="${SHLIB_OMP_CXX}"
    OPENMP_LIBS="${SHLIB_OMP_CXX}"

    if [ -z "${OPENMP_CXXFLAGS}" ]; then
        # Linux toolchains typically accept plain -fopenmp even when R config
        # does not expose SHLIB_OPENMP_CXXFLAGS.
        if probe_compile "-fopenmp" "-fopenmp" omp.h "omp_get_max_threads()"; then
            OPENMP_CFLAGS="-fopenmp"
            OPENMP_CXXFLAGS="-fopenmp"
            OPENMP_LIBS="-fopenmp"
            echo "configure: ${uname_s} — SHLIB_OPENMP_CXXFLAGS missing; using fallback -fopenmp"
        else
            echo "configure: ${uname_s} — OpenMP flags unavailable; building without OpenMP"
        fi
    else
        echo "configure: ${uname_s} — using R's OpenMP flags: ${SHLIB_OMP_CXX}"
    fi
fi

# ---- gettext (libintl.h) — macOS only -------------------------------------

if [ ${is_darwin} -eq 1 ]; then
    echo "configure: probing gettext / libintl"
    if probe_compile "" "" libintl.h "gettext(\"\")" ; then
        echo "configure: libintl.h resolves without extra flags"
    else
        brew_gettext=$(first_existing_prefix libintl.h /opt/homebrew/opt/gettext /usr/local/opt/gettext)
        if [ -n "${brew_gettext}" ]; then
            cpp="-I${brew_gettext}/include"
            ld="-L${brew_gettext}/lib -lintl"
            if probe_compile "${cpp}" "${ld}" libintl.h "gettext(\"\")"; then
                EXTRA_CPPFLAGS="${EXTRA_CPPFLAGS} ${cpp}"
                EXTRA_LIBS="${EXTRA_LIBS} ${ld}"
                echo "configure: using Homebrew gettext at ${brew_gettext}"
            fi
        else
            echo "configure: WARNING — libintl.h not found. To install: brew install gettext"
        fi
    fi
fi

# ---- generate src/Makevars from src/Makevars.in ---------------------------

if [ ! -f src/Makevars.in ]; then
    echo "configure: ERROR — src/Makevars.in missing" >&2
    exit 1
fi

# Strip leading whitespace from the accumulators so substitutions stay clean.
EXTRA_CPPFLAGS=$(echo "${EXTRA_CPPFLAGS}" | sed -e 's/^ *//')
EXTRA_LIBS=$(echo "${EXTRA_LIBS}" | sed -e 's/^ *//')

sed -e "s|@OPENMP_CFLAGS@|${OPENMP_CFLAGS}|g" \
    -e "s|@OPENMP_CXXFLAGS@|${OPENMP_CXXFLAGS}|g" \
    -e "s|@OPENMP_LIBS@|${OPENMP_LIBS}|g" \
    -e "s|@EXTRA_CPPFLAGS@|${EXTRA_CPPFLAGS}|g" \
    -e "s|@EXTRA_LIBS@|${EXTRA_LIBS}|g" \
    src/Makevars.in > src/Makevars

echo "configure: wrote src/Makevars"
echo "  OPENMP_CFLAGS   = ${OPENMP_CFLAGS}"
echo "  OPENMP_CXXFLAGS = ${OPENMP_CXXFLAGS}"
echo "  OPENMP_LIBS     = ${OPENMP_LIBS}"
echo "  EXTRA_CPPFLAGS  = ${EXTRA_CPPFLAGS}"
echo "  EXTRA_LIBS      = ${EXTRA_LIBS}"
exit 0