configure

#!/bin/sh

# ===========================================================================
# 1. GSL DETECTION
# ===========================================================================
echo "Checking for GSL..."

GSL_CONFIG_EXEC="gsl-config"
if ! command -v "$GSL_CONFIG_EXEC" >/dev/null 2>&1; then
    if [ -x "/opt/homebrew/bin/gsl-config" ]; then
        GSL_CONFIG_EXEC="/opt/homebrew/bin/gsl-config"
    elif [ -x "/usr/local/bin/gsl-config" ]; then
        GSL_CONFIG_EXEC="/usr/local/bin/gsl-config"
    elif [ -x "/opt/local/bin/gsl-config" ]; then
        GSL_CONFIG_EXEC="/opt/local/bin/gsl-config"
    fi
fi

if ! "$GSL_CONFIG_EXEC" --version >/dev/null 2>&1; then
    echo "ERROR: GSL is not installed or gsl-config is not found."
    exit 1
fi

GSL_CFLAGS=$("$GSL_CONFIG_EXEC" --cflags)
GSL_LIBS_RAW=$("$GSL_CONFIG_EXEC" --libs)

# Replace GSL's reference CBLAS with R's BLAS (MKL, Accelerate, OpenBLAS, etc.)
# GSL's gsl_blas_* are thin wrappers around standard CBLAS — any conforming
# BLAS implementation works. The reference -lgslcblas is unoptimized; R's BLAS
# is always tuned for the platform (MKL on Linux, Accelerate on macOS, etc.)
R_BLAS_LIBS=$(R CMD config BLAS_LIBS 2>/dev/null)
if [ -n "$R_BLAS_LIBS" ]; then
    # Drop -lgslcblas, substitute R's BLAS
    GSL_LIBS=$(echo "$GSL_LIBS_RAW" | sed 's/-lgslcblas//g')
    GSL_LIBS="$GSL_LIBS $R_BLAS_LIBS"
    echo "  Using R's BLAS instead of GSL CBLAS: $R_BLAS_LIBS"
else
    # Fallback: keep GSL's reference CBLAS
    GSL_LIBS="$GSL_LIBS_RAW"
    echo "  Warning: Could not detect R's BLAS, falling back to GSL CBLAS"
fi

# ===========================================================================
# 2. OPENMP DETECTION
# ===========================================================================
echo "Checking for OpenMP support..."

OMP_CFLAGS=""
OMP_LIBS=""
OVERRIDE_LDFLAGS=""
OS=$(uname -s)
R_CC=$(R CMD config CC 2>/dev/null)
[ -z "$R_CC" ] && R_CC="gcc"

# ---------------------------------------------------------------------------
# Debugging Function: test_openmp
# ---------------------------------------------------------------------------
test_openmp() {
    TEST_CFLAGS="$1"
    TEST_LIBS="$2"
    LABEL="$3"

    TMPDIR=$(mktemp -d 2>/dev/null || mktemp -d -t 'openmptest')
    TESTFILE="$TMPDIR/test_omp.c"
    TESTOUT="$TMPDIR/test_omp"
    ERRLOG="$TMPDIR/error.log"

    cat > "$TESTFILE" <<EOF
#include <omp.h>
#include <stdio.h>
int main() {
    #pragma omp parallel
    { }
    return 0;
}
EOF

    $R_CC $TEST_CFLAGS -o "$TESTOUT" "$TESTFILE" $TEST_LIBS > "$ERRLOG" 2>&1
    RESULT=$?

    if [ $RESULT -ne 0 ]; then
        echo "  [Debug] $LABEL check failed. Compiler output:"
        sed 's/^/    /' "$ERRLOG"
    fi

    rm -rf "$TMPDIR"
    return $RESULT
}

# ---------------------------------------------------------------------------
# Platform Logic
# ---------------------------------------------------------------------------

if [ "$OS" = "Darwin" ]; then
    # --- macOS Logic ---

    # 1. Define Candidates

    # Candidate A: Homebrew Apple Silicon
    CAND_A_CFLAGS="-Xpreprocessor -fopenmp -I/opt/homebrew/opt/libomp/include -include omp.h"
    CAND_A_LIBS="/opt/homebrew/opt/libomp/lib/libomp.dylib"
    CAND_A_LDFLAGS="-L/opt/homebrew/opt/libomp/lib"

    # Candidate B: Homebrew Intel
    CAND_B_CFLAGS="-Xpreprocessor -fopenmp -I/usr/local/opt/libomp/include -include omp.h"
    CAND_B_LIBS="/usr/local/opt/libomp/lib/libomp.dylib"
    CAND_B_LDFLAGS="-L/usr/local/opt/libomp/lib"

    # Candidate C: LLVM
    CAND_C_CFLAGS="-fopenmp -I/opt/homebrew/opt/llvm/include"
    CAND_C_LIBS="/opt/homebrew/opt/llvm/lib/libomp.dylib -Wl,-rpath,/opt/homebrew/opt/llvm/lib"
    CAND_C_LDFLAGS="-L/opt/homebrew/opt/llvm/lib"

    # 2. Run Tests

    if test_openmp "$CAND_A_CFLAGS" "$CAND_A_LIBS" "Apple Silicon"; then
        echo "  Detected OpenMP: Homebrew (Apple Silicon)"
        OMP_CFLAGS="$CAND_A_CFLAGS"
        OMP_LIBS="$CAND_A_LIBS -Wl,-rpath,/opt/homebrew/opt/libomp/lib"
        OVERRIDE_LDFLAGS="$CAND_A_LDFLAGS"

    elif test_openmp "$CAND_B_CFLAGS" "$CAND_B_LIBS" "Intel Mac"; then
        echo "  Detected OpenMP: Homebrew (Intel)"
        OMP_CFLAGS="$CAND_B_CFLAGS"
        OMP_LIBS="$CAND_B_LIBS -Wl,-rpath,/usr/local/opt/libomp/lib"
        OVERRIDE_LDFLAGS="$CAND_B_LDFLAGS"

    elif test_openmp "$CAND_C_CFLAGS" "$CAND_C_LIBS" "LLVM"; then
        echo "  Detected OpenMP: Homebrew LLVM"
        OMP_CFLAGS="$CAND_C_CFLAGS"
        OMP_LIBS="$CAND_C_LIBS"
        OVERRIDE_LDFLAGS="$CAND_C_LDFLAGS"

    else
        # Fallback
        R_DEF_CFLAGS=$(R CMD config SHLIB_OPENMP_CFLAGS 2>/dev/null)
        if [ -n "$R_DEF_CFLAGS" ]; then
             echo "  Trying R Defaults ($R_DEF_CFLAGS)..."
             R_DEF_CFLAGS="$R_DEF_CFLAGS -include omp.h"

             if test_openmp "$R_DEF_CFLAGS" "$R_DEF_CFLAGS" "R-Defaults"; then
                 echo "  Detected OpenMP: R Defaults"
                 OMP_CFLAGS="$R_DEF_CFLAGS"
                 OMP_LIBS="$R_DEF_CFLAGS"
             fi
        fi
    fi

else
    # --- Linux Logic ---
    R_OMP_CFLAGS=$(R CMD config SHLIB_OPENMP_CFLAGS 2>/dev/null)
    case "$R_OMP_CFLAGS" in *ERROR*|*error*) R_OMP_CFLAGS="";; esac

    if [ -n "$R_OMP_CFLAGS" ] && test_openmp "$R_OMP_CFLAGS" "$R_OMP_CFLAGS" "Linux R-Def"; then
        OMP_CFLAGS="$R_OMP_CFLAGS"
        OMP_LIBS="$R_OMP_CFLAGS"
    elif test_openmp "-fopenmp" "-fopenmp" "Linux GCC"; then
        OMP_CFLAGS="-fopenmp"
        OMP_LIBS="-fopenmp"
    fi
fi

# ===========================================================================
# 3. WRITE MAKEVARS
# ===========================================================================
mkdir -p src

cat > src/Makevars <<EOF
## Automatically generated by configure
PKG_CFLAGS = $OMP_CFLAGS $GSL_CFLAGS
PKG_LIBS = $OMP_LIBS $GSL_LIBS
EOF

if [ -n "$OVERRIDE_LDFLAGS" ]; then
    cat >> src/Makevars <<EOF

# Override to prioritize the correct OpenMP library path
LDFLAGS = $OVERRIDE_LDFLAGS
EOF
fi

# ===========================================================================
# 4. FINAL STATUS REPORT
# ===========================================================================
echo ""
echo "-------------------------------"
echo "  RidgeR Configuration Summary "
echo "-------------------------------"
if [ -n "$OMP_CFLAGS" ]; then
    echo "  OpenMP Status:   ENABLED"
else
    echo "  OpenMP Status:   DISABLED"
fi
echo "-------------------------------"
echo ""