#!/usr/bin/env bash
#
# Fetch and build upstream SHTNS, then record how to link against it.
#
#   ./bootstrap.sh              # CPU, with OpenMP; adds CUDA if nvcc is on PATH
#   ./bootstrap.sh --no-cuda    # CPU only, even if nvcc is there
#   ./bootstrap.sh --rev master # a different revision than the pinned one
#
# Writes shtns.mk, which the Makefile includes: the library name, the link
# flags configure decided on, and whether GPU transforms were compiled in.
# Re-run it after changing --rev or the CUDA choice; it is idempotent otherwise.
set -euo pipefail

cd "$(dirname "$0")"

# SHTNS 3.7.5, master as of 2026-05-07. Pinned so a change upstream shows up as
# a deliberate bump here rather than as a benchmark that quietly moved.
REV=4e69ceb3fc5f19475d55b03ff0fdec210dc3075e
URL=https://bitbucket.org/nschaeff/shtns.git
DIR=shtns
WANT_CUDA=auto
CUDA_ARCH=

while [ $# -gt 0 ]; do
  case "$1" in
    --no-cuda) WANT_CUDA=no ;;
    --cuda) WANT_CUDA=yes ;;
    --cuda=*) WANT_CUDA=yes; CUDA_ARCH="${1#*=}" ;;
    --rev) shift; REV="$1" ;;
    --rev=*) REV="${1#*=}" ;;
    -h|--help)
      sed -n '2,12p' "$0" | sed 's/^# \{0,1\}//'
      exit 0 ;;
    *) echo "bootstrap: unknown option '$1'" >&2; exit 2 ;;
  esac
  shift
done

if [ "$WANT_CUDA" = auto ]; then
  if command -v nvcc >/dev/null 2>&1; then WANT_CUDA=yes; else WANT_CUDA=no; fi
fi

# ---------------------------------------------------------------------- clone
if [ ! -d "$DIR/.git" ]; then
  echo "==> cloning $URL"
  git clone "$URL" "$DIR"
fi
echo "==> checking out $REV"
# --unshallow so an existing shallow clone can still reach a --rev other than the
# one it was cloned at; it errors on a full clone, hence the fallback.
git -C "$DIR" fetch --tags --unshallow origin 2>/dev/null || git -C "$DIR" fetch --tags origin
git -C "$DIR" checkout --detach "$REV"

# ------------------------------------------------------------------ configure
CONF=(--enable-openmp)
if [ "$WANT_CUDA" = yes ]; then
  if [ -n "$CUDA_ARCH" ]; then
    CONF+=("--enable-cuda=$CUDA_ARCH")
  else
    CONF+=(--enable-cuda)
  fi
  # configure looks for these where CUDA_PATH points; say so if it is unset and
  # nvcc is somewhere obvious, since the error it produces otherwise is opaque.
  if [ -z "${CUDA_PATH:-}" ]; then
    nvcc_dir=$(dirname "$(command -v nvcc)")
    export CUDA_PATH="${nvcc_dir%/bin}"
    echo "==> CUDA_PATH was unset; using $CUDA_PATH"
  fi
fi

echo "==> configure ${CONF[*]}"
( cd "$DIR" && ./configure "${CONF[@]}" )

echo "==> make"
( cd "$DIR" && make -j"$(getconf _NPROCESSORS_ONLN)" )

# --------------------------------------------------------------- record how to
# link. configure has already worked all of this out; read it back rather than
# guessing, so a machine that needed MKL or a different FFTW still links.
libname=$(sed -n 's/^libname *= *//p' "$DIR/Makefile" | head -1)
libs=$(sed -n 's/^LIBS=//p' "$DIR/Makefile" | head -1)
if [ ! -f "$DIR/$libname" ]; then
  echo "bootstrap: expected $DIR/$libname but it is not there" >&2
  exit 1
fi

# Whether the GPU entry points are actually in the archive — asked of the
# library rather than of configure's intentions, since --enable-cuda can succeed
# at configure time and still leave them out.
gpu=0
if nm -g "$DIR/$libname" 2>/dev/null | grep -q ' T cu_spat_to_SH_float'; then
  gpu=1
elif sed -n 's/^objs *= *//p' "$DIR/Makefile" | grep -q 'sht_gpu\.o'; then
  gpu=1 # no nm on this host; trust what configure put in the object list
fi

fft=none
[ "$gpu" = 1 ] && fft=vkfft
if [ "$gpu" = 1 ] && ! grep -q '^#define VKFFT_BACKEND' "$DIR/sht_config.h"; then
  # SHTNS falls back to cuFFT when vkfft/vkFFT.h is absent, and its configure
  # does not add -lcufft (the check is commented out), so we have to.
  fft=cufft
  libs="$libs -lcufft"
fi

cat > shtns.mk <<EOF
# Generated by bootstrap.sh — do not edit; re-run it instead.
SHTNS_DIR = $DIR
SHTNS_LIB = \$(SHTNS_DIR)/$libname
SHTNS_LDLIBS = $libs
SHTNS_HAS_GPU = $gpu
SHTNS_GPU_FFT = $fft
EOF

echo
echo "==> built $DIR/$libname (GPU transforms: $([ "$gpu" = 1 ] && echo yes || echo no))"
if [ "$gpu" = 1 ]; then
  echo "    GPU Fourier stage: $fft"
  if [ "$fft" = cufft ]; then
    echo "    NOTE: SHTNS' cuFFT path handles only the theta-contiguous layout, so"
    echo "          --layout phi will not work. vkfft/vkFFT.h is normally in the SHTNS"
    echo "          tree; if it is missing, that is why."
  fi
fi
echo "    link flags: $libs"
echo
echo "Now: make"