#!/usr/bin/env bash
set -euo pipefail

# Build BusyBox with ARM toolchain from env.sh and optional sysroot.
#
# Usage:
#   ./build.sh [SYSROOT]
#
# Examples:
#   ./build.sh
#   ./build.sh /home/stargazer/arm-uclinuxfdpiceabi/sysroot

TOOLCHAIN_PREFIX="${TOOLCHAIN_PREFIX:-arm-uclinuxfdpiceabi}"
CC_BIN="${CC_BIN:-${TOOLCHAIN_PREFIX}-gcc}"
STRIP_BIN="${STRIP_BIN:-${TOOLCHAIN_PREFIX}-strip}"
JOBS="${JOBS:-$(nproc)}"
INSTALL_DIR_NAME="${INSTALL_DIR_NAME:-_install}"

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
BUSYBOX_DIR="${SCRIPT_DIR}/busybox"
SYSROOT_DEFAULT="/home/stargazer/arm-uclinuxfdpiceabi/sysroot"
SYSROOT="${1:-${SYSROOT:-$SYSROOT_DEFAULT}}"
ENV_FILE="${ENV_FILE:-${SCRIPT_DIR}/env.sh}"
CONFIG_TEMPLATE="${SCRIPT_DIR}/config/.config"

die() {
  echo "ERROR: $*" >&2
  exit 1
}

if [ -f "${ENV_FILE}" ]; then
  # shellcheck disable=SC1090
  . "${ENV_FILE}"
fi

if ! command -v "${CC_BIN}" >/dev/null 2>&1; then
  die "Compiler not found in PATH: ${CC_BIN}"
fi
if ! command -v "${STRIP_BIN}" >/dev/null 2>&1; then
  die "Strip tool not found in PATH: ${STRIP_BIN}"
fi
if [ ! -d "${BUSYBOX_DIR}" ]; then
  die "busybox directory not found: ${BUSYBOX_DIR}"
fi
if [ ! -d "${SYSROOT}" ]; then
  die "SYSROOT not found: ${SYSROOT}"
fi

INSTALL_DIR="${SCRIPT_DIR}/${INSTALL_DIR_NAME}"
if [ "${INSTALL_DIR}" = "/" ]; then
  die "Refusing to install into /"
fi

echo "Compiler: ${CC_BIN}"
echo "Strip: ${STRIP_BIN}"
echo "SYSROOT: ${SYSROOT}"
echo "Source dir: ${BUSYBOX_DIR}"
echo "Install dir: ${INSTALL_DIR}"
echo "Config template: ${CONFIG_TEMPLATE}"

if [ ! -f "${CONFIG_TEMPLATE}" ]; then
  die "Config template not found: ${CONFIG_TEMPLATE}"
fi

cd "${BUSYBOX_DIR}"

cp "${CONFIG_TEMPLATE}" .config

# Force BusyBox shared library build profile.
if [ -x "./scripts/config" ]; then
  ./scripts/config \
    -e BUILD_LIBBUSYBOX \
    -e FEATURE_SHARED_BUSYBOX \
    -d FEATURE_INDIVIDUAL \
    -d STATIC \
    -d PIE \
    -d FEATURE_LIBBUSYBOX_STATIC
else
  echo "WARNING: scripts/config not found; shared library profile not enforced." >&2
fi

make oldconfig
make -j"${JOBS}" \
  CROSS_COMPILE="${TOOLCHAIN_PREFIX}-" \
  CC="${CC_BIN}" \
  STRIP="${STRIP_BIN}" \
  EXTRA_CFLAGS="--sysroot=${SYSROOT}" \
  EXTRA_LDFLAGS="--sysroot=${SYSROOT}"

make CONFIG_PREFIX="${INSTALL_DIR}" install

# If FEATURE_SHARED_BUSYBOX/BUILD_LIBBUSYBOX are enabled, BusyBox also
# produces a tiny launcher in 0_lib/ that links against libbusybox.
# Install that pair instead of the monolithic ./busybox to actually save space.
if [ -f "0_lib/busybox" ]; then
  install -D -m 0755 "0_lib/busybox" "${INSTALL_DIR}/bin/busybox"
fi

# Install the exact SONAME that the launcher needs (e.g. libbusybox.so.1.31.1)
shopt -s nullglob
libbusybox_candidates=(0_lib/libbusybox.so.*)
shopt -u nullglob
for f in "${libbusybox_candidates[@]}"; do
  case "${f}" in
    *_unstripped*|*.map|*.out) continue ;;
  esac
  install -D -m 0755 "${f}" "${INSTALL_DIR}/lib/$(basename "${f}")"
  # Optional convenience symlink (not required at runtime).
  ln -sf "$(basename "${f}")" "${INSTALL_DIR}/lib/libbusybox.so" 2>/dev/null || true
done

echo "Build completed successfully."
echo "Binary: ${BUSYBOX_DIR}/busybox"
echo "Shared library: ${BUSYBOX_DIR}/libbusybox.so"
echo "Installed to: ${INSTALL_DIR}"