#!/usr/bin/env bash
# Ubuntu HWE 6.17: optional apply user patch, build-dep, binary-generic debs, optional install.
# No default patch in-repo; set PATCH=/path/to/file.patch for apply.
# Run on Ubuntu (Noble or host with linux-hwe-6.17 sources); requires sudo for apt/dpkg.
set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
REPO_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
PATCH="${PATCH:-}"
SRC="${SRC:-$REPO_ROOT/kernel-src/linux-hwe-6.17-6.17.0}"
JOBS="${CONCURRENCY_LEVEL:-$(nproc)}"

usage() {
  echo "Usage: $0 [apply|deps|build|install|all]"
  echo "  apply  - patch -p1 in SRC (requires PATCH=/abs/path/to.patch)"
  echo "  deps   - sudo apt build-dep linux-hwe-6.17 + build tools"
  echo "  build  - fakeroot debian/rules clean && binary-generic"
  echo "  install- sudo dpkg -i newest linux-image-* and linux-modules-* in parent of SRC"
  echo "  all    - deps then build (does NOT apply patches; run apply separately if needed)"
  echo "Env: PATCH=path SRC=path to linux-hwe-6.17-6.17.0 tree"
  echo "See: patches/ubuntu-hwe-6.17/README.md"
}

if [[ ! -f "$SRC/debian/rules" ]]; then
  echo "ERROR: kernel source not found at SRC=$SRC"
  exit 1
fi

cmd_apply() {
  if [[ -z "${PATCH}" ]]; then
    echo "ERROR: apply requires PATCH=/absolute/path/to/your.patch" >&2
    echo "  Example: PATCH=\"$REPO_ROOT/patches/ubuntu-hwe-6.17/0001-foo.patch\" $0 apply" >&2
    exit 1
  fi
  if [[ ! -f "$PATCH" ]]; then
    echo "ERROR: PATCH file not found: $PATCH" >&2
    exit 1
  fi
  cd "$SRC"
  patch -p1 < "$PATCH"
  echo "Applied: $PATCH"
}

cmd_deps() {
  sudo apt-get update
  sudo apt-get build-dep -y linux-hwe-6.17
  sudo apt-get install -y fakeroot build-essential libncurses-dev libssl-dev ccache \
    gawk debhelper libelf-dev libdw-dev flex bison bc python3-dev
}

cmd_build() {
  cd "$SRC"
  export CONCURRENCY_LEVEL="$JOBS"
  fakeroot debian/rules clean
  fakeroot debian/rules binary-generic
}

cmd_install() {
  parent="$(dirname "$SRC")"
  cd "$parent"
  mapfile -t imgs < <(ls -t linux-image-*.deb 2>/dev/null || true)
  mapfile -t mods < <(ls -t linux-modules-*.deb 2>/dev/null || true)
  if [[ ${#imgs[@]} -eq 0 || ${#mods[@]} -eq 0 ]]; then
    echo "No linux-image-*.deb or linux-modules-*.deb in $parent — build first."
    exit 1
  fi
  echo "Installing: ${imgs[0]} ${mods[0]}"
  sudo dpkg -i "${imgs[0]}" "${mods[0]}"
  echo "Optional: sudo dpkg -i linux-headers-*.deb linux-modules-extra-*.deb from same directory"
  echo "Then: sudo reboot"
}

case "${1:-}" in
  apply) cmd_apply ;;
  deps) cmd_deps ;;
  build) cmd_build ;;
  install) cmd_install ;;
  all)
    cmd_deps
    cmd_build
    echo "Build done. Debs should be in: $(dirname "$SRC")"
    echo "Run: $0 install   (after reviewing package names)"
    echo "If you use a custom patch: PATCH=... $0 apply   (before build, on a clean tree)"
    ;;
  *) usage; exit 1 ;;
esac