#!/usr/bin/env bash
# build-linux-rpi.sh - build/install a newer linux-rpi from rpi-6.18.y
set -euo pipefail

if [[ ${EUID:-0} -ne 0 ]]; then
  echo "run as root (sudo) to install build deps and kernel packages" >&2
  exit 1
fi

BUILD_USER=${LESAVKA_KERNEL_BUILD_USER:-${SUDO_USER:-$(id -un)}}
if [[ -z $BUILD_USER || $BUILD_USER == root ]]; then
  echo "missing non-root build user; set LESAVKA_KERNEL_BUILD_USER" >&2
  exit 1
fi

KERNEL_REPO=${LESAVKA_KERNEL_REPO:-https://github.com/raspberrypi/linux.git}
KERNEL_BRANCH=${LESAVKA_KERNEL_BRANCH:-rpi-6.18.y}
KERNEL_COMMIT=${LESAVKA_KERNEL_COMMIT:-}
PKGBUILD_REPO=${LESAVKA_KERNEL_PKG_REPO:-https://github.com/archlinuxarm/PKGBUILDs.git}
BUILD_ROOT=${LESAVKA_KERNEL_BUILD_ROOT:-/var/tmp/lesavka-linux-rpi}
PKGREL=${LESAVKA_KERNEL_PKGREL:-2}
JOBS=${LESAVKA_KERNEL_JOBS:-2}

HEARTBEAT=/etc/lesavka/watchdog.touch
if [[ -w $HEARTBEAT && -z ${LESAVKA_DISABLE_KEEPALIVE:-} ]]; then
  (while true; do touch "$HEARTBEAT"; sleep 600; done) &
  KEEPALIVE_PID=$!
  trap 'kill $KEEPALIVE_PID' EXIT
fi

if [[ -z $KERNEL_COMMIT ]]; then
  KERNEL_COMMIT=$(git ls-remote "$KERNEL_REPO" "refs/heads/$KERNEL_BRANCH" | awk '{print $1}')
fi
if [[ -z $KERNEL_COMMIT ]]; then
  echo "failed to resolve kernel commit for $KERNEL_BRANCH" >&2
  exit 1
fi

KERNEL_VERSION=$(
  curl -fsSL "https://raw.githubusercontent.com/raspberrypi/linux/$KERNEL_COMMIT/Makefile" |
    awk -F' = ' '
      /^VERSION =/ {v=$2}
      /^PATCHLEVEL =/ {p=$2}
      /^SUBLEVEL =/ {s=$2}
      END { if (v && p && s) print v "." p "." s }'
)
if [[ -z $KERNEL_VERSION ]]; then
  echo "failed to determine kernel version from $KERNEL_COMMIT" >&2
  exit 1
fi

TARGET_VERSION="${KERNEL_VERSION}-${PKGREL}"
INSTALLED_VERSION=$(pacman -Qi linux-rpi 2>/dev/null | awk -F': ' '/Version/{print $2}')
if [[ -n $INSTALLED_VERSION && $INSTALLED_VERSION == "$TARGET_VERSION"* ]]; then
  echo "linux-rpi already at $TARGET_VERSION"
  exit 0
fi

echo "==> Building linux-rpi $KERNEL_VERSION ($KERNEL_COMMIT) pkgrel=$PKGREL"

pacman -Sy --needed --noconfirm git bc kmod inetutils base-devel

rm -rf "$BUILD_ROOT"
mkdir -p "$BUILD_ROOT"
chown "$BUILD_USER":"$BUILD_USER" "$BUILD_ROOT"

sudo -u "$BUILD_USER" git clone --depth 1 "$PKGBUILD_REPO" "$BUILD_ROOT/PKGBUILDs"
cp -a "$BUILD_ROOT/PKGBUILDs/core/linux-rpi" "$BUILD_ROOT/linux-rpi"
chown -R "$BUILD_USER":"$BUILD_USER" "$BUILD_ROOT/linux-rpi"

sudo -u "$BUILD_USER" bash -c "
  set -euo pipefail
  cd '$BUILD_ROOT/linux-rpi'
  sed -i 's/^pkgver=.*/pkgver=$KERNEL_VERSION/' PKGBUILD
  sed -i 's/^pkgrel=.*/pkgrel=$PKGREL/' PKGBUILD
  sed -i 's/^_commit=.*/_commit=$KERNEL_COMMIT/' PKGBUILD
  makepkg -g > /tmp/lesavka-kernel.sums
"

sudo -u "$BUILD_USER" BUILD_ROOT="$BUILD_ROOT" python - <<'PY'
import re
from pathlib import Path
import os

root = Path(os.environ["BUILD_ROOT"])
pkgbuild = root / "linux-rpi" / "PKGBUILD"
sums = Path("/tmp/lesavka-kernel.sums").read_text().splitlines()
text = pkgbuild.read_text()
for line in sums:
    if not line.startswith("sha256sums"):
        continue
    key = line.split("=", 1)[0]
    text = re.sub(rf"^{re.escape(key)}=.*$", line, text, flags=re.M)
pkgbuild.write_text(text)
PY

sudo -u "$BUILD_USER" bash -c "
  set -euo pipefail
  cd '$BUILD_ROOT/linux-rpi'
  MAKEFLAGS='-j$JOBS' makepkg -s --noconfirm
"

mapfile -t PKGS < <(ls "$BUILD_ROOT/linux-rpi"/*.pkg.tar.* 2>/dev/null)
if [[ ${#PKGS[@]} -eq 0 ]]; then
  echo "no kernel packages built" >&2
  exit 1
fi

pacman -U --noconfirm "${PKGS[@]}"
echo "✅ linux-rpi upgraded to $TARGET_VERSION (reboot required)"