install

#!/usr/bin/env bash

set -euo pipefail

: "${KERNEL_VERSION:=5.4}"
: "${BUSYBOX_VERSION:=1.36.1}"
: "${DOWNLOAD_DIR:=./downloads}"
: "${VERIFY_KERNEL_SIG:=1}"

usage() {
  cat <<EOF
Usage: ./install [--kernel VERSION] [--busybox VERSION] [--no-verify]

Environment variables:
  KERNEL_VERSION, BUSYBOX_VERSION, DOWNLOAD_DIR, VERIFY_KERNEL_SIG
  http_proxy / https_proxy (optional, passed through to docker build)
EOF
}

while [[ $# -gt 0 ]]; do
  case "$1" in
    --kernel)
      KERNEL_VERSION="${2:-}"; shift 2;;
    --busybox)
      BUSYBOX_VERSION="${2:-}"; shift 2;;
    --no-verify)
      VERIFY_KERNEL_SIG=0; shift;;
    -h|--help)
      usage; exit 0;;
    *)
      echo "[-] Unknown argument: $1" >&2
      usage
      exit 2;;
  esac
done

echo "[*] Preparing environment..."
mkdir -p "$DOWNLOAD_DIR"

download_file() {
  local url=$1
  local file=$2
  local target="$DOWNLOAD_DIR/$file"

  if [ -f "$target" ]; then
    echo "[*] Found $file, skipping download."
  else
    echo "[+] Downloading $file..."
    if ! curl -L -C - "$url" -o "$target" --fail; then
      echo "[-] Failed to download $file. Check network/proxy."
      exit 1
    fi
  fi
}

# --- Download file to ./downloads ---
echo "[*] Checking source files in $DOWNLOAD_DIR..."
download_file "https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-$KERNEL_VERSION.tar.xz" "linux-$KERNEL_VERSION.tar.xz"
download_file "https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-$KERNEL_VERSION.tar.sign" "linux-$KERNEL_VERSION.tar.sign"
download_file "https://busybox.net/downloads/busybox-$BUSYBOX_VERSION.tar.bz2" "busybox-$BUSYBOX_VERSION.tar.bz2"

echo "[*] Starting Docker build..."
# Use DOCKER_BUILDKIT=1
DOCKER_BUILDKIT=1 docker build \
  --build-arg KERNEL_VERSION_ARG="$KERNEL_VERSION" \
  --build-arg BUSYBOX_VERSION_ARG="$BUSYBOX_VERSION" \
  --build-arg VERIFY_KERNEL_SIG_ARG="$VERIFY_KERNEL_SIG" \
  --build-arg http_proxy="${http_proxy:-}" \
  --build-arg https_proxy="${https_proxy:-}" \
  . --output type=local,dest=. 2>&1 | tee build.log