#!/usr/bin/env bash

set -euo pipefail

KERNEL_VERSION="5.4"

BUSYBOX_VERSION="1.36.1"

DOWNLOAD_DIR="./downloads"

# proxy (off/on)

export http_proxy="http://127.0.0.1:7897"

export https_proxy="http://127.0.0.1:7897"

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 http_proxy="$http_proxy" \

--build-arg https_proxy="$https_proxy" \

. --output type=local,dest=. 2>&1 | tee build.log