#!/usr/bin/env bash

# Copyright 2017 The Fuchsia Authors
#
# Use of this source code is governed by a MIT-style
# license that can be found in the LICENSE file or at
# https://opensource.org/licenses/MIT

set -eo pipefail

usage() {
  echo "usage: ${0} [options] {arm64, x64}"
  echo
  echo "  -b [branch]     Remote branch of zircon-guest linux repository to"
  echo "                  pull before building (default: machina)."
  echo "  -d [defconfig]  Linux config (default: machina_defconfig)."
  echo "  -l [linux-dir]  Linux source dir."
  echo "  -o [image]      Output location for the built kernel."
  echo
  exit 1
}

while getopts "b:d:l:o:" OPT; do
  case $OPT in
  b) LINUX_BRANCH="${OPTARG}";;
  d) LINUX_DEFCONFIG="${OPTARG}";;
  l) LINUX_DIR="${OPTARG}";;
  o) LINUX_OUT="${OPTARG}";;
  *) usage;;
  esac
done
shift $((OPTIND - 1))

declare -r LINUX_DIR=${LINUX_DIR:-/tmp/linux}
declare -r LINUX_DEFCONFIG=${LINUX_DEFCONFIG:-machina_defconfig}

declare -rx KBUILD_BUILD_USER="machina"
declare -rx KBUILD_BUILD_HOST="fuchsia.com"

case "${1}" in
arm64)
  type aarch64-linux-gnu-gcc-9 ||
    { echo "Required package gcc-aarch64-linux-gnu-9 is not installed."
      echo "(sudo apt install gcc-aarch64-linux-gnu-9)"; exit 1; }

  declare -rx ARCH=arm64
  declare -x CROSS_COMPILE=aarch64-linux-gnu-
  declare -r LINUX_IMAGE="${LINUX_DIR}/arch/arm64/boot/Image";;
x64)
  declare -rx ARCH=x86_64
  declare -x CROSS_COMPILE=x86_64-linux-gnu-
  declare -r LINUX_IMAGE="${LINUX_DIR}/arch/x86/boot/bzImage";;
*)
  usage;;
esac

# Current default branch isn't compatible with gcc10
declare -x CC=${CROSS_COMPILE}gcc-9

if [ -n "${LINUX_BRANCH}" ]; then
  # Shallow clone the repository.
  if [ ! -d "${LINUX_DIR}/.git" ]; then
    git clone --depth 1 --branch "${LINUX_BRANCH}" https://zircon-guest.googlesource.com/third_party/linux "${LINUX_DIR}"
  fi

  # Update the repository.
  pushd "${LINUX_DIR}"
  if [[ `git branch --list ${LINUX_BRANCH} ` ]]; then
    git checkout ${LINUX_BRANCH}
    git pull --depth 1 origin ${LINUX_BRANCH}
  else
    git fetch --depth 1 origin ${LINUX_BRANCH}:${LINUX_BRANCH}
    git checkout ${LINUX_BRANCH}
  fi
  popd
fi

# Build Linux.
pushd "${LINUX_DIR}"
# CC must be specified on the command line to override the setting in Makefile
make CC=${CC} "${LINUX_DEFCONFIG}"
make CC=${CC} -j $(getconf _NPROCESSORS_ONLN)
popd

if [ -n "${LINUX_OUT}" ]; then
  mkdir -p $(dirname "${LINUX_OUT}")
  mv "${LINUX_IMAGE}" "${LINUX_OUT}"
fi