#!/bin/bash
# Copyright 2017 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

SCRIPT_ROOT=$(dirname "$(readlink -f "$0")")
. "${SCRIPT_ROOT}/build_library/build_common.sh" || exit 1
. "${SCRIPT_ROOT}/build_library/filesystem_util.sh" || exit 1

assert_inside_chroot "$@"

DEFINE_string arch "amd64" \
  "Architecture of the VM image"
DEFINE_string filesystem "ext4" \
  "Filesystem for the rootfs image"
DEFINE_string image "" \
  "Chromium OS disk image to build the Termina image from"
DEFINE_string output "" \
  "Output directory"

FLAGS_HELP="USAGE: ${SCRIPT_NAME} [flags]

To build a tatl test image, try:
$ ./build_image --board=tatl test
$ ${SCRIPT_NAME} --image=../build/images/tatl/latest/chromiumos_test_image.bin --output=tatl
"
FLAGS "$@" || exit 1
eval set -- "${FLAGS_ARGV}"
switch_to_strict_mode

get_version() {
  local output_dir="$1"
  awk -F'=' -v key='CHROMEOS_RELEASE_VERSION' '$1==key { print $2 }' \
    "${output_dir}"/lsb-release
}

read_le_int() {
  local disk="$1"
  local offset="$2"
  local size="$3"

  case "${size}" in
  1 | 2 | 4 | 8)
    ;;
  *) die "${size} is not a valid int size to read"
    ;;
  esac

  local raw="$(xxd -g ${size} -e -s ${offset} -l ${size} ${disk} | cut -d' ' -f2)"
  local result="$(( 16#${raw} ))"

  echo "${result}"
}

extract_squashfs_partition() {
  local src_disk="$1"
  local src_part="$2"
  local dst_file="$3"

  local part_start_blks="$(cgpt show -i "${src_part}" -b "${src_disk}")"
  local part_start_bytes="$(( part_start_blks * 512 ))"
  local part_size_blks="$(cgpt show -i "${src_part}" -s "${src_disk}")"
  local part_size_bytes="$(( part_size_blks * 512 ))"

  # To be sure we're extracting a squashfs partition, verify the magic.
  # See fs/squashfs/squashfs_fs.h.
  local magic="$(read_le_int ${src_disk} ${part_start_bytes} 4)"
  if [[ "${magic}" -ne 0x73717368 ]]; then
    die "Partition ${src_part} doesn't look like a squashfs partition"
  fi

  dd if="${src_disk}" of="${dst_file}" skip="${part_start_bytes}c" \
    count="${part_size_bytes}c" iflag=skip_bytes,count_bytes
}

can_hardlink() {
  local file1=$1
  local file2=$2

  # The file is considered hard-linkable if the access rights, user, and group
  # are the same.
  [[ "$(sudo stat -c '%a' ${prev_line})" = "$(sudo stat -c '%a' ${line})" ]] && \
     [[ "$(sudo stat -c '%u' ${prev_line})" = "$(sudo stat -c '%u' ${line})" ]] && \
     [[ "$(sudo stat -c '%g' ${prev_line})" = "$(sudo stat -c '%g' ${line})" ]]
}

do_hardlinks() {
  local dir=$1

  local line prev_line=""
  if [ -z $(command -v fdupes) ]; then
    warn "Please install fdupes for removing dups"
  fi
  while read line; do
    # Treat the first file as the original.
    if [[ -n "${prev_line}" && -n "${line}" ]]; then
      if can_hardlink "${prev_line}" "${line}"; then
        sudo ln -f "${prev_line}" "${line}"
      fi
    fi

    prev_line="${line}"
  done < <(sudo fdupes --recurse ${dir})
}

# Repack termina rootfs.
repack_rootfs() {
  local output_dir="$1"
  local fs_type="$2"
  local arch="$3"
  local rootfs_img="${output_dir}/vm_rootfs.img"
  local stateful_img="${output_dir}/vm_stateful.img"

  # Create image in a temporary directory to avoid the need for extra space
  # on the final rootfs.
  local rootfs="${output_dir}/rootfs"
  local stateful="${output_dir}/stateful"

  sudo unsquashfs -d "${rootfs}" "${rootfs_img}"
  sudo unsquashfs -d "${stateful}" "${stateful_img}"

  # Remove source images.
  sudo rm -f "${rootfs_img}" "${stateful_img}"

  # Fix up rootfs.

  # Remove efi cruft.
  sudo rm -rf "${rootfs}/boot"/{efi,syslinux}
  # Don't need firmware if you don't have hardware!
  sudo rm -rf "${rootfs}/lib/firmware"
  # Get rid of stateful, it's not needed on termina.
  sudo rm -rf "${rootfs}/mnt/stateful_partition"
  # Create container stateful and shared dirs.
  sudo mkdir "${rootfs}"/mnt/{stateful,shared}
  # Copy the dev_image into its location at /usr/local.
  sudo cp -aT "${stateful}"/dev_image "${rootfs}/usr/local"

  if [[ "${arch}" == "arm" ]]; then
    cp "${rootfs}"/boot/Image-* "${output_dir}/vm_kernel"
  else
    cp "${rootfs}"/boot/vmlinuz "${output_dir}/vm_kernel"
  fi

  # Remove vmlinuz from the rootfs; it's not necessary.
  sudo rm -rf "${rootfs}"/boot/vmlinuz*

  do_hardlinks "${rootfs}"

  sudo cp "${rootfs}/etc/lsb-release" "${output_dir}/lsb-release"
  sudo cp "${rootfs}/opt/google/chrome/resources/about_os_credits.html" \
      "${output_dir}/about_os_credits.html"

  case "${fs_type}" in
  squashfs)
    sudo mksquashfs "${rootfs}" "${rootfs_img}" -comp lzo
    ;;
  ext4)
    # Start with 110% rootfs size, then shrink.
    local image_size=$(sudo du -sxm "${rootfs}" | awk '{print $1}')
    let image_size=image_size*11/10
    truncate --size "${image_size}M" "${rootfs_img}"
    /sbin/mkfs.ext4 -F -m 0 -i 16384 -b 4096 -O "^has_journal" "${rootfs_img}"
    local rootfs_mnt="$(mktemp -d)"
    fs_mount "${rootfs_img}" "${rootfs_mnt}" ext4 rw
    sudo cp -aT "${rootfs}" "${rootfs_mnt}"
    fs_umount "${rootfs_img}" "${rootfs_mnt}" ext4 rw
    # Shrink to minimum size.
    /sbin/e2fsck -f "${rootfs_img}"
    /sbin/resize2fs -M "${rootfs_img}"
    rmdir "${rootfs_mnt}"
    ;;
  *)
    die_notrace "Unsupported fs type ${fs_type}."
    ;;
  esac

  sudo rm -rf "${rootfs}" "${stateful}"
}

main() {
  if [[ -z "${FLAGS_image}" ]]; then
    die_notrace "Please provide an image using --image"
  elif [[ ! -f "${FLAGS_image}" ]]; then
    die_notrace "'${FLAGS_image}' does not exist"
  fi

  if [[ "${FLAGS_arch}" != "amd64" && "${FLAGS_arch}" != "arm" ]]; then
    die_notrace "Architecture '${FLAGS_arch}' is not valid. Options are 'amd64' and 'arm'"
  fi

  case "${FLAGS_filesystem}" in
  squashfs|ext4)
    ;;
  *)
    die_notrace "Filesystem '${FLAGS_filesystem}' is not valid. Options are 'squashfs' and 'ext4'"
    ;;
  esac

  if [[ -z "${FLAGS_output}" ]]; then
    die_notrace "Output directory was not specified"
  elif [[ -e "${FLAGS_output}" ]]; then
    die_notrace "${FLAGS_output} already exists"
  fi

  local output_dir="${FLAGS_output}"
  local stateful_img="${output_dir}/vm_stateful.img"
  local rootfs_img="${output_dir}/vm_rootfs.img"
  local image="${FLAGS_image}"

  mkdir -p "${output_dir}"
  extract_squashfs_partition "${image}" "3" "${rootfs_img}"
  extract_squashfs_partition "${image}" "1" "${stateful_img}"

  repack_rootfs "${output_dir}" "${FLAGS_filesystem}" "${FLAGS_arch}"

  info "Done! The resulting image is in '${output_dir}'"
}

main "$@"