#!/bin/bash

# Copyright 2016 Matthew Thode
# All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.

if [ "${DIB_DEBUG_TRACE:-0}" -gt 0 ]; then
    set -x
fi
set -eu
set -o pipefail

[ -n "${ARCH}" ]
[ -n "${TARGET_ROOT}" ]

if [ 'amd64' = "${ARCH}" ] ; then
    ARCH='x86_64'
fi

if ! [ 'x86_64' = "${ARCH}" ] ; then
    echo "Only x86_64 images are currently available but ARCH is set to ${ARCH}."
    exit 1
fi

# valid gentoo profiles are as follows
# default/linux/amd64/13.0
# default/linux/amd64/13.0/no-multilib
# hardened/linux/amd64
# hardened/linux/amd64/no-multilib
GENTOO_PROFILE=${GENTOO_PROFILE:-'default/linux/amd64/17.0'}
if [[ "${GENTOO_PROFILE}" == "default/linux/amd64/17.0" ]]; then
    FILENAME_BASE='gentoo-stage4'
    SIGNED_SOURCE_SUFFIX='minimal'
elif [[ "${GENTOO_PROFILE}" == "default/linux/amd64/17.0/no-multilib" ]]; then
    FILENAME_BASE='gentoo-stage4-nomultilib'
    SIGNED_SOURCE_SUFFIX='minimal-nomultilib'
elif [[ "${GENTOO_PROFILE}" == "hardened/linux/amd64" ]]; then
    FILENAME_BASE='gentoo-stage4-hardened'
    SIGNED_SOURCE_SUFFIX='hardened+minimal'
elif [[ "${GENTOO_PROFILE}" == "hardened/linux/amd64/no-multilib" ]]; then
    FILENAME_BASE='gentoo-stage4-hardened-nomultilib'
    SIGNED_SOURCE_SUFFIX='hardened+minimal-nomultilib'
else
    echo 'invalid profile, please select from the following profiles'
    echo 'default/linux/amd64/17.0'
    echo 'default/linux/amd64/17.0/no-multilib'
    echo 'hardened/linux/amd64'
    echo 'hardened/linux/amd64/no-multilib'
    exit 1
fi

DIB_CLOUD_SOURCE=${DIB_CLOUD_SOURCE:-"http://distfiles.gentoo.org/releases/amd64/autobuilds/latest-stage4-amd64-${SIGNED_SOURCE_SUFFIX}.txt"}
BASE_IMAGE_FILE=${BASE_IMAGE_FILE:-"http://distfiles.gentoo.org/releases/amd64/autobuilds/$(curl ${DIB_CLOUD_SOURCE} -s | tail -n 1 | cut -d\  -f 1)"}
SIGNATURE_FILE="${SIGNATURE_FILE:-${BASE_IMAGE_FILE}.DIGESTS.asc}"
CACHED_FILE="${DIB_IMAGE_CACHE}/${FILENAME_BASE}.tar.bz2"
CACHED_SIGNATURE_FILE="${DIB_IMAGE_CACHE}/${FILENAME_BASE}.asc"

if [ -n "${DIB_OFFLINE}" -a -f "${CACHED_FILE}" ] ; then
    echo "Not checking freshness of cached ${CACHED_FILE}"
else
    echo 'Fetching Base Image'
    "${TMP_HOOKS_PATH}"/bin/cache-url "${SIGNATURE_FILE}" "${CACHED_SIGNATURE_FILE}"
    "${TMP_HOOKS_PATH}"/bin/cache-url "${BASE_IMAGE_FILE}" "${CACHED_FILE}"
    pushd "${DIB_IMAGE_CACHE}"
    # import the key
    # this key can be verified at one of the following places
    # https://wiki.gentoo.org/wiki/Project:RelEng#Keys
    # https://dev.gentoo.org/~dolsen/releases/keyrings/gentoo-keys-*.tar.xz
    # http://distfiles.gentoo.org/distfiles/gentoo-keys-*.tar.xz
    GPGDIR=$(mktemp -d -t)
    gpg --no-default-keyring --keyring "${GPGDIR}"/gentookeys.gpg --import "${TMP_HOOKS_PATH}"/extra-data.d/gentoo-releng.gpg
    # check the sig file
    gpgv --keyring "${GPGDIR}"/gentookeys.gpg "${CACHED_SIGNATURE_FILE}"
    if [[ "${?}" != 0 ]]; then
        echo 'invalid signature file'
        exit 1
    fi
    rm -rf "${GPGDIR}"
    echo 'valid key used'
    CACHED_SHA512SUM=$(grep -A1 -e 'SHA512' "${CACHED_SIGNATURE_FILE}" | grep -e 'tar.bz2$' | cut -d\  -f 1)
    ACTUAL_SHA512SUM=$(sha512sum "${CACHED_FILE}" | cut -d\  -f 1)
    if [[ "${ACTUAL_SHA512SUM}" != "${CACHED_SHA512SUM}" ]]; then
        echo "invalid checksum on downloaded tarball: ${CACHED_FILE}"
        exit 1
    fi
    echo 'valid checksum'
    popd
fi

# Extract the base image (use --numeric-owner to avoid UID/GID mismatch between
# image tarball and host OS)
sudo tar -C "${TARGET_ROOT}" --numeric-owner --xattrs -xjpf "${CACHED_FILE}"